Love how you always diagnose unusual problems and explain why you are doing a particular "trial" in attempting to isolate the root cause of the failure.
The issue with the clutch is that the pins the shoes pivot on are rusted into the shoes, you need to punch out the pins and remove the rust to allow the shoes to pivot nicely.
Lets not pretend like nobody saw the little bulldozer and and track loader in the outro. Are those future projects by any chance? Love your videos, you are doing a fantastic job.
This video was incredibly well done. I appreciated getting to see your entire diagnostic process and your skill in taking apart and reassembling all the parts. What I liked best is your ability to teach how each part functions as you went thru the process. Most of us would never have access to this level of expertise at our local small engine repair shops. Thanks so much.
I really like my Stihl equipment - have always been a Stihl guy, owned half a dozen saws and several trimmers including a 2 stroke kombi system setup. My only real complaint was the carb on my MS-180 saw, replaced it with one that could actually be tuned and it runs way better. The rest have been great. Their low end homeowner products are way better than any of the other low cost competitors!
Great to see your process but you should check the hole in the cover plate where the cam gear shaft rides. It opens out letting the shaft wobble causing it to wear early. That's what happened to my 131 so I had to replace the plate as well.
That's pretty interesting. I have a KM-56-R powerhead and those same attachments, plus an edger. It's a nice little system. The KM-56-R is a true 2-cycle, but I had to go pull the engine diagrams to confirm that. I never looked too closely at it because it's always just run :)
As a Stihl dealer and small engine mechanic, I can tell you I have seen this all to often. Most of the time’s it happens because d valve clearance isn’t checked/adjusted often enough. I Alwas recommend to check the valve clearance at least annually. Ore the ,,hammering” of the those shoes that ride in the Cam, will destroy it…… The reason why they made it out of Plastic in the first place, is because of lubrication. Greatings to you and anyone how reads this: Jan from Switzerland PS: There may be some grammar error’s in this text, English isn’t my strongest language 😅
@Jan, I am not convinced of this explanation - why would hammering make it wear all the knob down in one catastrophic event as explained by Jon? It makes no logical sense. I would suspect either lack of lubrication or over-heating. One could amplify the other. "Plastic" obviously does not support overheating together with mechanical stress. Could misadjusted valves mean higher operating temperature? Was the machine running extra hot when you used it Jon?
Sorry Still dealer but there is absolutely no reason other than cheap out (or turning more pieces per the same time spend to make one in Brass, since with injection moulding you can pump let's say 10 per cycle while you make one on a CNC) for that cam being made of plastic other than a metal. Don't want to make it so good that it doesn't go bad anytime right, or the after sales would lose profit and new sales also drop since why I would buy a new one if my old 20 year something still runs like a champ?
Why would a company that has been the Mercedes of small industrial engine quality elect to build an engine with plastic cams? I have a 22 year old Ryobi 4 stroke 845r 25 cc 4 stroke engine that finally wore out after 22 years of pretty steady use and it wasn't the cam it was the flywheel, you cannot find replacements for these once the keyway wears out. Nowadays Ryobis have plastic cams and their cams are OHC where all the engine heat is, in the head. Why Stihl didn't take Honda's little GX 4 stroke engine tech to heart is a head scratcher. I also have a Honda GX31 pump engine I bought used in 1998 and it still runs like the day it was made.
I agree with ya bud i do think his oil has been pretty sub par aswell Small engines mech 30 years here. Normal ill see pitting and the comp release failed never seen a melted one that bad. In the fleet i work on we have 40 + of these units.
I used to work with a light 2 stroke Stihl about 30 years ago. It was a brush cutter, not a combi tool. It was great! Also the duo handle bars on that machine work way better for the long term. But maybe not that handy when using the saw 😉 Great video.
Nice fix, the early honda gx25 engines had a similar problem when run to hot the plastic cam melted, they changed from gear driven to notched belt driven cam. Also Stihl uses they're own brand of Dirko sealant which is also orange (easily mistaken for rtv) but looking at the crankcase when you took it apart i'd say someone has been in there before, i've never seen Stihl use overkill amounts like that. When it comes to you're clutch there are crush tubes in the pivoting ends of the shoes that are frozen in place (hence clutch will only work with bolts loose) you need to free up those crush tubes in the shoes. if you leave it the way it is it will ware through the bolts and cause more damage!! Good luck with it, thanks for posting!
We use Stihl since at least 2001. We have multiple saws, Weadaeters/Brushcutters, hedgetrimmers and leafblowers. We never had any Stihl related problems, most of them were my dads and granddads user errors. So all in all we are quite happy with them. The biggest problem is that the plastic and rubber parts start to dissolve and dont work as intended
I have two FS90s (one in service, one not) that have the same engine. It's highly likely that I don't have nearly the same hours on either that you have on this unit, but this sure makes me want to take them apart and check on that plastic cam. Thank you for the in-depth coverage.
I was told by a lawn mower repair shop never use starting fulid in a motor that uses fule/oil mix, the reason is the cylinder walls are coated with Teflon and starting fulid breaks down that material making it soft so when the rings pass by the weak spot it tears it off the cylindef walls effectively trashing the motor.
This is why most people just buy a new tool. I would never get all the parts back in place and eventually end with it in the scrap pile. Thanks for the tutorial & the explanation of all the functions. The camera angle was great. I was right up in there the whole time. Thanks!
