Briggs and Stratton Power Built 12.5 HP Flathead Model 28 Rebuild, Teardown / Reassembly PART 2
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- Опубліковано 6 вер 2024
- PART 2.... In this video i'm doing a teardown and rebuild of a Briggs and Stratton Power Built 12.5 HP Flathead Model 28 Lawn Mower engine. Hope this series helps you, be sure to watch the other parts. And the last part is the first start of this motor after being rebuilt (not a complete break in video, just the first few minutes of running and adjusting carburetor) The only thing i left out was checking the ring gap clearance, which all you do is put a new ring in the cylinder use the piston to push it down about a half inch or so and use a feeler gauge to check the gap on the ring. Use general safety rules when doing anything like this, it is extremely to cut/smash fingers at any point. I cut my thumb really bad on the timing gear on the crankshaft (off camera). Just be careful and use common sense. Thanks for watching
After grinding valves, you can mark with a pencil to tell if valves are fully seated. With a sharp pencil put eight equally spaced marks on the valve seat after having thoroughly cleaned all grinding compound. Rotate with valve tool as if grinding, without lifting valve out of block for 15 or 20 seconds. When all marks are cut thru, the valve is seating properly. This will detect any warped valves which cannot be detected by eye. If a valve leaks, it will obviously cause issues.
I've had a 14hp flathead sitting in my garage for over 3 years waiting for my attention. This part 2 video (and video part 3( was a nice tutorial. Thanks.
usually the crank is pretty clean, but yes, carburetor cleaner on a sychrobalance crank could remove the oil in the bearings, if one needs cleaned i usually just spray wd40 on it then use a rag to wipe it down that works pretty good. great motors! oh wow. never had that happen, you could try vice grips on it, assuming you mean the head is rounded? if the threads are stripped in the rod, things will be alot more complicated!
a basic hone then use standard rings/piston, usually reuse old piston. Then follow one of my newest videos on measuring piston ring gap, then if its to small of gap you will file, and if its to big of a gap you can use .010" rings then file down to spec. Like i said about 90% of the time you can use standard size rings, i'd say almost definetley you can on yours since its more less just starting to smoke. hope that makes sense.
yeah that would work, i've been wanting to get a granite surfacing block, but it costs so much. you can also do it on the head to shave it down to raise compression (for racing engines) thanks for watching!
Brigg has valve guide tools and a reamer tool and a bushing installer. Use a drill ream the guide. Get the bushing tool that fits on the valve. Get next OS rings and file them to correct gaps. Use sandpaper on cylinders. Have a shop to replace the valve seats. Install head bolt inserts. Replace the guides!
depends how bad one is, on internal parts i'll spray them down with carburetor cleaner or brake parts, OR purple power or any degreaser works great too. On the outside i'll use a degreaser, and to make it look good i'll take a wire brush to the crankcase. If you ever work on a engine and the inside of the block and sump have a yellow or golden color to it, thats a coating briggs started using, dont' try to remove it. First one i seen like that i thought oil had burnt in. thanks for watching!!!
thanks! you would use the same type of hone, just be careful as it will remove the metal alot faster than a cast iron sleeved engine! it would be easy to get carried away and remove to much metal. just be sure to use the correct piston and rings in a aluminum bore (chrome rings) thanks for watching!!!
@79firebirdman thanks for the tip, never thought of doing that, makes perfect sense. Always glad to get input like this, thanks again, i will start doing that!
yeah it should loosen up after like a 20-30 minute run or so. If its a push mower you should put the blade on it, they do tend to kick back wihout a blade because the blade acts as a flywheel.
is it just not cranking over, like it turns over once, then pauses then goes again? it could be the starter dragging, i did a video about 2 years ago on rebuilding a briggs starter, if its dragging you might just need new brushes. if this is a OHV motor, it can be something wrong with the camshaft, as they have compression release can wear out, flatheads don't have compression release. try pulling the spark plug out to see if it turns over free then. thanks for watching!!!
