people have tried - the main issue is reliability - the exhaust is hot and you need an air tight system that can take the heat (thermal expansion) and all the carbon and shit and still work time and time again
Alright fanboy. This channel has a better vibe, Matt is funnier that Jason. Also, Jason does a lot of sponsored videos where he tries to sell Shell Oil.
Really good explanation. Thanks. I now think I see why putting AllSpeeds on my RD 400 gave it more power, but made it very peaky compared with stock exhaust?
nice vid, although i more or less knew this, it's nice how understandable is your way of teaching, i have to give you that. one question though, and maybe you can address this in a future vid - how does the height of the exhaust port change how the pressure wave travels and what time does it arrive back at the piston. i've heard that the higher the exhaust port, the more rpm the engine will give. cheers - nick
How’s come 125cc dirt bikes exhaust pipes come out the cylinder then turn around the frame and go out the back, where 250cc dirt bikes come out the cylinder, turn left, loop back to the right and out the back? I’ve always wondered
its about the length of the expansion chamber and bigger bore engine needs bigger and longer chamber to handle more gas than smaller engines pipe, hard to explain because i´m not native english speaker so somebody else can explain better
Check out CVEC exhaust pipes for nitro RC engines, I've had one of these pipes before. It's a tunable 2 stroke pipe. It has threads inside that holds a baffle like a firearm suppressor. Twist the baffle and it moves inside the pipe. Then you screw the pipe back together. It has 3 pieces. Two pipe halves and a baffle.
yes but it is also a function of the system. If you remove the exhaust most 2 strokes can't maintain continual combustion. So its also an intergral part of the design in most cases.
At peak efficiency, it acts not only as a valve by creating equal or slightly greater back pressure in the returning wave, but after blocking the fresh charge from escaping, it'll leave a low pressure wave behind it helping pull the exhaust out after combustion. The best way to give you an example of pressure waves is with a wave machine or your hand in a pool of water. You'll watch the waves run out big and fast then bounce off the wall and return wider but about as fast. if you time it right, you can make the waves bigger without increasing energy. in a 2 stroke, any charge that leaks into the exhaust is actually a loss of charge volume making their less to compress meaning less power. Air has mass and inertia when traveling from the crankcase to the combustion chamber. Blocking the exhaust port or having trace amounts of exhaust re-enter won't stop the charge coming in but add more volume and act as a catalyst for combustion. Your car does this with the EGR valve to lower emissions. it does the same for 2- strokes also. So, VERY complicated voodoo. But very very cool if you begin to understand it. Everything in a two - stroke is about timing. If you can time your high pressure wave to the low pressure wave on either side of the reed valve, you further increase efficiency. Now, if you want to get really crazy, Husqvarna chainsaws have no......? Reed valve. How do you have a two stroke without a reed valve? Timing, fancy engineering, and probably more voodoo.
At peak efficiency, it acts not only as a valve by creating equal or slightly greater back pressure in the returning wave, but after blocking the fresh charge from escaping, it'll leave a low pressure wave behind it helping pull the exhaust out after combustion. The best way to give you an example of pressure waves is with a wave machine or your hand in a pool of water. You'll watch the waves run out big and fast then bounce off the wall and return wider but about as fast. if you time it right, you can make the waves bigger without increasing energy. in a 2 stroke, any charge that leaks into the exhaust is actually a loss of charge volume making their less to compress meaning less power. Air has mass and inertia when traveling from the crankcase to the combustion chamber. Blocking the exhaust port or having trace amounts of exhaust re-enter won't stop the charge coming in but add more volume and act as a catalyst for combustion. Your car does this with the EGR valve to lower emissions. it does the same for 2- strokes also. So, VERY complicated voodoo. But very very cool if you begin to understand it. Everything in a two - stroke is about timing. If you can time your high pressure wave to the low pressure wave on either side of the reed valve, you further increase efficiency. Now, if you want to get really crazy, Husqvarna chainsaws have no......? Reed valve. How do you have a two stroke without a reed valve? Timing, fancy engineering, and probably more voodoo.
The tuned expansion chamber is in effect, a supercharger, Cooling is the aim of having the exhaust port close just before the burnt products of combustion are forced back into the cylinder, where at high revs and lean mixture, they will raise the piston temperature above the accepted 550C that our race pistons could handle. Above this they would become "soft" and stick to the cylinder. (Nip or seize up).
When I was 16 I had an fs1e moped, the last of the non restricted ones. Will let people guess the year.. Anyway I cobbled together an expansion exhaust to try and beat my mate who had a Puch JPS. It never worked but I thought it created some kind of super vacum at the time. I pondered for ages how it worked and that was the best guess I could come up with. At 16 you know everything so was never gona ask anyone. Later in life I bought a KDX250 and it was only then I understood what they did and how they work... Some of the time.