Great video! I have a Stihl 2stroke brush cutter but have just recommended a four stroke to a friend but with reservations because of that cam wheel. Not a big deal to replace though and your 'explain as you go' style is very user friendly! :)
Always been a big fan of stihl products. Strange there was so much RTV in the crank but glad you were able to get it sorted out. Very interesting to watch!
Interesting to see one of those little Stihl 4 mix motors disassembled. I’ll keep my Stihl 2 strokes! Also I love the new thermal imager you showed using your lift to demonstrate. 👍🏻
Great work! I always learn so much from you! And.. if one of those cows got much closer to the fire, y’all would have had some bbq for dinner! Thanks for all your content!
I have a Honda and the cam is the same design, you don't have to mix oil with fuel it has an oil res with a rotor that whips air into it then the crank has a hole that draws the oil in with the pos and neg pressure, then pumps it through a reed valve into the cam area up into the valve cover and then drains back to the oil res. great videos you have a new subscriber.
I picked up a broken FS-90 a few years ago which has the same exact power head assembly, someone had stepped on it and broken 2 of the tabs off of the bottom case which support the shaft so I had to do a full engine tear down to replace the broken stuff. My local dealer was really helpful, they sold me that $20 tube of OEM Stihl "Dirko HT" RTV to put everything back together and one of the repair techs warned me not to use to much like Stihl does sometimes because the pieces will eventually get into the engine and do exactly what you're repairing. Pieces get into the gap and wear down the plastic cam gear.
MAKE SURE you use the Sthl oil in those 4mix engines. They require special oil or you’ll wear the cam and the bearings early. There’s other videos on this subject.
Lies. Oil and fuel is just that. Higher or lower octanes and more or less oil is really the only differences you can make. Stihl oil when burnt burns almost to like a yellow o believe so if you use a different kind of oil in it when they check your warranty they look to see the oil you've been using has been burning yellow in the exhaust/muffler. They don't add some special additives or nothing it's just marketing.
@Steve just Steve never use ethanol gas and use 91 when mixing and you'll never have any issues starting or running and it can sit all winter pick it up next summer it'll fire right up. Non ethanol gas doesn't break down like corn gas does. And your fuel lines won't get brittle.
@@shaynewalker4519 it’s actually is very true. The 4 mix engines require some wear additives in the oil to help lubricate the piston pin bearing which in that engine is a normal bushing, not a needle bearing. It also needs the additives to prevent wear on the cam shaft. You are correct about the non ethanol gas though. My cheap Ryobi string trimmer starts on the first pull with ethanol free gas.
Whatever the end result (I’m half way through the video), I very much admire your thoughtful consideration of the scenarios and advantages and disadvantages of the design. It really shows a powerful intellect that you consider the different views …and help us see them along the way. It keeps bringing me back to these videos . Keep being awesome.
Have exactly the same model and 2010 year of manufacture. No issues with it apart from erratic idling. Start it up and its ticking over way to fast activating the clutch, back it down to stop clutch biting and its fine till you leave it for a couple of weeks, then it wont idle at all till you increase it and it runs ok. Then a couple of weeks later, the clutch engages again...lol/cry.
I have a stihl 170 trimmer and after I got it home, I thought boy it pulls hard. I took it back to the dealer and they said that's how they are. So i messed with the timing and it is much easier to pull to start! I've had mine since 2014 and when it runs will cut weeds like crazy. Last year it started running not so good and I bought a new one a 90 or 91 can't remember but it is good enough.
You were almost right you need to take the bushings out of the clutch shoes. They are not supposed to be seized that’s supposed to spin freely. And your bolts are supposed to be blue, loctited and tight. I still love the videos keep them coming.
I've recently repaired a FS 110 and a FS 130 by replacing the cam gear, not because the gear was damaged but due to the molded metal plate on the back of the plastic gear separating and allowing the fly weight to move thus throwing the timing off.
The crankcase is often used as part of the intake on small 2 strokes, you have side wall vales that open/close to draw in the air fuel mixture. They do this to lubricate the crank
The crankcase is attached to the intake port through the valve cavity, which causes it to be similar to a traditional 2 stroke where the piston dropping in the bore helps push some mixture into the cylinder. The lower attachment from the crankcase to the carb is to help pump fuel, since the intake pulses only happen half as often as a 2 stroke, and aren't as strong.
I have a Stihl weed wacker but i just got fed up with it and got my self a AL-KO BC 500 B that thing is a bit hard to start cause it got no decompresor but it runs like a dream and it works when i need it and it puts Stihl to shame both in power and fule tank size.
I have a small engine shop. I specialize in 4mix equipment. These only wear down like this when there's not enough oil or there's an air leak which causes oil starvation on the bottom end. Normally, the main wear on the cams is actually cavitation holes. Stihl originally tried several materials for these cam wheels and found that this nylon composite worked longer than the metal versions. By the way, the reason your clutch is acting up is because you didn't press out the bushings. They get rusted and expand. They aren't supposed to be tight.
man thanks a lot for this video I have one all apart and was at a dead end on why it would not run , I did not check the cam lift but knew i was missing something and i even noticed there was mor to the cam gear than just a gear but didnt want to go there if i would have i would have seen it ha that's what i get thanks again ! -John in Texas
Yes I think Sthil quality is definitely going downhill recently. They want to decrease costs and raise prices in the last couple years. Hope they can turn it around and get back on track but they may be headed for a downfall like so many other brands have fallen victim too due to greed.