2 reasons, it needed rebuilt bad and to make this video for everyone. This motor burnt 3/4 quart of oil in like 20 minutes!!! Thanks for Watching!!!
@V8Mike93 Thanks, The racing engines are a little different, for one they usually do away with the sychro balancer counter weights and dogbone, or they have a billet dogbone or use brass bolt on weights. they also have a racing crankshaft now. and if its above governed speed, they have to have a arc billet flywheel. thanks for watching
Usually I use carburetor cleaner or brake parts cleaner to get most of the grease and oil off the block (inside and out) OR I'll use a degreaser like purple power. Carb cleaner costs more (and not to mention the fumes, and eye protection required), but works faster. Also on the outside i usually go over it with a wire brush to get some oxidation off the aluminum. I recommend some like purple power for the inside and out. Alot of people use a pressure washer, i would if i had one haha thanks...
I hadn't put blade adapter or blade on yet. I just let it idle for about 10 min started it up a couple times. Pretty easy to pull a couple times but really hard to pull most of the time
Hard to say. The low compression would be either the rings, or the valves not sealing properly. to check the rings you have to tear it down, pull the rod and piston, then remove the rings from the piston and then follow a recent video i did on measuring piston ring gap, go through my videos, its a fairly recent video i did. I wouldn't think the crank is bent. It should crank over really good with that little compression.
it usually doesn't take to much, just make sure you run your drill at a fairly low speed and go up and down at a moderate speed, to slow moving will make horizontal scores, to fast will make the crosshatch to stretched out, if you a very very slight scores (if you can't feel them with your finger nail) then you can hone them out usually, if you can feel scores it would be best to have it bored then use oversize rings/piston. GENERALLY speaking on a engine's first rebuild you can get by with>>>
glad you got the bolt out ok! when you replace the bolt be sure to get a grade 5 or grade 8, if you don't get a briggs replacement. Ohh. I've never done that my self, it requies a special (non cheap!) tool to remove it, now if its not to bad they can be ground, but that may require a over size valve which you don't usually see for small engines, you will probably have to take it to a shop (machine should be able to do it, if not a SE shop can) and get a new seat pressed in.
@1899lpv well the problem with doing that would be: even if its just a few revolutions before the oil start circulating the cylinder/piston can start scoring because metal against metal is no good. While it may not do to much damage, any scoring before its broke in can cause the rings to not seat or wear prematurely. I always use STP, you can use regular motor oil if you want. Just don't use grease.
haha i hear ya, well i'm glad to help out, anytime! Thanks for Watching!!!
@1899lpv it would take a while to get the oil coated all over the piston and rings. STP is just a good insurance that everything is lubricated when it first starts up. even if a engine has been sitting for a log time its best to pour a little oil in the cylinders and let it set for a while. hope this makes sense. oh by the way the final part will be up tomarrow! thanks for watching!
no problem! always glad to help out!
@1972FordF150 yes and no. They have to be drilled out then reamed to exact size, then the new ones pressed in. If you had a press and a milling machine you could do it at home. i really enjoy rebuilding these motors, i can't wait to build a racing engine, it costs so much to do it right. thanks for watching
@V8Mike93 i'm gonna do it sometime! put the 28 crank in it and a good cam and flywheel. i thought that was you haha i'm gonna post links on heymow as soon as i get all parts up. It takes so long to edit these HD videos, and i'm just using the youtube editor haha i hope to get part 3 up today, but it just depends. And it shouldn't be anymore than 4 parts
@jajaid6 yes they can be adjusted but its alot harder. On these if you have to much valve lash, either reseat the valves so they drop down further, or you can weld the stems then grind to what you need, now if the valve lash is to tight, or like on this engine, there was no clearance, then grind some off the stem till you get the correct gap. Thats the only thing i like about OHV engines haha thanks for watching.
head is 185 IN. Pounds, so that would be about 15.5 FT Pounds, oil sump is one of 2 different torques, if the bolts have a separate washer then its 140 IN Ibs or about 11.5 FT pounds if there is no washer but has a washer built in on the bolt then its 200 IN Pound or about 16.5FT pounds. hope this helps. Thanks for watching!!!
