Moves air for a living, sits in an igloo for you tube. Thank you for your videos. You have no idea how much good you're doing by explaining this to the average guy watching you tube. I can't wait to crack open my gp460 scooter engine and play around in there
Got an interesting video for ya.. How to port a saw WITHOUT changing timing numbers. Just a recap on flowing, widening, shaping, etc etc. Might be a less intimidating prospect for people and get some people to jump in. I certainly have "numbers anxiety" when a lot of saws could really benefit from the basics and some TLC
One thing people lose sight of is how much energy is in a moving stream of air. Ports may open, close, whatever, but that doesn’t mean air has stopped moving somewhere else in the system. There’s a bunch of inertia available for use. 😎
Absolutely. On a high rpm saw, I think a wider intake port at the cylinder wall gives the incoming charge a place to compress so the carb can keep flowing.
@@ikesquirrel yes- pressure recovery. Convert velocity to pressure that is available for use when the piston uncovers the port. All it takes is correct port area ratios.
After I got an introduction to Kensie over at Bayou Country PowerSaw’s when Buckin was getting Harvey after the first Buckin Stock to talk numbers and the TinBasher here was getting going with Jeremy Bell and Kensie was starting the UA-cam thing too Harvey started talking about a port mapping… and Kensie went ahead and made a porting sheet that you could three hole punch and add to your binder as you had added saw’s that you were porting… there’s a little dwell time between the various functions of your stages on your two stroke… when you can actually see those little rest periods between those stages you can actually see the entire process of your engine and make everything match and balance much more easily for me… I’ve absolutely got to see everything all laid out on paper in front of me… if your rest period’s aren’t equal then you’re not getting the most power or the most efficient stroke… it’s all about each stroke in my mind… and the combination of those 13,000 stroke’s…
On my motorized bicycle two stroke..at "high" rpms..the air/fuel/oil mixture wants to return back to the intake, having a reed valve would help this but if we had larger crank volume, it would be more beneficial.. everyone wants to stuff their crankcase and I believe this might create better suction but if you don't have enough a/f mixture in the crankcase, it's going to starve for fuel.. possibly making for a lean condition..or cause misfire, over heating of bearings cause of lack of oil..etc etc etc..
Yeah what those guys said! Good vid, good theory/explanation. However as some other commentors have pointed out, the primary expansion cone of the pipe aids exhaust evacuation and creates a negative pressure wave behind it. This negative wave will actually bring the cylinder into a negative pressure state helping bring the new charge into the cylinder arguably as much or more than the pressure in the crankcase alone. You need a proper pipe with proper tuned length so the refraction wave can scavenge as much of the charge back into the cylinder. Similarly to 4 strokes with their valve overlap you have to account for airflow velocity. I feel like it's easier to think of it as liquid (fluid dynamics) circulating inside your engine. Just because the piston changes direction doesn't immediately affect the flow. The velocity will continue flowing while slowing for (X) number of degrees based on (x) rpm and port shape (length x diameter)... I just like thinking liquid because unlike air you can see it continuing to move after the glass or bucket has stopped... When the piston closes of the intake the charge in the carb continues to pile up behind it exactly causing a refraction wave to flow back through your carb. Now you have single double and triple cardboard air waiting for your piston to suck it in. Jeebus! I'm going to stop now, my head is starting to spin. Oh, and mean squish velocity will possibly have as big of or a bigger effect on your power characteristics.
This cut away series is fantastic! Two strokes are so simple they confuse the heck out of me. I get 4 stroke car engines they make sense to me. These little things I couldn't get you have explained so much. Thank you.
The exhaust pulse after the power stroke does more to pull the intake charges into the chamber more than many believe. The pressure differences between the two is multiplied by more efficient pipes. Thats why they work
This is an excellent video Tinman, thank you, home sick and we just had 60 cm dumped on us in Marathon Ontario...I think this storm missed you...anyways thank you for the content👍💪✊
Started reading about 2stroke theory back in the 60s, it’s complicated. Rode 2stroke motorcycles in the early 70s- porting and pipe making a world of difference in how they ride.
That's a helpful video keep them coming I've been getting parts to attempt my first 372 build you and Harvey are great inspiration seeing your videos is what made me to decide to try porting and playing with pipes made one of Harvey's for it my goodness its loud and narly but definitely made a big difference
Thank you for sharing your knowledge and tips with us! For years I've been right at home inside of 4 cycle automotive engines. (GM small block, big block, 3.8, Ls. Ford 2.3, Cleveland and Windsor. Honda F/H, B and K series. Likely more I'm not thinking of) bikes, ATC's, quads, lawn equipment etc... but 2 strokes and their theory were a foreign and honestly intimidating thing to me. I've done a few 2t ATC/bike top ends but didn't even dream of modifying any 2t engine. NOPE! Lol. Thanks to you and your wonderful explanations, 2t engines make perfect sense to me now! You were the person to open my eyes to the world of chainsaw porters/builders on YT! I'm still very green but learning and have no second thoughts about "cleaning up" or tweaking port shapes in saws. Haven't gone far yet but have seen very noticeable gains on a few saws so far! Long winded, late night thank you!!