Hi nice work, Stihl have a new mod for the timing cover which has a flow director so the camshft gets better lubrication so maybe they do listen, keep up the great work and share so we can all learn Jutty
I have the exact unit and have been pleased with it. I will not use a weed eater , the pole saw and blower are used a lot around my place . Roundup and 24d are my substitute for a weed eater. I agree the combi unit don’t match up to the professional line. It does just fine for what I need.
I was thinking the same thing as you were talking about the cam gear I would keep you old cam gear measure the new dimensions and make a sleeve to press fit on to the gear you would have to put the gear in the freezer an heat the brass up no reason it shouldn’t work.
Hi John can i make sum tips . The vales and cam timeing and adjusting must be set by an arrow on flywheel that goes to the last screw on the coil that is for timing and adjusting point.the clutch bushings have seized in the shoe clean and grease. The gasket sealer is not ment for aluminium it is stihl sealer hope this helps. All best Keith
Do you run ethanol fuel? I am wondering if that cam gear may not be tolerant of ethanol. I know other manufactures had a lot of issues when the E10 was first introduced. I actually have a Tecumseh ethanol test kit that was a service tool they issued in the 90's to figure out what percentage ethanol was in the fuel of the engines where they were getting premature failure.
Congrats with yet another popcorn-worthy video. I´m starting to look forward to fridays like when I was a kid waiting for the next episode of my favorite show. (My kids have no idea what I´m talking about of course...)
As i understand you should have had a lot of valve gap at the rocker with worn out cam lobe. But you had tight clearance,so i think the lack of gap melted the plastic : the constant drag didn't allow a lubrication and caused heat by friction,not the silicone. You need more frequent valve lash verifications. For torque specs : check bolt grade,and its thread pitch (imperial,or metric) ,then look for a table sheet with normalized torque specs on internet. It's normalized,so you can't really make a mistake. It works for about everything.
Those two pins that the cam wheel and rocker arms ride on are the nemesis of the Stihl 4mix brushcutter engines. The seat of the pin for the cam becomes oval on the engine block and the seat of the pin for the valve rockers become oval on the cover. After that the valve clearance will vary and one will tend to over adjust , this will cause the cam followers to dig into the plastic of the cam. These pin seats need to be repaired with small sleeves. Except for this issue these engines are real jewels and i still have the 100 and 130 engines from more than two decades ago
Makes perfect sense why it failed I think it got so hot it started making the rtv almost liquid and then the clog happened then the melting of the cam gear
John I have two engines that will not throttle up. I thought it was carburetor jets but I'm going to look at the valves and if there is minimal movement a worn cam lobe might be the problem. Thanks David
Unless as he mentioned plastic was used on purpose to make this the sacrificial part. It will fail first before any other part is damaged thus protecting the whole engine. Plus it is easy to replace. Only issue if they are jerks and charge an arm and a leg for the replacement part when they DESIGNED it to break.
@@nostromo526 People just seem to assume that because something is plastic that it was made to be cheap, rather than for some other reason. Same people probably think the shear pins in the collapsible steering shafts should be steel instead of soft plastic :)
*hah, wrote this comment just before the part in the vid* Pretty neat the plastic cam has a built in decompressor it seams, the little metal plate on the back side, and small metal pin protruding from the lobe at one position, whole thing must run centrifugally and deactivate at idle+ speeds... I guess very much a comfort feature, as overcoming the compression isn't too hard, but i guess makes a more 'luxury' product...
I miss my Weed Eater Model GTI 15T. This was back in the day when things were made a lot better than today's stuff. I had my FS 94 R serviced twice due to carb problem and FS-40 C E with issues.
10 years of service ! no bad I bought a 2 HP chinese made trimmer new and only lasted three months !! 😆😆😆 the guy who was going to fix it told me you are going to spend in parts almost the same you spend for it !! my advice is buy from a well known brand , a machine that will last or give at least 5 years of service is worth every penny !! .
Oil and air mix must be drawn into crankcase and then up into the cylinder through a port and the inlet valve, so very similar to two stroke. This also means pulsing effect of crankcase can be used for the fuel pump in the carb. Cam wear would mean low air flow through engine and low pumping affect for the carb fuel pump. A double whammy. Advantage engine could run at extreme angles as no oil in a sump and four stroke is quieter and more fuel efficient typically than a two stroke. So lower emissions.
Great hands on learning video, thought at the start of the video that i was getting floaters in my eys till i realized it was bugs flying around in front of the camera lol. Was wondering if when you where cutting that monsterous tap root that it jammed up for a few seconds and caused the plastic timing gear to seize for a few seconds, should have had lubrication but it looks like your lobe melted down some. Maybe the valve and push rods got jammed by som we thing and pressure on the cam gear lobe caused it to melt a little. Love your videos keep it up.
The 4 mix do require a bit more maintenance...good oil, good mix, adjusted valve lash. If you don't do those things, the plastic cam gear will burn up. But the 4 mix make great power and with less fumes. I run the fs91, fs111 and fs131. The 131 is a powerful sucker.
Last year i bought a stihl fs90r for 100 dollars from a friend that didn't run and it felt like it had no compression so i got concerned but i took it apart and the cam was worn to hell and the piston is completely fine so after buying a cam gear from stihl and it works great
Enjoyable video! Too bad the fuel mix in a four- stroke confuses some folks. I first noticed this when a friend of mine had a new pole saw marked "4-Mix" and I questioned him what that meant. He didn't know the difference between 2 and 4-stroke engines, so the uniqueness of this was lost on him. He was just lucky he got the right fuel - or the dealer helped him out. He actually bought pre-mixed fuel! Anyways, I have a number of 4-stroke model airplane engines that use mixed fuel and use it to lube the bottom end. I think some unburned oil also gets past the rings and helps the lower end that way. I do believe I've seen a passageway from the inlet to the crankcase as you described. I have seen a Troy-Bilt string trimmer that has oil in the crankcase - but it had no carb adjustments beyond idle speed.