This is great and in no way trying to discredit the creator, I’m sure it was just a brain fart and he does know the right way but... the subject matter starting at 14:30 he has the explanation backwards. The explanation for the waves returning early is really for them returning late at that rpm range and vise versa for the other rpm range extreme.
could also use holes in the expansion chamber that open and close with valves, like the keys in a wind instrument. if you use a valve with variable aperture then you can get the same effect as a sliding exhaust chamber w/ a much simpler and more reliable mechanism.
yeah, I've not thought through the details. but since the basic task is to modify the frequency of the resonance, and we know that that is a way to do it, it's potentially workable.
nice explanation. so if you have vario transmission- more or less the same high rpms that is no longer a problem? you just calculate your expantion chamber and thats it. or am i wrong?
What happens if someone's chamber has the belly or the constant diameter cylinder a big one, I read somewhere that the rpm range will be a high powerband, but not pick power.
How 'bout a thin version of a cylinder with rings a larger cylinder as an expansion chamber. Would seal, but would add weight. Maybe a valve in the expansion chamber that opens an additional chamber?
How is it that 3 cylinder 2 strokes scavenge well with a simple exhaust? I read somewhere that the timing helps the exhaust pulses scavenge each other.
Awesome video! You explain this stuff in a way even my dumb ass can understand. As someone who has just started getting obsessed with 2 stroke engines, have had to rebuild my cr250 twice in the last 6 months(see dumbass reference above), How would you recommend getting an actual education on this stuff?
Engines of all kinds but mostly bikes and quads. Would love to see a video on your educational background and how you got started and some of the cool places you've worked. Or a link if you already have?
Hey man awesome video ty I truly enjoy and appreciate all of your vids I am new to 2 strokes so I have a quick question for you so does the length of the pipe before the expansion chamber matter because I took my pipe from another bike and had to cut a small section out but to be fair the whole thing wasnt very big and I may have removed about 50% please respond if you can ty for your time
@@michaelhunter9485only part that doesn't matter so much is after the expansion chamber. Everything else matters alot in every dimension. I still wouldn't go cutting any part of it without calculating and checking though.
i was wondering, does the end silencer itself also play a part in performance? alot of the older 2 stroke racers didnt have an end silencer, just the straight tailpipe. did they just come because of noise emissions or do they actually benefit the performance?
"i was wondering, does the end silencer itself also play a part in performance?" - not really. The back and forth of the pressure in the expansion dampens any effect out.
I have an exhaust with a second trail near the front of it, which goes to a reed valve, then through a tube to a filter thing that isn't hooked to anything. what is that?
@@krazykracken1159 can you find the actual unit under its manufactures brand name trade name in the google images section of google search bar and if the ones of us who can draw an instant visual from just the. Written text as some i know can but i cant , show me the address of a pictured gallary namely google images from just one glance just mayne ill recognize it from some other...i gotvto govas my artificial intelligent trojan virus with pups is completely rewoeding every thing asvi typevfaster. That. I. Can. Correct and. It knows as i have. Our purposely. Agravatedvit. And it. Gets. More aggressive ...andvjust. the othwr day. This thing. Discover the program in a smartvphonev designed to antisipate your next. Wording became x rated and let me. Telll you if. How pleasant you become. Viewed. As i am now ..and. ill be. Damned this guy i barly know was rant about his phone thst was completinh. About. The same and thrn what hit us both like a ton of bricks our virus's are insulting ourv creditablity by using the exact wording that was a new attack use thevssme. Word we didnt disvover untill daysv later we just happen. To dicover so now wevknow that. Somsone. Is doing. This to us
in regards to the problem of putting a variable expansion tube why wouldn't you just put a sleeve over the actual expansion tube feeding into the exhaust further back you don't need to worry about seals as much keep yourself thin and cheap underlay for a constant loss system if anyone will see this or understand me
The only issue I have with anything you said was about two stroke being obsolete. They will always have an application because of the cost. Just maybe not motocross. I do love listening to my son's friends talking trash about two stroke because they are so "hard" to ride. Freaking millennials! SMH. I am thinking of restoring a 500 so they can experience REAL raw power. Loved the video. I thought you explained it just perfect without the use of video. We would all still be riding two strokes if not for the EPA in the United States with the whole emissions, green sticker, red sticker crap. There is no way the industry is going back unless the public regains an interest. Way too much money has been spent and too much progress made in four strokes. Plus, they are way more complicated and they can sell more parts and services.