Very good info. One thing I have learned is port velocity and exhaust scavenging. When the exhaust is pulling the gasses out due to velocity, you actually suck fuel and air out of the transfers, which creates more velocity in the transfers and crankcase. So exhaust has a ton of importance to allowing the pump to actually flow. Just a little thought to keep in mind when you look at blow down and intake port vacuum.
@@asphaltcowboy7868 that all depends on the design of the cylinder. If you impede flow by reversing the flow, it's possible to get a reveres flow/swirl affect. That would most likely inhibit velocity in many areas. The more you get out, the more you get in, and at a given rate of time and speed, the more power you can create. It's all a balancing act.
There's many of us that move a lot of air both low and high velocity and we'r not in the HVAC game lol! Thank's for sharing some of the inner working's of the two stroke world with us Tinman take care.
I like the thought on the intake timing with vacuum or amount of negative pressure it creates but you're still increasing volume in the case from bottom to top thinking about it and on the way down if you have reeds like in a snowmobile it should compress all the air till the intake closes then all in the case till the transfers open. I do get the initial high energy pull to get the air moving with the extra vacuum as the intake cracks and how that would help with response or acceleration. I ported a 562 3 or 4 times plus opened exhaust, opening it up the ports more and more and ran it next to another modded 562 that had a decked jug and cut "pop-up" and modified muffler piston and they were toe and toe but I went as far as case porting when I had to weld up the bar oil tank. I'm currently looking at an air cooled yamaha sled and how I could get some extra power out of it with porting
Great video. I have recently built a 372 big bore using information gained from your channel and the Ironhorse. The finished saw starts good, idles great and is a very strong work saw. I have made a couple of pipes for this saw and the one that seems to work the best so far is fashioned very similar to the pipe you built for Hogan's 266. As you say all the time, it's about moving air!
Hey tin man watch all of your shows. You are an incredible guy with a chainsaw and fixing it. I wish I was half as good as you. You are an awesome mentor and a good person to watch on the tube. Awesome, thank you for your time and your patience sincerely woodcutter. Anthony Washington State. If you ever come up here, come on up Washington and got some nice big trees and some big sauce. If you wanna try some. I like your opinion on a lot of Chainsaws and stuff
13:05 to answer your question. Gas mass velocity and reflected impulse energy. The exhaust pulse and the energy release from the cylinder that both travel at different speeds cause a vacuum to exist in the cylinder. This cylinder vacuum through the transfer ports preconditions the lower chamber to additionally draw inlet vaccum on the subsequent cycle. As the cycle speeds up the mass column on exhaust and inlet become more significant till the rebounding pulse energy is overcome by restriction, phasing and frictional losses. So it's not just an air pump it's also tuning energy gradients.
On small piston port engines I found the best way to experiment with intake timing was to grind that side of the piston skirt 0.5mm at a time until its gone too far then go back one step. Altering the cylinder port is actually better because it also increases area. Pistons are cheaper than cinders tho lol
Very interesting to consider, I like a nice responsive nice idling saw for climbing. It's nice to have a screamer but if it's slow to respond or idles poor it's hard to use. Almost done my last 346xpg with close to stock timing, lightened and polished piston and freed up exhaust.
Cool video about Long and short blowdown . If you run short blowdown less time to compress so then you can't open your lower transfers as much because there is not as vacuum or case compression. But if you run longer blowdown it has more time to compress so you can grind more on your transfers. I guess it is like a combustion chamber the smaller you get more compression the bigger the less compression.
I love your videos and I'd love to see you do something on motorized bicycles just cause the torque aspects a little bit different it'll be something new for you to learn and you know enough to teach us about it
I simplly don't know about the engineering part of it, my intention is just to repair them not to modify them nor build one; but it is interesting listening and seeing how the 2-stroke operates.
Thanks for the ❤ on my earlier comment ( grinding piston skirt ) pardon my ignorance I'm a motorcycle guy and 2 stroke but I know very little about saws, what are the ideal power characteristics? I doubt if midrange is as important as on a vehicle and I'm guessing a long over rev past peak power rpm so rev the thing to oblivion then start the cut and when the load comes on and rpm is dropping the torque increases?
If you ask 10 saw builders "what's the ideal...." you'll get 10 different answers. I like quick reving and lots of power up top where the saw spends life.
2-stroke MX bikes are all full circle cranks for tight primary compression, which helps the reed valve open earlier. It does not matter what track they run on in that respect. That may not have been true in 1971, when the Jennings and Bell books were written, but they are all full circle cranks today. The father of the modern 2-stroke may be Dr. Gordon Blair, but I have not read much of his stuff.
From what I understand, "blow down time" is about the cylinder "blowing down in pressure" to zero pressure, before the transfers open so there is no pressure left to resist the transfer flow into the cylinder on the down stroke, at the rpm's you are running at. Personally, I don't adjust blow down time at the transfer port roof, but there may be some power there.