I would bet that what you think was rtv is really a rubber one way valve for your primer bulb , there is a really Good channel with great videos on 2 cycle carbs vintage engine repair is the channel . I could have missed seeing it in your first video i guess . The other guy is even better The Repair Specialist .
I've had the weirdest problems with a 4-mix Stihl chainsaw, it would start ok but when trying to accelerate hard, it would kind of choke out and end up stalling. Slowly accelerating up would work okay-ish though and no amount of messing with the setting screws would help. Now it works very nicely and I have no idea why
This videos are going to be GOLD when all these machines are electric...(like my dad that had a very minute steam engine). Basically all engines are Cuckoo clocks and electric is quartz watch !
I hope that one day you have an comment review and see this comment☺️your video's always come out when its raining where i live and watching your videos always bring a good mood and i can say that i learn something in EVERY video of you
hiya - if you have a 3D printer - you could print a new cam, then use that to make a mould and recast the cam cog part in brass :) Also you could use the lost foam process if you don;t have a 3D printer. UPDATE - I was watching when i said that - so I subsequently heard you saying you'd make a brass copy yourself :)
I design large diesel engines for a living...these little single cylinders amaze me with their use of very simple mechanisms like that compression release. Those cam followers are like toothpicks in my world.
I think the exact thing you lost is cooling, because by using the gas as coolant in the engine you have a huge cooling power: the hot gas get burnt and exhansted, only cool stuff gets in. But also, when you water cool an engine, you never boil the water, but in your system you can boil the gas, that means that there is extra energy absorbsion by the boiling. it's really regenerative cooling rocket engine territory. thanks for the video, I had a lot of questions when you described the lack of oiling system, and everything got answered later.
Howdy, (from AUS) love your work, this was one of my fav videos in a while. Love the way you time lapse, we don't need to see every screw turned. My theory, what sort of fuel do you use there in the USA, is there any ethanol involved,? Maybe it affected the plastic?? Also, are you using Sthil synthetic oil? my dealer told me it was far superior. Keep up the good work, one of the better videos on you tube, I am a fan. Cheers Rick
did you check the spark arrestor, if its clogged it can bog down the engine, just remove the mesh screen from exhaust and clean using carb cleaner and fine little brush and then blow dry with compressed air and refit. should bring the engine back to life
This sounds like a good thing. It went into "limp home" mode, saving the rest of the motor. The big end bearing looked bad, for a tiny motor. Check the mains, as well ?
38:20 You should see the valvetrain in my OS FS-26 Surpass. That engine is only one fourth of a cubic inch in displacement! The pushrods are LITERALLY no thicker than a spaghetti noodle.
I believe this engine is a 4 stroke which does NOT use use oil from the fuel to lubricate the crank but has a separate oil supply. The fuel for this engine has no oil, I can only assume you lost the oil in the sump ted north
Love how you always diagnose unusual problems and explain why you are doing a particular "trial" in attempting to isolate the root cause of the failure.
Ummm I don’t think he found any roots causing the problem 😅😅😅
@@TomTom-tg2cb running lean could cause all sorts of problems. as does killing a saw with the choke because the killswitch does not work.
@@TomTom-tg2cb LOL 😅
The issue with the clutch is that the pins the shoes pivot on are rusted into the shoes, you need to punch out the pins and remove the rust to allow the shoes to pivot nicely.
Lets not pretend like nobody saw the little bulldozer and and track loader in the outro. Are those future projects by any chance? Love your videos, you are doing a fantastic job.
Well spotted. 👍👍
In his winch video he also loaded like a six wheeled utility vehicle onto his trailer which I thought would be part of the future content.
Man I'm excited to see all 3 of those on the channel. I was stoked to see them
@@wg8304 It will. Just aren't enough hours in a day!
@@FarmCraft101 Hey, there's hours at night as well and sleep is over rated. 😁
This video was incredibly well done. I appreciated getting to see your entire diagnostic process and your skill in taking apart and reassembling all the parts. What I liked best is your ability to teach how each part functions as you went thru the process. Most of us would never have access to this level of expertise at our local small engine repair shops. Thanks so much.
I really like my Stihl equipment - have always been a Stihl guy, owned half a dozen saws and several trimmers including a 2 stroke kombi system setup. My only real complaint was the carb on my MS-180 saw, replaced it with one that could actually be tuned and it runs way better. The rest have been great. Their low end homeowner products are way better than any of the other low cost competitors!
Great to see your process but you should check the hole in the cover plate where the cam gear shaft rides. It opens out letting the shaft wobble causing it to wear early. That's what happened to my 131 so I had to replace the plate as well.
That's pretty interesting. I have a KM-56-R powerhead and those same attachments, plus an edger. It's a nice little system. The KM-56-R is a true 2-cycle, but I had to go pull the engine diagrams to confirm that. I never looked too closely at it because it's always just run :)
As a Stihl dealer and small engine mechanic, I can tell you I have seen this all to often. Most of the time’s it happens because d valve clearance isn’t checked/adjusted often enough. I Alwas recommend to check the valve clearance at least annually. Ore the ,,hammering” of the those shoes that ride in the Cam, will destroy it…… The reason why they made it out of Plastic in the first place, is because of lubrication.
