A perfect video explaining cause and effect of changing blowdown, deck height,and exhaust pressures! I agree 100 %! Spot on information!

Great explanation of reversion and blowdown, I always learn something here👍🏻

Thanks for the great information!! I've done small porting on dirt bikes and snowmobiles all my life ( nothing drastic) and today you have taught me some great information about the timing!!

Charlie, this video is one of the better videos out there. This helps people like me a tremendous amount. I am very grateful for people like you and Ironhorse and Tinman and others. Thank you

Of all the timing videos I’ve watched, you my friend have the best explanation yet, by far. Thank you

For what it's worth, I've ported 3 saws mostly because of the information you've put out. I watch others as well, but I connect with your videos the most. I'm VERY happy with the second Husky 359 I ported. I bought it dead and put a Hyway top end on it. You're right, I gives a great sense of accomplishment. Thank you for continuing to help us newbs out.

That was one of the most informative and useful videos of understanding and learning how 2 strokes work and how everything influences the efficiency and output and what to do and not to do. Thankyou very much. Ive stated off with chainsaws and weed eaters and snowmobiles, and now I have a 80cc 2 stroke kit on a bicycle. Absolutely love 2 strokes. Appreciate it

Very well explained. I admire your integrity in sharing this. Thank you!

As a professionell 2-stroke tuner I observe similar effects. Blowdown bellow 21 is good for mopeds in need for a wide powerband. But when it comes to higher power I use 23-26 degrees of blowdown. Mopeds have an inherited advantage: the longer exhaust system where we adjust the frequency and intensity of the return pulse in order to minimize reversion. Your adjustable exhaust system mimics this effect on a very small space! Great tuning 😍

Love your variable tuning pipe idea to let you test and find your saw’s preferred exhaust configuration… sweet idea!

Man I sure appreciate you sharing your experience and knowledge to help us. Great job with the blabber factory, you did great explaining.

This is a great explanation video of how your saw works… every starting saw builder should watch this video! A+ buddy!!!

I'm new to learning about exhaust systems and I'm glad I came across your video sir!

Great video! I agree with your tendency towards more blow down especially when talking about work saws.

The adjustable exhaust system is a freaking awesome idea! That's just a damn good idea. I love that! Get all the scavenging tuned perfect before a muffler/pipe build. Would also give you a starting point to build pipes in bulk of you port the same on several "work" saws. Like the 4910 or 7310 work saws. Great video! Love the educational content!

See you learn something new everyday. I 100% agree with the suck back, some how I’ve over look that little detail all the years I’ve been around small engines. I took small engines in tech school and worked at a small engine shop for 8 years. Great video explaining two stroke porting & theory!

So i heard johns custom saws say that you want your intake to open after youe exhaust closes. I couldnt figure out why until now! What a great video!!!

New here and this is a great video, thank you. Been playing with a Husky 51 and Styhl 028. Porting if you want to call it that. I was having a hard time with the blowdown concept and now I think I have it. I like that you give your numbers which gives me a basis to work towards.Back to the shop in the morning and the timing wheel. Thanks again.

Best explanation it removed some mystery for me thanks

I think you do an excellent job of explaining things. I'm pretty dense and get what you're saying. Thanks.

Love your explanation of blow down 👍

School of hard knocks ain't cheap been going to that school for a long time working on my masters lol Been porting saws for many years You do a pretty decent job of explaining your theory! I've always tried to explain the balance to customers when porting you got to build the saw to the customers needs and cutting style as well as application and conditions Thanks for putting your time out there

Thank you. This was very clarifying to me.

Thanks Charles. 👍

Nice video, good work man!

Thanks! Great explanation.

The problem is that 98% of us don't have lathes or mills to cut the squish band.

Great info many thanks

Great stuff. You da man. Thanks for sharing.

I plan on porting someday! I’m at the phase where I’m just diagnosing and fixing saws. But I’ll work my way up. Thanks Charles!!!!

awesome description on 2 stroke theory.

thanks Charles. appriciate you wisdom. saving us all time and money.