Hi Tinman! Great fan of your videos!! Greetings from Athens Greece 😊 I got a Husky 50 - open transfers . It would be great to make a video dedicated to open transfers porting , tuning etc! Thank you very much 😊
Changing transfer or port timing is similar to changing a camshaft in a 4 stroke engine……you may lose suction or vacuum just like adding more duration in a camshaft for a 4 stroke….loss of low end but will gain top end power….adding compression will help compensate…granted that may be hard to do on a chain saw …
Re : expansion chambers. I’m under the impression that the expansion chamber on a 2 stroke acts as a higher pressure space (than atmospheric) after the combustion chamber that aids in pushing exhaust gases backwards into the cylinder. In order to optimise power and response, the shape and size of the expansion chamber is tuned to help aid this process. If this is correct then back pressure plays a major part in the efficient running of a 2 stroke. Is this correct.
I am not a 550 expert (I am a 488 guy), BUT....That Polaris 550 is a Piston Port with a reed that controls that extra intake to case port. On the Polaris 488 Twin and the very closely related 244 single Polaris ATV engine...The ATV and the Utility Snowmobile engines run a Longer Piston Skirt (Shorter intake duration)....To make better low end torque, more case vacuum (Powerband is around 6000)....VS...The Trail Sleds run a Shorter Skirt (Makes Longer intake timing - along with other porting stuff) to push the Powerband closer to 7200... The Liquid Cooled 488 (aka 500) uses the same piston as the Fan Trail 488 Engine but has hotter porting timing, pushing max power to 8000 (and of course more compression/No Big Fan to spin) - I have had better luck with 488s than 550s - Just my experience.
Great video.... Now I've got a question. So you said if you increase the rpm 5000 then the cooling fan spins 5000 more rpms as well. Totally agree with this . Now honest question time. On a boat, you spin any prop to fast and you get cavitation. Can this happen with a cooling fan on a saw? I don't know I'm not a rocket surgeon at all just wondering if there's a crossover. What do you think?
Well Air and Liquid in theory are both a "Fluid" and YES...An Aircraft Prop is more efficient at lower RPM than at higher RPM and on some engines you can push the tip speed faster than the speed of sound...which makes a snap that is kind of (to my knowledge) a form of cavitation!
ylösvirtauskanavien purkaus aukot pitää olla aina mahdollisimman matalat mutta riittävän leveät. Virtausnopeuden takia ja myös tuon kampikammion paineen takia. Mutta toki pakoputken pulssit sotkee ajatustani ja sitä mikä on todellinen tilanne eri vaiheissa. itse olen pilannut yhden sylinterin liian korkeilla ylösvirtauskanavien purkausaukoilla. Jonkun pitäisi rakentaa sylinteri jossa on läppäventtiilit myös ylösvirtauskanavissa. Ja testata miten se vaikuttaa.
I think you just solved my idle problem with my 066. I accidentally lowered the intake timing and I can't get it to idle down enough for the chain to not move
That may be you issue. Too much intake timing will.cause the saw to be rich at idle sp it will need to idle faster then stock or it will often choke itself out.
What i have learned is many people cant widen and polish ports but very few people actually understand what everything is actually doing in a two stroke.
I am of the mindset that long blow down 28-30* reduces torque but allows higher peak rpm. I also feel that if transfers are raised, intake floor should be raised the same amount to maintain Crank case compression, it is very important, 40 degrees of crank rotation is how long case compression should occur. If you want a piss revver with no real power, lower the intake floor. Also, the much touted dual port muffler reduces cylinder pressure sooner, therby Effectively raising transfer ports and allowing transfer flow to begin sooner. Me likes powersaws….! Also, Setting squish @ .020” and adding dual port muffler and a free flowing airfilter is a damn good, reliable setup with minimal effort.
I'm currently working on a motorized bicycle engine.. not saying I wouldn't or won't..cause my bike is already running really good, but just out of being curious.. what do you think about swapping out a dome piston to a flat-top piston? Of course the bottom of cylinder would have to be resurfaced to make up for the quench gap..but wouldn't in logical terms a flat top Piston mean less blow-down and more down force on the piston it's self??? The pro when it comes to dome is a tighter quench gap (more compression) but the con is..the down force is directed over the piston and into the rings..
😂😂😂👍. “ not just with my yapper!!!” LMFFAO!!! How freaking funny is that!!! Dude…I absolutely love the laughing while learning together kinda mojo that makes you… you! Love your style of let’s learn about this together… 😂👍💪😉
Mr Tinman......question about unlimited coils for the 372. what are the gains, losses or downside of going that rout as opposed to full porting a work saw? thanks.....Jim
Hi Mr Tinman, I look at all your educating videos with lot of gratefulnes, thanks! Could this sucksion area be told in degree’s, and be related to lower transfer area and volume?
Wont air volume and pressure differences influence that suction too? If you raise the port on top, and flow the bottom but opening it at the same time, that will increase air volume in the case, which will slow down air movement. So although you have better "flow", you also lose air velocity. Or am i wrong?
If you open the intake timings too much, or if you widen the lower transfer ports too much, you generally get a rather slow saw. A lot is not always the best.
Man I have a Echo 670 and I don’t ever remember a saw that has that kind of compression it’s they only saw that I put my foot in Handel to start and I can pull it free hand but it’s safer to put you foot .
When my bb 372xp is at bdc, are my upper transfers supposed to or better if completely open like uncle harve did his piston, I got big squish and my bdc kinda covers the transfers, file piston to taper to the transfer? Talk to me tinman!