Greatings to you and anyone how reads this: Jan from Switzerland
PS: There may be some grammar error’s in this text, English isn’t my strongest language 😅
@Jan, I am not convinced of this explanation - why would hammering make it wear all the knob down in one catastrophic event as explained by Jon? It makes no logical sense.
I would suspect either lack of lubrication or over-heating. One could amplify the other. "Plastic" obviously does not support overheating together with mechanical stress.
Could misadjusted valves mean higher operating temperature?
Was the machine running extra hot when you used it Jon?
Sorry Still dealer but there is absolutely no reason other than cheap out (or turning more pieces per the same time spend to make one in Brass, since with injection moulding you can pump let's say 10 per cycle while you make one on a CNC) for that cam being made of plastic other than a metal.
Don't want to make it so good that it doesn't go bad anytime right, or the after sales would lose profit and new sales also drop since why I would buy a new one if my old 20 year something still runs like a champ?
Why would a company that has been the Mercedes of small industrial engine quality elect to build an engine with plastic cams? I have a 22 year old Ryobi 4 stroke 845r 25 cc 4 stroke engine that finally wore out after 22 years of pretty steady use and it wasn't the cam it was the flywheel, you cannot find replacements for these once the keyway wears out. Nowadays Ryobis have plastic cams and their cams are OHC where all the engine heat is, in the head. Why Stihl didn't take Honda's little GX 4 stroke engine tech to heart is a head scratcher. I also have a Honda GX31 pump engine I bought used in 1998 and it still runs like the day it was made.
@@heel57 Running lean cause of a chunk of rtv clogging the carb could cause it to overheat pretty quick.
I agree with ya bud i do think his oil has been pretty sub par aswell Small engines mech 30 years here. Normal ill see pitting and the comp release failed never seen a melted one that bad. In the fleet i work on we have 40 + of these units.
I used to work with a light 2 stroke Stihl about 30 years ago. It was a brush cutter, not a combi tool. It was great! Also the duo handle bars on that machine work way better for the long term. But maybe not that handy when using the saw 😉 Great video.
I tend to use separate tools for each job. My FS85r weedeater is still going strong, as is my chainsaw, blower and hedge trimmers. Love your channel.
Nice fix, the early honda gx25 engines had a similar problem when run to hot the plastic cam melted, they changed from gear driven to notched belt driven cam. Also Stihl uses they're own brand of Dirko sealant which is also orange (easily mistaken for rtv) but looking at the crankcase when you took it apart i'd say someone has been in there before, i've never seen Stihl use overkill amounts like that. When it comes to you're clutch there are crush tubes in the pivoting ends of the shoes that are frozen in place (hence clutch will only work with bolts loose) you need to free up those crush tubes in the shoes. if you leave it the way it is it will ware through the bolts and cause more damage!! Good luck with it, thanks for posting!
We use Stihl since at least 2001. We have multiple saws, Weadaeters/Brushcutters, hedgetrimmers and leafblowers. We never had any Stihl related problems, most of them were my dads and granddads user errors. So all in all we are quite happy with them. The biggest problem is that the plastic and rubber parts start to dissolve and dont work as intended
I have two FS90s (one in service, one not) that have the same engine. It's highly likely that I don't have nearly the same hours on either that you have on this unit, but this sure makes me want to take them apart and check on that plastic cam. Thank you for the in-depth coverage.
@AnabelleJoan I don’t DM scammers. Go take a long walk off a short pier.
I got this also but it is so hard to pull so i better check that compression release. Didnt know where it was so thanks for the info.
I was told by a lawn mower repair shop never use starting fulid in a motor that uses fule/oil mix, the reason is the cylinder walls are coated with Teflon and starting fulid breaks down that material making it soft so when the rings pass by the weak spot it tears it off the cylindef walls effectively trashing the motor.
This is why most people just buy a new tool. I would never get all the parts back in place and eventually end with it in the scrap pile. Thanks for the tutorial & the explanation of all the functions. The camera angle was great. I was right up in there the whole time. Thanks!
Great video as always. Thank you for turning down the volume on the noisey parts
Great job and another tool saved from the land fill. I just wish they made a small prop head attachment, so I could attach it to my canoe.
Great video! I have a Stihl 2stroke brush cutter but have just recommended a four stroke to a friend but with reservations because of that cam wheel. Not a big deal to replace though and your 'explain as you go' style is very user friendly! :)
Always been a big fan of stihl products. Strange there was so much RTV in the crank but glad you were able to get it sorted out. Very interesting to watch!
Interesting to see one of those little Stihl 4 mix motors disassembled. I’ll keep my Stihl 2 strokes! Also I love the new thermal imager you showed using your lift to demonstrate. 👍🏻
Great work! I always learn so much from you! And.. if one of those cows got much closer to the fire, y’all would have had some bbq for dinner! Thanks for all your content!
Thanks, It's fun hanging out on the farm. Big Thumbs Up.
I have a Honda and the cam is the same design, you don't have to mix oil with fuel it has an oil res with a rotor that whips air into it then the crank has a hole that draws the oil in with the pos and neg pressure, then pumps it through a reed valve into the cam area up into the valve cover and then drains back to the oil res. great videos you have a new subscriber.