@PGXI thanks. haha the rest of the parts will be up ASAP.
I know that it could sound stupid but, could you crank the motor with the spark plug disconnected so all the parts gets a good coating of lubricant OR its preferable to coat all internal parts with STP oil treatment while putting the motor back together?
i figured that just wanted to be sure haha yeah i'd say vice grips would probably be about the only option, don't have room to use a screw extractor.
You are a wealth of knowledge ! thankyou for sharing ,these vids are very helpful.
Benjamin Egan I don't know about all that, but I appreciate that! Your welcome, always glad to help out! Thanks for Watching!!!
no problem, glad you got it figured out!
can these valves be adjusted like the ohv's?whats the best place to start trouble shooting these flatheads that start hard and have poor compression?
have you tried it since it ran? they usually loosen up after running for a little while. Be sure to change oil soon, like after a hour of running. There will be a little metal in it, its perfectly normal. If it looks like metallic paint then there is something wrong though haha
No i never have, i usually use wd40 or any type of thin oil like that. brake fluid would probably work alright though i would think, or auto transmission fluid too. I usually use any degreaser like purple power for carbon clean up carburetor cleaner dissolves it fairly well, a small wire brush helps alot with it. For carbon like on top of a piston or head, i'll use a wire brush on a drill to clean it up (with piston all the way up). thanks for watching!!!
i'm pretty sure the smaller one should work fine, the big one sounds to big. i bought a pack of 2 at harbor freight, not sure of the sizes, that sounds about the same as mine, i'd go with the smaller one. i've never used the bigger one in my set, its mainly for big car engines. hope this helps, thanks for watching!!!
I was go to adjust exhurst valve at tdc because its closed and move down a 1/4 to adjust the intake because its closed
that is fine to do, its actually recommended, i just got in the habit of tdc.
That you, going to the shop
sounds like the valves need reseating (lapping) it may be also be running to rich that will cause that. Is it misting or pouring out? if its misting its the valves or running to rich, if its pouring out sounds like a problem with the float/needle valve. thanks for watching!!!
Good ol flat file with stone.
Thanks for Watching!!!
when you say yanking your arm off do you mean it was just hard to crank over or did it kick back and pull you back into it? If it was just hard to crank, thats common on a rebuilt a engine, on a rebuilt car engine you usually have to have 2 batteries hooked up to get more amperage to kick it over. This engine in this video that i rebuilt was pretty stiff. If it was kicking back and pulling the rope back, thats usually in the timing. hope this helps
no problem!
thanks, your welcome!!!
homemade fix to not owning a milling machine, to resurface the top of your cylinder, tape a big peice of fine grit sandpaper to a table and gently slide the top of your engine across it.
Put blade on and now mower pulls over easy thanks man
Ok how long do you have to hone the cylinder wall? and where did you buy your honer at? After honing it can you use the standard rings or do you have to use over sized ones?
Hello sir! I have gotten around to doing this rebuild, but found out my intake valve has a pretty large gap. Light seeps through a lot, on one side, don't think I can grind down that much. Cant see if valve is straight, it might be slightly bent? Cant figure out if I should order a new valve, or if the problem is in the valve seat. Any ideas? Thanks!
piston tdc and 1/4 down to set the valve guage on a 12hp briggs straton
Yep, that works, i usually do tdc but thats what is recommended. Thanks for Watching!!!
What do you clean your engine with during a rebuild The crank and all
Will degreaser or carb cleaner not hurt anything in crank?? Same engine first flathead That I'm rebuilding. I got one screw off piston rod the other is stripped. Any suggestions?
What did you use to clean the block up. Anything for a little carbon buildup in exsaust port
Thank you
Hey man I took the intake valve out of flathead and the valve seal was damaged any idea how to remove it By the way I finally got that stripped bolt off rod
Thanks
You are the man. You helped me out a great deal. Thanks brother.