I've always liked staged blowdown with quad transfers, keep up the great videos... Does static pressure count in 2 strokes? Lol. I'm a sheet metal journeyman in Alberta.. But went the custom route
I'm new at this what about a Stihl 034 AV ,planning mild port work and some exhaust polish finishing.but I got a question.What would an expansion chamber pipe? How does resonance work on a chain saw...versus motorcycle
With as successfully as this channel is and you knowledge have you ever though of checking out the 2 stroke bicycle kits there 38 to 40 mm stroke you may can make a beast running a ms660 head and piston
Let's talk hard truths bumping the compresion is really fuel dependent you could go way high and run e85 and even with stock port timing see a 10% bump in power with not alot more usage of fuel because of the increase in efficiency all while the saw is actually cooler running. Now porting probably gets you 10-15% over stock but you are always trading peak power for losses in idle/ starting and fuel use the higher you push but a good pipe has shown to be good for 50-60% more power just bolt on and go with a carb adjustment
I have always wondered why blowdown is important because I cant see what the point is. However time from intake closing to transfers opening is something I consider much more important. I just built my husky 444 acording to the jennigs method and with the yamaha numbers jennigs talks about. I have to run it in bigger wood before I can say if I succeeded or not
I could watch this video 100 times, great information. Just watched Harvey running his stock 372, check it out. TC Mahalo Tinman 🤙🤙🤙 Does anyone know where to get a recoil cord pully for a 44 husqvarna? Or the whole recoil?
Lowering your intake increase the time in which air can enter the crank. So why doesn't it increase suction? A higher intake means that the crankcase only has time to be filled at very short time when the piston is at the top
@@tinmanssaws The intake suction continues to TDC. But it is flowing as soon as the skirt opens the port on a piston port engine. The reason why a lot of intake duration will hurt lower rpm's is because at those rpm's, with a slower intake velocity, the pressure of the cases on the down stroke starts blowing back into the intake before the port is closed. But with higher rpm and air velocities into the intake, it can help a higher rpm engine sing with more time to fill the cases.
The bikes have gears so can have a very narrow powerband, I'd imagine a saw needs a bit more torque, I know next to nothing about them tho, I'm basing this comment on single speed kart or scooter engines.
Crankcase pressure and volume is very important,and yes imtake timing and uppers timing can effect it ,tell me why the hell do you hog your lowers so much, increasing the volume so much, obviously haven't tested that theory
Actually at high revs the magnetic issue "cogging" negates itself and the ignition timing can take advantage of this with the right coil, spark advance can be induced. The flywheel fins don't create much drag after a certain speed either, as they are a very crude centrifugal fan concept and the air stalls. This is also why he is over confident with it being adequate for a "hot saw" ( performance modified).
more power more energy more heat ,,,, if you tune for power you need to use water cooling or minimum larger head finnage and bigger fan pass more air.@@mrgoodman6620
![2 Stroke Tips & Tricks [Blowdown]](http://i.ytimg.com/vi/0-DJP04BLRg/mqdefault.jpg)
Moves air for a living, sits in an igloo for you tube. Thank you for your videos. You have no idea how much good you're doing by explaining this to the average guy watching you tube.
I can't wait to crack open my gp460 scooter engine and play around in there
Thankyou for being here
Got an interesting video for ya..
How to port a saw WITHOUT changing timing numbers. Just a recap on flowing, widening, shaping, etc etc. Might be a less intimidating prospect for people and get some people to jump in. I certainly have "numbers anxiety" when a lot of saws could really benefit from the basics and some TLC
I highly recommend reading Two Stroke Performance Tuning by A. Graham Bell. ~Its a fantastic book with tons of useful info and advice. Cool vid!
One thing people lose sight of is how much energy is in a moving stream of air. Ports may open, close, whatever, but that doesn’t mean air has stopped moving somewhere else in the system. There’s a bunch of inertia available for use. 😎
Absolutely. On a high rpm saw, I think a wider intake port at the cylinder wall gives the incoming charge a place to compress so the carb can keep flowing.
@@ikesquirrel yes- pressure recovery. Convert velocity to pressure that is available for use when the piston uncovers the port. All it takes is correct port area ratios.
After I got an introduction to Kensie over at Bayou Country PowerSaw’s when Buckin was getting Harvey after the first Buckin Stock to talk numbers and the TinBasher here was getting going with Jeremy Bell and Kensie was starting the UA-cam thing too Harvey started talking about a port mapping… and Kensie went ahead and made a porting sheet that you could three hole punch and add to your binder as you had added saw’s that you were porting… there’s a little dwell time between the various functions of your stages on your two stroke… when you can actually see those little rest periods between those stages you can actually see the entire process of your engine and make everything match and balance much more easily for me… I’ve absolutely got to see everything all laid out on paper in front of me… if your rest period’s aren’t equal then you’re not getting the most power or the most efficient stroke… it’s all about each stroke in my mind… and the combination of those 13,000 stroke’s…
On my motorized bicycle two stroke..at "high" rpms..the air/fuel/oil mixture wants to return back to the intake, having a reed valve would help this but if we had larger crank volume, it would be more beneficial.. everyone wants to stuff their crankcase and I believe this might create better suction but if you don't have enough a/f mixture in the crankcase, it's going to starve for fuel.. possibly making for a lean condition..or cause misfire, over heating of bearings cause of lack of oil..etc etc etc..