I picked up a broken FS-90 a few years ago which has the same exact power head assembly, someone had stepped on it and broken 2 of the tabs off of the bottom case which support the shaft so I had to do a full engine tear down to replace the broken stuff. My local dealer was really helpful, they sold me that $20 tube of OEM Stihl "Dirko HT" RTV to put everything back together and one of the repair techs warned me not to use to much like Stihl does sometimes because the pieces will eventually get into the engine and do exactly what you're repairing. Pieces get into the gap and wear down the plastic cam gear.
MAKE SURE you use the Sthl oil in those 4mix engines. They require special oil or you’ll wear the cam and the bearings early. There’s other videos on this subject.
Lies. Oil and fuel is just that. Higher or lower octanes and more or less oil is really the only differences you can make. Stihl oil when burnt burns almost to like a yellow o believe so if you use a different kind of oil in it when they check your warranty they look to see the oil you've been using has been burning yellow in the exhaust/muffler. They don't add some special additives or nothing it's just marketing.
@@shaynewalker4519 Maybe, but working on my BR600 is such a PIA, I'll use it on the chance it makes a difference.
@Steve just Steve never use ethanol gas and use 91 when mixing and you'll never have any issues starting or running and it can sit all winter pick it up next summer it'll fire right up. Non ethanol gas doesn't break down like corn gas does. And your fuel lines won't get brittle.
@@shaynewalker4519 it’s actually is very true. The 4 mix engines require some wear additives in the oil to help lubricate the piston pin bearing which in that engine is a normal bushing, not a needle bearing. It also needs the additives to prevent wear on the cam shaft. You are correct about the non ethanol gas though. My cheap Ryobi string trimmer starts on the first pull with ethanol free gas.
Which specific type of Stihl oil do you recommend for those 4mix engines?
Whatever the end result (I’m half way through the video), I very much admire your thoughtful consideration of the scenarios and advantages and disadvantages of the design. It really shows a powerful intellect that you consider the different views …and help us see them along the way.
It keeps bringing me back to these videos . Keep being awesome.
Have exactly the same model and 2010 year of manufacture.
No issues with it apart from erratic idling. Start it up and its ticking over way to fast activating the clutch, back it down to stop clutch biting and its fine till you leave it for a couple of weeks, then it wont idle at all till you increase it and it runs ok. Then a couple of weeks later, the clutch engages again...lol/cry.
Fantastic video! I love small engine repair, and being a loyal Stihl guy, this is even better!
I have a stihl 170 trimmer and after I got it home, I thought boy it pulls hard. I took it back to the dealer and they said that's how they are. So i messed with the timing and it is much easier to pull to start! I've had mine since 2014 and when it runs will cut weeds like crazy. Last year it started running not so good and I bought a new one a 90 or 91 can't remember but it is good enough.
You were almost right you need to take the bushings out of the clutch shoes. They are not supposed to be seized that’s supposed to spin freely. And your bolts are supposed to be blue, loctited and tight. I still love the videos keep them coming.
You covered all elements of the system except the spark/mag. Very well done through video.
I've recently repaired a FS 110 and a FS 130 by replacing the cam gear, not because the gear was damaged but due to the molded metal plate on the back of the plastic gear separating and allowing the fly weight to move thus throwing the timing off.
The crankcase is often used as part of the intake on small 2 strokes, you have side wall vales that open/close to draw in the air fuel mixture. They do this to lubricate the crank
but this isn't a 2-stroke. hence the valves.
The crankcase is attached to the intake port through the valve cavity, which causes it to be similar to a traditional 2 stroke where the piston dropping in the bore helps push some mixture into the cylinder.
The lower attachment from the crankcase to the carb is to help pump fuel, since the intake pulses only happen half as often as a 2 stroke, and aren't as strong.
I immediately noticed that lip when you pulled the cam cover off and did a actual LOL. Amazing how much that cam had worn down
I have a Stihl weed wacker but i just got fed up with it and got my self a AL-KO BC 500 B that thing is a bit hard to start cause it got no decompresor but it runs like a dream and it works when i need it and it puts Stihl to shame both in power and fule tank size.
I have a small engine shop. I specialize in 4mix equipment. These only wear down like this when there's not enough oil or there's an air leak which causes oil starvation on the bottom end. Normally, the main wear on the cams is actually cavitation holes. Stihl originally tried several materials for these cam wheels and found that this nylon composite worked longer than the metal versions. By the way, the reason your clutch is acting up is because you didn't press out the bushings. They get rusted and expand. They aren't supposed to be tight.
man thanks a lot for this video I have one all apart and was at a dead end on why it would not run , I did not check the cam lift but knew i was missing something and i even noticed there was mor to the cam gear than just a gear but didnt want to go there if i would have i would have seen it ha that's what i get thanks again !
-John in Texas
Yes I think Sthil quality is definitely going downhill recently. They want to decrease costs and raise prices in the last couple years. Hope they can turn it around and get back on track but they may be headed for a downfall like so many other brands have fallen victim too due to greed.
I have been using anaerobic gasket maker for years. Glad to see someone else using it.
Good video 👏👏
Hi nice work, Stihl have a new mod for the timing cover which has a flow director so the camshft gets better lubrication so maybe they do listen, keep up the great work and share so we can all learn
Jutty
I have the exact unit and have been pleased with it. I will not use a weed eater , the pole saw and blower are used a lot around my place . Roundup and 24d are my substitute for a weed eater. I agree the combi unit don’t match up to the professional line. It does just fine for what I need.