Thanks, that's really clear and helpful.

got a good idea about what reversion and blowdown is. thanks

I just ordered a degree wheel and I'm going to try some of the tips and tricks I've learned from you and a few others that you know and are friends with, to start the build on my first full port job! Wish me luck man, I'm gonna need it. Lol

Thank you for the video. Make similar videos and feel the same way when trying to explain the porting tricks and what they have actualy done in performance and throttle response. That feeling of accomplishment after you made something that was meh to scary impressive is the best feeling in the world

Everything you said makes sence too me. Cheers mate

Great video that made awesome sense and I would love to try something like this on my Kawasaki 2 stroke

Great information thank u sir

Awesome explanation bud

Love to sit down with you, Flagg, Walker, Dyno-Joe, Ripsaw, and others to hear your ideas about your builds and why.

Thanks for the info my saws are running good enough without burning up the bar but my old Tm 250 Suzuki might benefit from this info .

Great video ! You just showed me how to go back to a motor I ported. But ruined it. And reevaluate my numbers. I think now it’s problem is blowdown. Thanks for the information I really appreciate your vid’s

Just watched this again I'm learning

I want to get my 590 timberwolf ported. Or do it myself. Your videos are awesome

The black art of chainsaw porting! Thanks for the lesson, great video

Really like that adjustable lenght pipe idea, should allow getting it just right. Might be more hassle that it's worth but you could adjust it for different kinda of cutting, ie bucking vs limbing

Charels, you have a great approach. Air is elastic. Great idea for the variable tune pipe. Truth is, because there is variance on every saw - an adjustable pipe would be a great design, and something that could become a decent product. A broach to clean up the weld on welded pipe for a cleaner, truer bore - and have a range of available sizes based saw displacement. So, one (field tuneable) pipe would be 60-70cc (with a disclaimer of course) another for 80-100, and one for 110-125 102° is also nice number because even if you overshoot just a degree or two, you've still got a rock solid work saw rather than a "coulda-been a LOT better. It's easy take more later if it's really not awesome at a more conservative roof height. People who want to bicker with you bicker with everyone, so, you're no more "special" than anyone else "actually doing something." The "bickering people" bicker with everyone equally - overall. If 1/3 of the people you interact with thing your full of - constipated - or are angry with you over some pretty minor this and that - you're probably doing exactly what you aight to be. :) 1/3

Two thumbs up!

Thanks man for you video

Thank You!

I had a ring snag in my upper intake port can I port it a millimeter or two away from the upper intake port as like a bevel kind of deal so I can save my cylinder hopefully and if I do that, what other changes do I have to make if you don’t mind me asking. I’m trying to follow this video the exhaust makes sense. I just didn’t hear much about the intake.

That makes sense I just built a Ironhorse style pipe like that 1.5 main pipe 4" long with 7/8 exit. It pulls but at lower rpm and couldn't figure out why now I'm going to shortin it after seeing this!

Great video,its easier to show how the engine works with a cutaway block.It made me think about how not running the second ring would allow the transfers to communicate with the exhaust on the up stroke, causing it to suck exhaust through the ring groove.

good video bud

The design of that exhaust port reminds me of a fueling valve. That valve will actually improve exhaust extraction and prevent backfire, so your theory is based on existing technology. It would be interesting to have a straight exhaust port with a cone in the exhaust pipe. You could flip the cone either way and see what effect that would have on performance. Also you could move the cone in or out and test performance that way. The only problem I see is the tuning would be saw specific and not universal. I don’t see any heat problems with this setup as the gasses are more free flowing. I believe heat issues come from high compression application, but higher gas concentrations would tend to cool that as well. Just think where we would be with two cycle without the stinking epa.

Great video like your views !

will reversion cause fuel-air ti stand off from the carburator throat? im thinking the saw had a plugged exhaust. peobably a sparh arrestor

Many a books have been written on porting theories and the advanced social media tips and tricks on how to get the most power out of a two stroke there is no end. Imagine if you will if one can advance the technology by using sensitive thermocouples to variably time the ports at any given load, temperature and demand of a saw when needed and the ultimate power under every given condition would be amazing and an undertaking that would take quite a while to achieve the best volumetric efficiency that a saw would have would be awesome.

I cant lower the cylinder for my ms290 cylinder because the crank case seal seats are built 50% into the cylinder 50% in crank case . could definitely do it with bigger cylinder with flat base like like ms440 for example. But yes great way to gain blowdown as you mentioned. If you do deck the base of the cylinder & the piston makes contact with cylinder at TDC You could probably take some material off the top of a flat head piston keeping it flat & or ramp it to gain more blow down if you can’t port any further or want to keep port numbers

Keep in mind exhaust port area will affect blowdown.the numbers don't tell the whole story. The faster you can evacuate the exhaust gas the sooner the transfers can open. exhaust width is very important.