"The only issue I have with anything you said was about two stroke being obsolete." - I get where you're coming from but because of the EPA and the EURO emissions they are obsolete. Horses can still perform all the tasks they used to but as a mode of transport they are obsolete.
by the way the the pressure wave your talking about is a sound wave not gasses has you explained . its impossible for gasses to travel back lol . try studying Blare two stroke exhaust theory , Belfast university
No - your the fuckwhit. You said sound waves and as usual you dodged that bit - always the same from you idiots. Never any answers for the questions just more nonsense.
You also didn't reply to the comment - "lol who the fuck are you . Rubbish you cant get more power with a turbo .The exhaust gasses are scavenged by the negative sound wave entering the cylinder which is determined by the length of your diffuser cone /variable due to temperature , first tuned length ." - So all these 2 strokes running turbo's don't exist? LMAO!
You appear to be a Yamaha guy so this may sting a little.........There is nothing obsolete about the 2018 KTM and Huskies. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-idYvT-BkeNk.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-7NIHDREexJs.html My first new bike was a 1988 YZ 250 and I so wish Yamaha would have kept putting some money into their two stroke program. Technology dictates what is obsolete not manufacturers. They simply respond to demand in order to turn a profit. As soon as the big four realized that after some initial growing pains and massive cash outlays they would be able to A) charge more for bikes, B) charge more for parts and sell more of them and C) pitch the extra service to dealers as a way to maximize profits because Joe Public is afraid to tear into the engine due to complexity, it was a no brainer for them. With that Jennie out of the bottle there is no way they are turning back to two strokes unless demand rises........which it is doing. Whether it's enough remains to be seen, but obsolete????? Not yet. That is the OPINION of certain japanese manufacturers who would love for two strokes to go away forever because they are now way behind the two stroke technology curve.
Technology curve? you mean KTM's TPI - which is just stick an injector in the transfer stream. 2 strokes will live longest in the RC aircraft and even they are being replaced by electric motors. 2 strokes in toys (offroad bikes) isn't what we're talking about here - I did say mode of transport - and in that respect 2 strokes are fucked.
An 8 track tape is obsolete. A cassette tape is obsolete. Hell, even compact disc is obsolete. We have a long way to go before we can say two stroke is obsolete. It's a bit like AM radio. You wouldn't listen to music on it any longer but it does serve a purpose, therefore, we cannot call it obsolete. I was only responding to your statement in the video that two stroke is obsolete. As long as there is demand and useful applications, manufacturers will find ways to keep on producing them. Not trying to be a troll just trying to explain myself more clearly. You made no mention of modes of transport in your video. You simply stated that two stroke is obsolete. And when I mention the technology curve, I am merely stating that R&D has been done to improve upon the delivery of fuel to the engine. It's not reinventing the wheel but it's a hell of a lot more time and effort put in by the previously mentioned mfgs. than the Japanese have put into it. Aside from possibly Yamaha that amount would be zero. I don't know, I'm getting a little long in the tooth so maybe I'm just more sensitive to words like obsolete. LOL! Thanks for the great videos and keep up the good work!
hi again .ive studied now closely your video and you will be best deleting it. its incorrect ... you insist that its a gas pressure wave in the entire video incorrect . you mention only once that the gas behaves like a sound wave but you never at any point confirm it is a sound wave . you insist that the gasses return to the exhaust port incorrect ....... please go back to wikipedia to further your knowledge or watch someones video who is a genuine professional . best wishes two stoke lover
In kart racing (80's) we saw sliding exhausts, lengthened and locked long by a brake connected cable & pawl when the brakes were applied, released by depressing the throttle to the stop. The pipes we used just had a sliding convergent cone with a locating collar (held by self tappers from outside)within the parallel section. (Between divergent cone and stinger). We could adjust this in the pits whilst experimenting with header length and gearing changes :)
hi, great vid. there is an easier way to adjust the pressure wave in an expansion chamber. the reflected wave is , to some extent governed by the diameter of the outlet to the stinger and this could be adjusted using an "iris" valve , similar to the aperture adjustment on a camera. just a thought, somebody will no doubt kick holes in it, cheers.
Ahh the good old 2 stroke days. Cuttin skirts, filing ports. I miss the smell. Konig had some racing outboards that had a sliding pipe setup on the inlet side of the expansion chamber. Could be slid back and forth with a leaver next to the driver.