Every time I hear someone say "Click" when not using a torque wrench it reminds me of the Awesome channel Elderly Iron. Another Great channel!
I was thinking the same thing as you were talking about the cam gear I would keep you old cam gear measure the new dimensions and make a sleeve to press fit on to the gear you would have to put the gear in the freezer an heat the brass up no reason it shouldn’t work.
Love the cows just chilling at the brush pile fire 😊 They can be quite curious
Great video as usual. I have the Kombi 94R and learned a lot about how these work. Thanks much for the entertainment and education!
Different engine unit no cam gear or valves
You can point the temp indicator at the wife first thing in the morning to tell how your day is going.
Lol +1!!!
Hi John can i make sum tips . The vales and cam timeing and adjusting must be set by an arrow on flywheel that goes to the last screw on the coil that is for timing and adjusting point.the clutch bushings have seized in the shoe clean and grease. The gasket sealer is not ment for aluminium it is stihl sealer hope this helps. All best Keith
Same issue on kombi 140. Then had pivot from decomp run through cylinder. Replaced with gen 2 140.
Do you run ethanol fuel? I am wondering if that cam gear may not be tolerant of ethanol. I know other manufactures had a lot of issues when the E10 was first introduced. I actually have a Tecumseh ethanol test kit that was a service tool they issued in the 90's to figure out what percentage ethanol was in the fuel of the engines where they were getting premature failure.
Congrats with yet another popcorn-worthy video.
I´m starting to look forward to fridays like when I was a kid waiting for the next episode of my favorite show. (My kids have no idea what I´m talking about of course...)
As i understand you should have had a lot of valve gap at the rocker with worn out cam lobe.
But you had tight clearance,so i think the lack of gap melted the plastic : the constant drag didn't allow a lubrication and caused heat by friction,not the silicone.
You need more frequent valve lash verifications.
For torque specs : check bolt grade,and its thread pitch (imperial,or metric) ,then look for a table sheet with normalized torque specs on internet.
It's normalized,so you can't really make a mistake.
It works for about everything.
Those two pins that the cam wheel and rocker arms ride on are the nemesis of the Stihl 4mix brushcutter engines. The seat of the pin for the cam becomes oval on the engine block and the seat of the pin for the valve rockers become oval on the cover. After that the valve clearance will vary and one will tend to over adjust , this will cause the cam followers to dig into the plastic of the cam. These pin seats need to be repaired with small sleeves. Except for this issue these engines are real jewels and i still have the 100 and 130 engines from more than two decades ago
Handled a brand new stihl at the farmers coop the other day and compared it to my late 80's AV024 and yes the quality has slipped !
Makes perfect sense why it failed I think it got so hot it started making the rtv almost liquid and then the clog happened then the melting of the cam gear
John
I have two engines that will not throttle up. I thought it was carburetor jets but I'm going to look at the valves and if there is minimal movement a worn cam lobe might be the problem.
Thanks David
I must say sir I learned a lot watching that video thank you never even seen the inside of a small engine like that before
Plastic cam, that's disappointing
But cheap!
Unless as he mentioned plastic was used on purpose to make this the sacrificial part. It will fail first before any other part is damaged thus protecting the whole engine. Plus it is easy to replace. Only issue if they are jerks and charge an arm and a leg for the replacement part when they DESIGNED it to break.
@@nostromo526 People just seem to assume that because something is plastic that it was made to be cheap, rather than for some other reason. Same people probably think the shear pins in the collapsible steering shafts should be steel instead of soft plastic :)
*hah, wrote this comment just before the part in the vid* Pretty neat the plastic cam has a built in decompressor it seams, the little metal plate on the back side, and small metal pin protruding from the lobe at one position, whole thing must run centrifugally and deactivate at idle+ speeds... I guess very much a comfort feature, as overcoming the compression isn't too hard, but i guess makes a more 'luxury' product...
Thanks. I've got a few engines of that sort. Always learn something useful.
great job one of the most comprehensive videos ive seen........thankyou
I miss my Weed Eater Model GTI 15T. This was back in the day when things were made a lot better than today's stuff. I had my FS 94 R serviced twice due to carb problem and FS-40 C E with issues.
I half expected you to cut that post with the polesaw.
10 years of service ! no bad I bought a 2 HP chinese made trimmer new and only lasted three months !! 😆😆😆 the guy who was going to fix it told me you are going to spend in parts almost the same you spend for it !! my advice is buy from a well known brand , a machine that will last or give at least 5 years of service is worth every penny !! .
Oil and air mix must be drawn into crankcase and then up into the cylinder through a port and the inlet valve, so very similar to two stroke. This also means pulsing effect of crankcase can be used for the fuel pump in the carb. Cam wear would mean low air flow through engine and low pumping affect for the carb fuel pump. A double whammy. Advantage engine could run at extreme angles as no oil in a sump and four stroke is quieter and more fuel efficient typically than a two stroke. So lower emissions.
Great hands on learning video, thought at the start of the video that i was getting floaters in my eys till i realized it was bugs flying around in front of the camera lol. Was wondering if when you where cutting that monsterous tap root that it jammed up for a few seconds and caused the plastic timing gear to seize for a few seconds, should have had lubrication but it looks like your lobe melted down some. Maybe the valve and push rods got jammed by som we thing and pressure on the cam gear lobe caused it to melt a little. Love your videos keep it up.