What about open transfers?
Yeah what those guys said! Good vid, good theory/explanation. However as some other commentors have pointed out, the primary expansion cone of the pipe aids exhaust evacuation and creates a negative pressure wave behind it. This negative wave will actually bring the cylinder into a negative pressure state helping bring the new charge into the cylinder arguably as much or more than the pressure in the crankcase alone. You need a proper pipe with proper tuned length so the refraction wave can scavenge as much of the charge back into the cylinder. Similarly to 4 strokes with their valve overlap you have to account for airflow velocity. I feel like it's easier to think of it as liquid (fluid dynamics) circulating inside your engine. Just because the piston changes direction doesn't immediately affect the flow. The velocity will continue flowing while slowing for (X) number of degrees based on (x) rpm and port shape (length x diameter)... I just like thinking liquid because unlike air you can see it continuing to move after the glass or bucket has stopped... When the piston closes of the intake the charge in the carb continues to pile up behind it exactly causing a refraction wave to flow back through your carb. Now you have single double and triple cardboard air waiting for your piston to suck it in. Jeebus! I'm going to stop now, my head is starting to spin. Oh, and mean squish velocity will possibly have as big of or a bigger effect on your power characteristics.
I don’t know much about saws but it’s great to watch your excitement ! Scott
Nice work on the nuts-and-bolts of the way a two-stroke works. 👍👍👍
This cut away series is fantastic! Two strokes are so simple they confuse the heck out of me. I get 4 stroke car engines they make sense to me. These little things I couldn't get you have explained so much. Thank you.
Great video! The cutaway is the icing on the cake!
Great video Tinman and you're right that 372 that Harvey did really runs great. Check out the video
The exhaust pulse after the power stroke does more to pull the intake charges into the chamber more than many believe. The pressure differences between the two is multiplied by more efficient pipes. Thats why they work
This is Good stuff ,if your new to 2 strokes ,this is worth its weight in gold!
Man you packed a ton in this one! As Walt once said, "I'll let you ponder on that." Great vid man 👍🏻
Think I just watched this three times and still a lot of good information keeps hitting my brain..lol..
Thanks!!
This is an excellent video Tinman, thank you, home sick and we just had 60 cm dumped on us in Marathon Ontario...I think this storm missed you...anyways thank you for the content👍💪✊
Nice Theory 😊
Fantastic video Tinman.
This is the info i crave, the more you know the better the decisions you can make.
Time for a second watch.
Tinman your content always seems to mirror the build I’m working on, crazy!
Thanks buddy, keep it up!
Started reading about 2stroke theory back in the 60s, it’s complicated. Rode 2stroke motorcycles in the early 70s- porting and pipe making a world of difference in how they ride.
That's a helpful video keep them coming I've been getting parts to attempt my first 372 build you and Harvey are great inspiration seeing your videos is what made me to decide to try porting and playing with pipes made one of Harvey's for it my goodness its loud and narly but definitely made a big difference
Thank you for sharing your knowledge and tips with us! For years I've been right at home inside of 4 cycle automotive engines. (GM small block, big block, 3.8, Ls. Ford 2.3, Cleveland and Windsor. Honda F/H, B and K series. Likely more I'm not thinking of) bikes, ATC's, quads, lawn equipment etc... but 2 strokes and their theory were a foreign and honestly intimidating thing to me. I've done a few 2t ATC/bike top ends but didn't even dream of modifying any 2t engine. NOPE! Lol. Thanks to you and your wonderful explanations, 2t engines make perfect sense to me now! You were the person to open my eyes to the world of chainsaw porters/builders on YT! I'm still very green but learning and have no second thoughts about "cleaning up" or tweaking port shapes in saws. Haven't gone far yet but have seen very noticeable gains on a few saws so far!
Long winded, late night thank you!!
Very good info. One thing I have learned is port velocity and exhaust scavenging. When the exhaust is pulling the gasses out due to velocity, you actually suck fuel and air out of the transfers, which creates more velocity in the transfers and crankcase. So exhaust has a ton of importance to allowing the pump to actually flow. Just a little thought to keep in mind when you look at blow down and intake port vacuum.
What about a reverse cylinder? With a velocity stack..? Wouldn't this help velocity through out the engine?
@@asphaltcowboy7868 that all depends on the design of the cylinder. If you impede flow by reversing the flow, it's possible to get a reveres flow/swirl affect. That would most likely inhibit velocity in many areas. The more you get out, the more you get in, and at a given rate of time and speed, the more power you can create. It's all a balancing act.
Man this cleared up a couple questions I had, very informative!
There's many of us that move a lot of air both low and high velocity and we'r not in the HVAC game lol! Thank's for sharing some of the inner working's of the two stroke world with us Tinman take care.