@fnaguitarplayer9 Hmmm I have an idea for these valve guides : step 1 get drill bit and drill it out. Step 2 get new valve guide. Step 3, get big hammer. Step 4, WHACK on the top of the guide and it's in. LOL yeah I'd like to build a racing engine then throw it on something haha. But I'll probably never get to that because I'm so damn broke.
Good series. I'm at this point in a rebuild and I would like to hone the cylinder prior to installing new rings. I'm wondering if you have ever honed an aluminum cylinder Briggs and what equipment you used.
Love the valve lapping info.
thanks! appreciate that!
what do you use to clean the inside of the block and cylinder? and what do you use to clean the outside?
im just curious as to why you took this thing apart??
Have you ever used brake fluid when you hone a cylinder?
good video !...... i missed part 1....Dam it
@1972FordF150 yeah definitely
I rebuilt 5 hp briggs runs good after yanking my arm off any ideas why it's hard to pull over?
thanks for watching!!!
What was the ft lbs of torque on the oil sump and the head gasket?
Is there a way to put new valve guides in at home ? cool video dude I wish I had crap to do around here like this haha
@V8Mike93 ohh sorry lol i'm on there to. I'm guitarplayer on there. i heard that, it costs a ton. i hope to eventually start machining all my own parts. you might find another one of my videos interesting, its called "Briggs and Stratton 11 Horsepower vs 12 Horsepower / Briggs Stroker (Mainly Plans)" alot of people hate the model 25, i think it has great potential myself!
See if a disc brake bleeder screw wrench will loosen the rod bolts.
The one i got is 5/16" and 3/8" the bolts are 1/2" Thanks for Watching!!!
Ok thanks this will be very helpful!
Thank you for your videos . I have a 8 hp Briggs that the walls of the cylinder are scratched ,I can feel it with my finger .
Do you think is wort it fix it or get a new one .
There is no compression .
I'll appreciate any response thank you
+Harly Farfan Your welcome! If it has a cast iron sleeve you should be able to get it bored out, if its aluminum bore then theres not much that can be done, honing usually won't take out real deep scratches, if it does then the cylinder usually becomes egg shaped. And with aluminum cylinders you have to use chrome rings and a chrome plated piston, which is only available in standard size, so the only other option is to have it bored and a sleeved pressed in which is doable but will cost quite a bit. Hope this helps some, Thanks for Watching!!!
Where did you find the rings at? I can't find them anywhere.
How did you clean all the sludge out of the case? Gasoline?
+cavarlyvet I usually use carb cleaner or i also found that penetrating works even better, I use the walmart brand supertech penetrating oil and carb cleaner, works great. A pressure washer will work even better but it will spray back at you as well. Purple works too, but not as good as the others. Gas is a good cleaner but is messier and dangerous. Thanks for Watching!!!
Just hard to pull over. Not pulling the rope back.
and remember they don't make oversize chrome rings
sorry did not catch what you were doin with that drill in cylinder can you explain please
+tigertruckerman I didn't go into to much detail on the video, I will next time I rebuild one, but its called honing or "deglazing" the cylinder, what it does is puts a cross hatch pattern into the cylinder walls, looks like a # in a way, just at a steeper angle, what happens is after its done and the new rings are installed, it basically acts like sand paper to seat the rings to the cylinder, it smooths out slight imperfections and makes a really good seal. I don't have any videos on it right now, but there is alot on youtube and alot to read online about it. But you want to run the drill slower than what i did in the video and move it up and down faster too, this puts a really good pattern on the walls, and it usually doesn't take to long and you'll want to use wd40 or some other light oil on the walls and stones. Hope this helps explain it better. Thanks for Watching!!!
purple guy. Use sandpaper and not hone cylinders!
What type of grease were you using, STP what specifically?
STP oil treatment, in a blue bottle. You can also use lucas heavy duty oil stabilizer, its easier to work with since the bottle has a spout built in. Just plain motor oil works good to. Thanks for Watching!!!
@@fnaguitarplayer9 thanks sir. As I watched more of your videos I found you stated it in several others. Appreciate the work you put into all these videos.