The 4 mix do require a bit more maintenance...good oil, good mix, adjusted valve lash. If you don't do those things, the plastic cam gear will burn up. But the 4 mix make great power and with less fumes. I run the fs91, fs111 and fs131. The 131 is a powerful sucker.
great video.I have several Stihl products, my one complaint is you can't find parts online.
This man has no fear, good mechanic/technician.
I love the death metal gardening soundtrack, it adds an element not ordinarily found in trees and shrubs.
Last year i bought a stihl fs90r for 100 dollars from a friend that didn't run and it felt like it had no compression so i got concerned but i took it apart and the cam was worn to hell and the piston is completely fine so after buying a cam gear from stihl and it works great
Awesome now I have something to look at. I have 2 stihl weed eaters that basically do the samething. Thanks for the video
Enjoyable video! Too bad the fuel mix in a four- stroke confuses some folks. I first noticed this when a friend of mine had a new pole saw marked "4-Mix" and I questioned him what that meant. He didn't know the difference between 2 and 4-stroke engines, so the uniqueness of this was lost on him. He was just lucky he got the right fuel - or the dealer helped him out. He actually bought pre-mixed fuel! Anyways, I have a number of 4-stroke model airplane engines that use mixed fuel and use it to lube the bottom end. I think some unburned oil also gets past the rings and helps the lower end that way. I do believe I've seen a passageway from the inlet to the crankcase as you described. I have seen a Troy-Bilt string trimmer that has oil in the crankcase - but it had no carb adjustments beyond idle speed.
That was really good! A lot of work editing so well. Thank you!
I would bet that what you think was rtv is really a rubber one way valve for your primer bulb , there is a really Good channel with great videos on 2 cycle carbs vintage engine repair is the channel . I could have missed seeing it in your first video i guess . The other guy is even better The Repair Specialist .
Perfect repair with awesome explanation.
I've had the weirdest problems with a 4-mix Stihl chainsaw, it would start ok but when trying to accelerate hard, it would kind of choke out and end up stalling. Slowly accelerating up would work okay-ish though and no amount of messing with the setting screws would help. Now it works very nicely and I have no idea why
Thanks for another great video 😁👍👍
This videos are going to be GOLD when all these machines are electric...(like my dad that had a very minute steam engine). Basically all engines are Cuckoo clocks and electric is quartz watch !
I hope that one day you have an comment review and see this comment☺️your video's always come out when its raining where i live and watching your videos always bring a good mood and i can say that i learn something in EVERY video of you
hiya - if you have a 3D printer - you could print a new cam, then use that to make a mould and recast the cam cog part in brass :) Also you could use the lost foam process if you don;t have a 3D printer. UPDATE - I was watching when i said that - so I subsequently heard you saying you'd make a brass copy yourself :)
I design large diesel engines for a living...these little single cylinders amaze me with their use of very simple mechanisms like that compression release. Those cam followers are like toothpicks in my world.
RTV silicone is misused every day by people that shouldn't touch tools. Good job being thorough with everything you do.
27:17 Mmmm, roast beef. *YUM!* 🤤
27:43 Where's the spit? 🤷♂
Thanks for the video Jon. 👍
Always a good day when you learn something new....👌
Stay safe and we'll see you next time.
I think the exact thing you lost is cooling, because by using the gas as coolant in the engine you have a huge cooling power: the hot gas get burnt and exhansted, only cool stuff gets in. But also, when you water cool an engine, you never boil the water, but in your system you can boil the gas, that means that there is extra energy absorbsion by the boiling. it's really regenerative cooling rocket engine territory. thanks for the video, I had a lot of questions when you described the lack of oiling system, and everything got answered later.
Check the hole in the block for the cam gear pin check for sloppy fit mate
The 4 Mix need the valves adjusted or it makes pulling the start rope harder. The also have a plastic cam with a spring for decomp that can go bad
Howdy, (from AUS) love your work, this was one of my fav videos in a while. Love the way you time lapse, we don't need to see every screw turned. My theory, what sort of fuel do you use there in the USA, is there any ethanol involved,? Maybe it affected the plastic?? Also, are you using Sthil synthetic oil? my dealer told me it was far superior. Keep up the good work, one of the better videos on you tube, I am a fan. Cheers Rick
The small plastic cog should have obviously been made out of metal, but for the most part, the parts seem durable and reliable.
did you check the spark arrestor, if its clogged it can bog down the engine, just remove the mesh screen from exhaust and clean using carb cleaner and fine little brush and then blow dry with compressed air and refit. should bring the engine back to life
This sounds like a good thing. It went into "limp home" mode, saving the rest of the motor.
The big end bearing looked bad, for a tiny motor.
Check the mains, as well ?
Limp mode? No... It FAILED.
38:20 You should see the valvetrain in my OS FS-26 Surpass. That engine is only one fourth of a cubic inch in displacement! The pushrods are LITERALLY no thicker than a spaghetti noodle.
You better believe it John man iv been in landscape for years about 30 years iv always had stills.stuf its.not like it was years ago
Nothing is. Wonder who could be behind it all?
I love watching you take s--t apart. It's better than a classroom.
That bottom hose helps make a centuri effect
Just a quick aside. When a friend of mine first saw a pole saw, he named it "Death on a Stick"
Great video Jon
I believe this engine is a 4 stroke which does NOT use use oil from the fuel to lubricate the crank but has a separate oil supply. The fuel for this engine has no oil, I can only assume you lost the oil in the sump ted north