At 10k rpm, that piston is changing directions 333 times per second. These machines astoubd me. This is an outstanding video that offers a beginner a complete understanding of what happens through one revolution of the rotating assembly. Way to hit it out of the park with this one!
Tinman Great video !! I Learned A lot... I would like to see basically the same video but with the Timing Wheel installed Im Losing the lesson when you talk about the #'s ... 2 strokes are new to me @ 61 years Im still learning and Im Hooked on this channel...Keep up the Great Content .Thanks
You are exactly right about blowdown, a properly tuned 2 stroke the exiting exhaust actually assists in bringing the new fuel/air in and getting all the exhaust out. Then there is the exhaust rebound you discussed which shouldn’t be confused with back pressure. It’s simply a pressure wave. It does push a bit of the excessive new fuel back into the cylinder after the intake is closed but just as the exhaust is closing, to increase the compression and put more air and fuel into the cylinder to fire. This is why tuned race saws have a cone shaped end before the exhaust exits, this increases the duration of the pressure wave maximizing that extra fuel air stuffing. It’s very much like adding a turbo or super charger. Longer blowdown quite simply allows the explosion to put more power into the crank. That fuel efficiency. There are obviously limits as you have found.
i love this stuff!!! thanks tinman. so a short blowdown saw would like a bigger opening in the muffler, to drop the pressure in the muffler faster. recently, either you or Harv was saying something about a lot of snowmobiles being very oversquare, how does this relate to a lot of them long blowdown?
Man I’m like a sponge just taking all this in and I can’t get enough! Im starting to get a group of saws and working on getting everything i need to start experimenting. Degree wheel, a dremel, mics, scale I can’t wait to start my first one. Im going to be super cautious probably won’t change to much to fast but I just want to do my first base gasket delete and muffler mod! Lol I just can’t get enough info but your videos are a HUGE help. Thanks and keep it up!👍
You do a great job relating information, I've been a diesel technician for 15 years and 2 strokes have always been like wizardry to me lol. I've been collecting saws for about 2 years now and tinkering here and there figuring out what makes them tick but your videos have definitely shortened the learning curve for me and gotten me excited to start building and porting saws.
Shine a flashlight thru the exhaust port into the cylinder, then look thru the spark plug hole to see when the piston cracks the transfer ports, then just read the timing wheel. You can also use a endoscope thru the plug hole and look for the same thing, whatever the difference in degrees between exhaust opening and transfer opening is, is your BD # in degrees.
As always, perfect explanation👍 love the cutaway! The way my mind works, I've always been able to visualize flow or fluid dynamics. So I totally understand what you mean in your explanations. Would love to see mufflers/pipes in this series! Take care and stay warm aswell!
Love the informative content Tinman, keep it coming! I'm going to be on bed rest for at least another week (burried an ax to the bone on my left leg) and it's killing me not to be out running a saw!
Excellent video! Love your content. Keep the info coming. And figure that echo out so I know which way to go with my 590 I’m an echo fanboy I can’t help it
TIP: Take a look at the flywheel, bring the saw to TDC, Just above the coil, on the case, , , ,there might be a timing mark. There also might be one on the flywheel. Results may vary, , , I am working with an OLD type 1, stihl028 (it uses 4mm cap screws, not T-27s. Measure the distance between the marks, and the circumference of the flywheel, , ,,calculate the timing advance (I am calculating 12 degrees advance). I don't know if there is an electronic advance in addition to that (from the coil). As Always, , ,Thanks for the presentation, , ,I have learned so much.
I think you should do a video on the ms500i,they tend to have shorter blowdown and higher intake timing numbers. I think it would be neat to discuss this a little more.
I agree with pretty much everything that you’ve said…. Except the “modern 2 stroke thing”… I feel they are just so choked up in just about every which way.
I run the 66cc 2-stroke bicycle engine I've had several and they don't run the same. Quality control really isn't there. You have explained to me how to properly time and tune
Great vid Tinman! I agree with your technique. I'm gonna tell my missus about this vid. Lots of short blow down, lots of longer blow down, lots of stroke, lots of pulling......👍🇦🇺😂
I've had 2 stroke engines all of my life, and now I understand how they operate. I am rebuilding my first saw now. I am staying stock and hoping for a running saw. Your videos have helped me so much. Thanks again.....
Hello Tinman, once again a very nice and informative video. Today I also watched your carburetor tuning video. Could you sometime explain how and why a four-stroking engine leans out under load? Thumbs up and greetings from Germany!! 👍
Very good explanation! Now it starts to make sense why some ported saws seem shaky or stutter-ey. The pressure from the bottom end, top end, and exhaust must all be kind of fighting eachother, eh?
I'm going to have to ask Santa Claus for an extra pack of notebooks! I'm literally filling them up every time I watch one of these videos. So well done! 💪👍
Bro, thanks for helping me understand timing on a 2 stroke. I've been only into motorized bikes for a couple of years now and I still knew nothing about what was going on. I was just putting kits together and riding like that. But I have enough engines here where I don't have buy new and just fix these. Your channel is helping me achieve that goal. Very, very , informative. Absolutely great work. Thanks. Build break and fix channel does that cutaway too. Great work. I'm getting better at putting my engines back together again.
So raise the exhaust port and widen upper transfer... is the way to look at it, shorter duration and quicker recharge for next cycle. But all within the optimal timing values. Very stoked about this tutorial. Thanks again Sensei Tinman...Mahalo🤙🤙🤙
I wish i had u as a small engine teacher in school. This makes sense , we werent allowed to touch 2 strokes. I just figured we had valves someplace hidden. I had a 034 that was hard kicking and destroyed pawls. Then my bearing seized and spun in the case. I wish i tore it apart when it was dead, instead of donating it for parts. This is absolutely fascinating
I'm a newbie wanting to do a port polish job on small 2 stroke bike engine....Would it be safe & add power to bevel/round the bottom lip of the intake port without lowering it no more than a 1/2 mm for better intake air flow, then bevel the bottom of the intake side of piston skirt, bevel the top lip of the exhaust port without raising it no more than 1/2mm. Then polish the exhaust port and polish the open transfer ports or would you want to leave the transfer ports roughed up for more turbulent airflow like the intake?
Short answer, lowering your intake and raising your exhaust could possibly increase power as long as you dont go too far. Its hard to say what would be too far without a timing wheel.