I like the thought on the intake timing with vacuum or amount of negative pressure it creates but you're still increasing volume in the case from bottom to top thinking about it and on the way down if you have reeds like in a snowmobile it should compress all the air till the intake closes then all in the case till the transfers open. I do get the initial high energy pull to get the air moving with the extra vacuum as the intake cracks and how that would help with response or acceleration. I ported a 562 3 or 4 times plus opened exhaust, opening it up the ports more and more and ran it next to another modded 562 that had a decked jug and cut "pop-up" and modified muffler piston and they were toe and toe but I went as far as case porting when I had to weld up the bar oil tank. I'm currently looking at an air cooled yamaha sled and how I could get some extra power out of it with porting
Great video. I have recently built a 372 big bore using information gained from your channel and the Ironhorse. The finished saw starts good, idles great and is a very strong work saw. I have made a couple of pipes for this saw and the one that seems to work the best so far is fashioned very similar to the pipe you built for Hogan's 266. As you say all the time, it's about moving air!
Hey tin man watch all of your shows. You are an incredible guy with a chainsaw and fixing it. I wish I was half as good as you. You are an awesome mentor and a good person to watch on the tube. Awesome, thank you for your time and your patience sincerely woodcutter. Anthony Washington State. If you ever come up here, come on up Washington and got some nice big trees and some big sauce. If you wanna try some. I like your opinion on a lot of Chainsaws and stuff
13:05 to answer your question. Gas mass velocity and reflected impulse energy. The exhaust pulse and the energy release from the cylinder that both travel at different speeds cause a vacuum to exist in the cylinder. This cylinder vacuum through the transfer ports preconditions the lower chamber to additionally draw inlet vaccum on the subsequent cycle. As the cycle speeds up the mass column on exhaust and inlet become more significant till the rebounding pulse energy is overcome by restriction, phasing and frictional losses. So it's not just an air pump it's also tuning energy gradients.
On small piston port engines I found the best way to experiment with intake timing was to grind that side of the piston skirt 0.5mm at a time until its gone too far then go back one step. Altering the cylinder port is actually better because it also increases area. Pistons are cheaper than cinders tho lol
Thank you for all that you do. your helping me so much. I am with you on the transfers.
Very interesting to consider, I like a nice responsive nice idling saw for climbing. It's nice to have a screamer but if it's slow to respond or idles poor it's hard to use. Almost done my last 346xpg with close to stock timing, lightened and polished piston and freed up exhaust.
Cool video about Long and short blowdown . If you run short blowdown less time to compress so then you can't open your lower transfers as much because there is not as vacuum or case compression. But if you run longer blowdown it has more time to compress so you can grind more on your transfers. I guess it is like a combustion chamber the smaller you get more compression the bigger the less compression.
I love your videos and I'd love to see you do something on motorized bicycles just cause the torque aspects a little bit different it'll be something new for you to learn and you know enough to teach us about it
First time seeing a cut out was on this channel and transfers made sense.
I simplly don't know about the engineering part of it, my intention is just to repair them not to modify them nor build one; but it is interesting listening and seeing how the 2-stroke operates.
Thanks for the video. Good info.
I do wanna say great video and great information!
You are a great porter looks clean
Thanks for the info. Is there any gains in making the lower transfers higher to match the piston.
Thanks for the ❤ on my earlier comment ( grinding piston skirt ) pardon my ignorance I'm a motorcycle guy and 2 stroke but I know very little about saws, what are the ideal power characteristics? I doubt if midrange is as important as on a vehicle and I'm guessing a long over rev past peak power rpm so rev the thing to oblivion then start the cut and when the load comes on and rpm is dropping the torque increases?
If you ask 10 saw builders "what's the ideal...." you'll get 10 different answers.
I like quick reving and lots of power up top where the saw spends life.
2-stroke MX bikes are all full circle cranks for tight primary compression, which helps the reed valve open earlier. It does not matter what track they run on in that respect. That may not have been true in 1971, when the Jennings and Bell books were written, but they are all full circle cranks today. The father of the modern 2-stroke may be Dr. Gordon Blair, but I have not read much of his stuff.
From what I understand, "blow down time" is about the cylinder "blowing down in pressure" to zero pressure, before the transfers open so there is no pressure left to resist the transfer flow into the cylinder on the down stroke, at the rpm's you are running at. Personally, I don't adjust blow down time at the transfer port roof, but there may be some power there.
Hi Tinman!
Great fan of your videos!! Greetings from Athens Greece 😊
I got a Husky 50 - open transfers . It would be great to make a video dedicated to open transfers porting , tuning etc!
Thank you very much 😊
I really enjoy your video you’ll learn a lot from your videos keep doing them have you ever did any work with motorized bike motors to screw
I'm just trying figure out great 372xp work saw porting.
Thank you for sharing this.
Changing transfer or port timing is similar to changing a camshaft in a 4 stroke engine……you may lose suction or vacuum just like adding more duration in a camshaft for a 4 stroke….loss of low end but will gain top end power….adding compression will help compensate…granted that may be hard to do on a chain saw …
Re : expansion chambers. I’m under the impression that the expansion chamber on a 2 stroke acts as a higher pressure space (than atmospheric) after the combustion chamber that aids in pushing exhaust gases backwards into the cylinder. In order to optimise power and response, the shape and size of the expansion chamber is tuned to help aid this process. If this is correct then back pressure plays a major part in the efficient running of a 2 stroke. Is this correct.