@@ncameron7 Your welcome!
What is the model number of the motor? I have the exact same one but I don't have the original cover, therefore I don't have the model number. I am looking for the piston rings. Thanks!
BADASSF250 If i remember correctly is a 281707 As long as its a 28 any ring set should work (should), the only real difference is the oil ring type. But you never know if they made them with thinner or thicker rings. Thanks for Watching!!!
How how do I adjust carburetor idle screw and air mixture screw machine runs on low idle just fine and runs on choke just fine but when I put it to the running position on high it wants to backfire and misfire how do I just screws on carburetor and also governor I cleaned carburetor throughly I'm not sure how to fix thank you
Nick Chaix I actually have a video (a very in depth video) on adjusting these carburetors (one piece), its running to lean, the screws should be turned out, but refer to this video here on adjusting and fine tuning: ua-cam.com/video/TlSAOkQnI1g/v-deo.html and for governor adjustment, follow this video: ua-cam.com/video/9rO8AvDrdeM/v-deo.html thats the best way I can explain it to you, if you have any questions feel free to ask me. And if its a newer style with the 2 piece carburetor, there is only one mixture screw, just turn it out it about a turn and tune. With the newer 2 piece carburetors they usually have to be rebuilt (carburetor kit) since there isn't much adjustment. Thanks for Watching!!!
Nick Chaix Maybe replace the governer springs. Check the carburetor. Check for vacuum leaks at the intake.
I have a 12.5hp Briggs and Stratton motor and it smoke's a lot when I start it in the morning to cut grass is it the piston rings are the Head g when the motor get warm it stops smoking please please help me
Its probably either the rings are starting to wear and/or the valve guides are worn.. Thanks for Watching!!!
Thank you so much
I sure I will have more questions about this motor
By the way your videos are very helpful
Threads are fine just head of bolt
Im working on a 12hp briggs from 1987
I hear ya, great motors! Thanks for Watching!!!
@1972FordF150 haha if it were only that simple lol it would have to be at least drilled out on a good drill press, a milling machine would be the best method. haha yeah its pretty expensive
Thanks man yours always helpful
@V8Mike93 alrighty well guess i'll talk to you on part 3 haha
I have a Model 28A707-0122-02 engine, and I have a question for you about the crankshaft. Th rod threw in it, but it did not damage anything. The crank does have score marks on it, though. Could I get it polished out or do I need a new crank?
As long as the scratches aren't to deep (like your fingernail won't hang on them) then you should be able to polish it up, using a emry cloth or something along that line. Those are great engines, hope you get her going again! Thanks for Watching!!!
Alright, thanks! I think my fingernail can get hung in it, so I guess I need another one.
I'd try polishing it first just to see if it smoothes out, cranks are high dollar. I put one together that some scuffs and never had any problems with it. Just when you get the new rod, check for play on it. Now you can get a .020" undersize rod and take the crankshaft to a machine shop and have it turned down, that could save you a ton of money doing that. Alot of people do that.
Okay, thank you!! I will try to get it machined, seeing that it got too hot when I put it back together the first time.
Also, when I get it machined, should I get it .020" undersized compared to the stock journal measurement that is on the Briggs and Stratton spec sheet?
where did you order these rings i can't find em lol
I ordered them from tulsa engine warehouse, you can also find them on ebay and just about any other small engine / lawn mower parts stores. Thanks for Watching!!!
just put lock washers on you rod cap bolts
That would work too. Thanks for Watching!!!
Exhaust
@fnaguitarplayer9 Yeah it would be expensive. But I'd rather do that then buy a new engine haha
Just felt stiff
AND THEN OVERDRIVING THE AUDIO ON THE VALVE SHOW.. PLEASE
Sorry, that camera I used almost 10 years didn't have a limiter on it, and i was using youtube to edit videos at that time. thanks for watching!!!
It is a brigs ans stratton 12.5 hp. I/c
WOFE ALIV AND HAPPI AT HOM. DON REPORT.
Stop eating your nails young man
no problem!
no problem!