Thanks bro

saludos desde venezuela... buen video..

Awesome video Charlie!

What about a washer like you were talking but using a spring behind it I wonder if it’d tune itself…theoretically “optimum” throughout the rpm band…be fun to try

And purchase what I thought was 50 CC's however the Pistons 47 mm across by 47 m down and then like connecting rod is stamped FM80 CAN YOU TELL ME WHAT I HAVE HERE IN CCs?

So how do you obtain the blow down,do you file the port down ,while watching your video and heard you get more gas into the fire chamber which you said to much is bad then why port

I have never seen carbon deposits in transfer ports, usually l was told raising them make more hp and a higher power band?

250 polaris boss i just got new piston rings both rings marked same wich is top ring

Just wondering have you had any success with changing crankcase compression

Those pipes are designed pretty much identical to the nitro r/c racing pipes I used to run in the late 90's.

Amen sr!!!!

👍🆙CB, Has your thoughts changed any since making this video?

A combo of compression and more blowdown ? Correct?

I’m working on a Jonsered 510 or 520 and I can see the piston ring through the intake at BDC! I have future plans of lowering the squish about 70 once I get a lathe which will solve it. I’m just curious how it will affect performance until then

Well done Charles!!!!

Since you are mentioning blowdown a lot with the two stroke..im wondering if I was to swap out my stock dome piston to a flat-top piston, would this make any difference???

I’m all about leaving all my exhaust duration and I leave them long for as much torque as I can get… I don’t expand my exhaust port window’s as I think most are too big to start with… My thinking is very close to yours partner… there’s lot’s of videos of saw’s reving and cutting a couple cookies but I’m all about keeping my saw’s extra rich and not allowing them to free rev into the upper stratosphere… I don’t need to spin up that high…I’m cutting at 11k or something less than 12k so I’m good right there… I love my little bearings and my crank and I want to hug them and squeeze them and give them lots of oil in my mixture and not spin them too fast! 😂😂👍😂💪🤪🇺🇸💪😎. I like the longer bar and less bending over… my short legs like a 28-32 inch bar… a 36 or 42 I have to lift it and swing it so I’m not dragging it’s tip on the ground… that’s more work… I’m lazy and I always look for the ways to get it done easier and faster and the cheaper the better!!! LMFFAO!!! When I was younger I was a rammer and a hammer and gammer… if it doesn’t fit get a bigger hammer type dude… in my older age I’m more into the “just enough to get it done, kinda thinker.” 😂😂😂. You can cut a lot of tree’s and wood with a good built 50cc size saw… and not be exhausted at the end of the day… 😉👍

How are u getting transfers done with the harbor freight rotary tool??

When you say you increase blow down, does that mean you are raising the exhaust port?

If you could see yourself the way I see you, You woulden't be so critical of yourself. You Rule at what you do in my eyes. 👍

Did you ever build that custom pipe for the echos?

👍

More compression, more intake, more exhaust, more fuel, it only makes sense to have more blowdown...

I too like more blowdown

How can you get more blow down

Darn EPA. Its all about emissions. Its all about balance when it comes to porting.

Your videos need to come with a warning. Now my saw makes more HP than my Toyota Camry lol

I am a firm believer in getting the spent charge out and away from the saw as quick as possible! These EPA idiots have tried to use the exaust pipe as a way to catch the hydrocarbons and spark arrestor, and Baffles, That's way too much crap for the heated burnt gases to be trying to make its way through to exit the engine! I believe it is the root cause of all the newer stuff over heating and cooking a piston! All I know is everytime i pull the muffler and drill a hole in between the two bolts that hold it on the cylinder it's a night and day difference! And if I have to cut on federal land I put a spark arrestor back in the pipe so I don't have any issues with the law or worrying about catching the woods on fire! Last time I checked your equipment won't be spitting sparks anyhow if you operate and maintenance them properly.

eliminate reversion? jee, why are all the engine designers so stupid? MAYBE it does something ???

Frequency resonance....a beautiful thing.tunning is a science and an Art in a way. To get that crisp rpm followed by hp when cutting deep is satisfying. I run 102 octane Vp with 927 castor. The performance and smell❤..lol. film strength with a 70:1 mix ratio freed up some ponies alone.

recently watched a tinman video on long blowdown. he likes a lot of blowdown too, but he didnt go as far down the rabbit hole as to why long blowdown makes good power.

two thumbs up!!!