I am not a 550 expert (I am a 488 guy), BUT....That Polaris 550 is a Piston Port with a reed that controls that extra intake to case port.
On the Polaris 488 Twin and the very closely related 244 single Polaris ATV engine...The ATV and the Utility Snowmobile engines run a Longer Piston Skirt (Shorter intake duration)....To make better low end torque, more case vacuum (Powerband is around 6000)....VS...The Trail Sleds run a Shorter Skirt (Makes Longer intake timing - along with other porting stuff) to push the Powerband closer to 7200... The Liquid Cooled 488 (aka 500) uses the same piston as the Fan Trail 488 Engine but has hotter porting timing, pushing max power to 8000 (and of course more compression/No Big Fan to spin) - I have had better luck with 488s than 550s - Just my experience.
Great video.... Now I've got a question. So you said if you increase the rpm 5000 then the cooling fan spins 5000 more rpms as well. Totally agree with this . Now honest question time. On a boat, you spin any prop to fast and you get cavitation. Can this happen with a cooling fan on a saw? I don't know I'm not a rocket surgeon at all just wondering if there's a crossover. What do you think?
Well Air and Liquid in theory are both a "Fluid" and YES...An Aircraft Prop is more efficient at lower RPM than at higher RPM and on some engines you can push the tip speed faster than the speed of sound...which makes a snap that is kind of (to my knowledge) a form of cavitation!
ylösvirtauskanavien purkaus aukot pitää olla aina mahdollisimman matalat mutta riittävän leveät. Virtausnopeuden takia ja myös tuon kampikammion paineen takia. Mutta toki pakoputken pulssit sotkee ajatustani ja sitä mikä on todellinen tilanne eri vaiheissa. itse olen pilannut yhden sylinterin liian korkeilla ylösvirtauskanavien purkausaukoilla. Jonkun pitäisi rakentaa sylinteri jossa on läppäventtiilit myös ylösvirtauskanavissa. Ja testata miten se vaikuttaa.
I think you just solved my idle problem with my 066. I accidentally lowered the intake timing and I can't get it to idle down enough for the chain to not move
That may be you issue. Too much intake timing will.cause the saw to be rich at idle sp it will need to idle faster then stock or it will often choke itself out.
@@tinmanssaws thank you
What i have learned is many people cant widen and polish ports but very few people actually understand what everything is actually doing in a two stroke.
I am of the mindset that long blow down 28-30* reduces torque but allows higher peak rpm. I also feel that if transfers are raised, intake floor should be raised the same amount to maintain Crank case compression, it is very important, 40 degrees of crank rotation is how long case compression should occur. If you want a piss revver with no real power, lower the intake floor. Also, the much touted dual port muffler reduces cylinder pressure sooner, therby Effectively raising transfer ports and allowing transfer flow to begin sooner.
Me likes powersaws….!
Also, Setting squish @ .020” and adding dual port muffler and a free flowing airfilter is a damn good, reliable setup with minimal effort.
Very cool thinking, its right i think
I'm currently working on a motorized bicycle engine.. not saying I wouldn't or won't..cause my bike is already running really good, but just out of being curious.. what do you think about swapping out a dome piston to a flat-top piston? Of course the bottom of cylinder would have to be resurfaced to make up for the quench gap..but wouldn't in logical terms a flat top Piston mean less blow-down and more down force on the piston it's self??? The pro when it comes to dome is a tighter quench gap (more compression) but the con is..the down force is directed over the piston and into the rings..
😂😂😂👍. “ not just with my yapper!!!” LMFFAO!!! How freaking funny is that!!! Dude…I absolutely love the laughing while learning together kinda mojo that makes you… you! Love your style of let’s learn about this together… 😂👍💪😉
Mr Tinman......question about unlimited coils for the 372. what are the gains, losses or downside of going that rout as opposed to full porting a work saw? thanks.....Jim
Great video!
Hi Mr Tinman, I look at all your educating videos with lot of gratefulnes, thanks! Could this sucksion area be told in degree’s, and be related to lower transfer area and volume?
Wont air volume and pressure differences influence that suction too? If you raise the port on top, and flow the bottom but opening it at the same time, that will increase air volume in the case, which will slow down air movement. So although you have better "flow", you also lose air velocity. Or am i wrong?
Have you dug into any of zenoahs engines? The g230 g290 and g320? Those engines rip.
What was the book he referenced in the beginning
If you open the intake timings too much, or if you widen the lower transfer ports too much, you generally get a rather slow saw.
A lot is not always the best.
Are you taking into account for the tune section of the exhaust? A good exhaust will be hurt with porting. The exhaust acts as a vacuum and a wall
Hi, chainsaws don't have tuned exhausts so the rules don't apply the same.
Man I have a Echo 670 and I don’t ever remember a saw that has that kind of compression it’s they only saw that I put my foot in Handel to start and I can pull it free hand but it’s safer to put you foot .
Hey tinman bought a blown up 562 going to put together a port plan
When my bb 372xp is at bdc, are my upper transfers supposed to or better if completely open like uncle harve did his piston, I got big squish and my bdc kinda covers the transfers, file piston to taper to the transfer? Talk to me tinman!
I've always liked staged blowdown with quad transfers, keep up the great videos... Does static pressure count in 2 strokes? Lol. I'm a sheet metal journeyman in Alberta.. But went the custom route
Different with a pipe. At high rpm pipe is pulling fuel thru the carb over coming the pistons pumping ability.
That pro mac 55 is it able to be modified? I have one just curious.
what year is that flathead on the shelf behind you
1942
I would love to see you build a snowmobile engine chainsaw that would be bad ass lol
What chain saw runs at 13,000 rpm? I did not think any of them rev that high.
Like the video, interesting stuff. But you use too much vernacular for it to really land with most, I’d assume. Myself included.
1 ring on a 2 ring type piston ? top or bottom ?
Top only.
👽👍🏻
I'm new at this what about a Stihl 034 AV ,planning mild port work and some exhaust polish finishing.but I got a question.What would an expansion chamber pipe? How does resonance work on a chain saw...versus motorcycle
opening up the transfert port will not allow exhaust pressure to go back into the carb
With as successfully as this channel is and you knowledge have you ever though of checking out the 2 stroke bicycle kits there 38 to 40 mm stroke you may can make a beast running a ms660 head and piston
Let's talk hard truths bumping the compresion is really fuel dependent you could go way high and run e85 and even with stock port timing see a 10% bump in power with not alot more usage of fuel because of the increase in efficiency all while the saw is actually cooler running. Now porting probably gets you 10-15% over stock but you are always trading peak power for losses in idle/ starting and fuel use the higher you push but a good pipe has shown to be good for 50-60% more power just bolt on and go with a carb adjustment
might have to watch this a few times to really get it!! i will eventually! haha i'm old school! and old
IMO. Shaping the lower transfers like that and leaving the top end of transfers stock. Creates a ram air. Just my opinion
nice well done
I have always wondered why blowdown is important because I cant see what the point is. However time from intake closing to transfers opening is something I consider much more important. I just built my husky 444 acording to the jennigs method and with the yamaha numbers jennigs talks about. I have to run it in bigger wood before I can say if I succeeded or not
I could watch this video 100 times, great information. Just watched Harvey running his stock 372, check it out. TC Mahalo Tinman 🤙🤙🤙
Does anyone know where to get a recoil cord pully for a 44 husqvarna? Or the whole recoil?
Even cutting the piston skirt helps also!
2st theory part ~ 😊
The best idea for heat is to have a pipe on the Saw so all that heat goes away from the cylinder instead of sitting against it
your video taught me alot, should it not.
👍👍 oke bos 👍
Hey!
Lowering your intake increase the time in which air can enter the crank. So why doesn't it increase suction? A higher intake means that the crankcase only has time to be filled at very short time when the piston is at the top
Suction is created when the port is closed and the piston is travelling up.
There's a balance between building suction and opening the intake port..
@@tinmanssaws The intake suction continues to TDC. But it is flowing as soon as the skirt opens the port on a piston port engine. The reason why a lot of intake duration will hurt lower rpm's is because at those rpm's, with a slower intake velocity, the pressure of the cases on the down stroke starts blowing back into the intake before the port is closed. But with higher rpm and air velocities into the intake, it can help a higher rpm engine sing with more time to fill the cases.
You should get a rotary car. shits basically a 2 stroke
😊👍👍👍🌎🌞😊
Sir i have two stroke cylinder i want to increase its rpm power please help me how i can increase the speed from its ports. Please help me tell me sir
A KTM 50cc dirt bike stock makes over 9hp, a 65cc makes 16hp, and a 85cc makes over 20hp. With chainsaws, your lucky to have half that hp per cc.
You came here just to say you know nothing about saws , congratulations
The bikes have gears so can have a very narrow powerband, I'd imagine a saw needs a bit more torque, I know next to nothing about them tho, I'm basing this comment on single speed kart or scooter engines.
@@madmaxsdog8040 actually a saw pretty much runs at full throttle to a dirtbike needs to have power every where. A bike also needs more torque
Crankcase pressure and volume is very important,and yes imtake timing and uppers timing can effect it ,tell me why the hell do you hog your lowers so much, increasing the volume so much, obviously haven't tested that theory
YOU MEAN FRICTION ? RINGS MAKE FRICTION A FAN WILL CREATE DRAG AND SO WILL THE IGNITION AS IT MAKES POWER IT WILL HAVE MAGNETIC DRAG ........
Actually at high revs the magnetic issue "cogging" negates itself and the ignition timing can take advantage of this with the right coil, spark advance can be induced. The flywheel fins don't create much drag after a certain speed either, as they are a very crude centrifugal fan concept and the air stalls. This is also why he is over confident with it being adequate for a "hot saw" ( performance modified).
more power more energy more heat ,,,, if you tune for power you need to use water cooling or minimum larger head finnage and bigger fan pass more air.@@mrgoodman6620
at what rpm does the magnetic drag trail off?@@mrgoodman6620
its true if u raiese ur exaust transfers and intake u will have less suction and pumping BUTT its fine untile it makes more power
I know that "snowmobile cylinder" it's not liquid cooled and doesn't have power valves. Lol