What about the properties of sound and mass? That "bang" sound generates frequencies that are bouncing around in that expansion chamber like the exhaust pressure waves are. Unlike the exhaust, it's energy, not mass but requires mass to exist, move. That same dependence for existence (mass) is what will eventually consume it. Both change when contact is made. Mass just bounces off each other but sound frequencies can bounce off of, viberate through or get absorbed by mass depending on the density and composition of the mass and the frequency and volume of the sound.
thanks for the videos your explanations help me to visualize how this works,i once made an expansion chamber exhaust system for my Yamaha rt 180, it actually had 2 power bands first would start to drop off and a shorter one would hit taking it to its final rpm.Sure felt strange but was fun.
Hi Matt, since I bought me a Gogogoped a few Days ago, I stumbled across this Video again. You mentioned a Seal for a very hot and dirty Environment in the Exhaustcamber... why not just use one or two big Pistonrings? Oil should be no real Problem, since in some Cases it pisses out the Endcan anyway and leaves black Marks all over the Exhaust. Cheers Dude.
Hola. i,am argentina. don't understand you to much jajja, so, i thimk that's lovely explane. congratulations. your fonetic voice is very dificult for me. now, what about of resonance of exaut gas? is this one way of Arquimedes inverse efect? i surcribe you colega , greeting
Could You explain (if it's explainable) why 4-strokes don't have such expansion pipes? I guess it's all about the fact You get twice the pressure waves as in 4-stroke, but could You put more light on this?
So what is the benefit of having each cylinder go to its own muffler? I understand seperate expansion chambers but why can/should they not connect up to one muffler after the expansion chambers?
Your getting lost in the physic if the pressure waves and you fail to put it all together as to how the expansion chamber working in conjunction with the powervalve timing & incoming intake track flow rate synchronize to increase the power of the engine at that perfect resonant frequency of the reflected sound waves. Clear as mud. Sum it up already.
Seems like the expansion chamber makes the biggest difference in a two stroke exhaust, is there any benefit of an aftermarket silencer? Seeing as how they all are a perforated tube wrapped in fiberglass? (Speaking for dirt bikes)
What if instead of a separated sliding expansion chamber you used a sliding cone inside the expansion chamber that has a pipe that slides inside the outgoing exhaust. That would eliminate the need for a big seal along with the big pockets of disturbance. Maybe use a rack and pinion type system for adjusting the expansion via the sliding pipe inside the exit pipe, what are your thoughts? Thanks for another great vid
At subsonic flow don't you normally get and increase in pressure in a divergent duct and a decrease in pressure in a convergent duct. Ie increase in velocity = decrease in pressure and decrease in velocity = increase in pressure? Bernoulli principle
Great explanation! If somebody like you have come accross when I was studying engineering I would probably have stayed closer to mechanical engineering. Congrats mate!
Just curious.. some pipes will be more for low end power (fmf fatty), or high end revs, (fmf gnarly). How can they change that (increasing power at different ranges) or is it just the timing of waves at different rpms?
They still use them in the USA Enduro scene......but the numbers are horrible. RLV is the only one that I know of that produces them. Obviously, they make them in very small quantities.
Tunable exhaust is sort of a thing on two stroke jet skis albiet black magic. They have ECWI systems available that electronically inject some of the water from the engine cooling system into the exhaust stream before it diverges in the cone (since it takes water from the lake to cool we have an unlimited supply). Since the wave travels at the speed of sound people tune pipes by injecting extra water at low rpm to cool the pipe slowing the speed of sound down, lengthening the pipe. Tapering the flow back as the pump pressure and rpm increase with electronic solenoids and an MSD brain allows the pipe to heat up as the RPM increases speeding up the sound wave and shortening the effective pipe length. Can you go over some theory on how we could do the tuning better? Where should we be injecting the water in the pipe? Should it be in a fan pattern with a spray bar? Additionally how does a twin cylinder differ to a single cylinder in regards to using one shared pipe. We have an exhaust manifold that allows the cylinder gasses to converge before the expansion chamber, how would that affect the scavenging process? The engine that seems to be the most used in the two stroke circles on the stand up jet skis is a 62t yamaha twin cylinder 701 with a 81x68 bore/stroke. A video would be great on this premise if you have the time. Cheers.
I found this video showing a variable length expansion chamber where the sliding seal was part of the header pipe rather than the belly section. The guy at Allspeeds told me its the best place to put the slider. A colleague at Lotus made a trapping valve design two stroke which closed the exhaust port at precisely the right moment thus doing away with the need for the chamber. I never saw it in action but there are some drawing of it around. Your videos are very good, thanks for uploading them. Here is the video ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-0odVzSgufjk.html
I was thinking why not just have multiple expansion chambers? Obviously for a 4 cylinder this would be impractical but for a single or a twin having a low mid and high powerband Chamber per cylinder seems like a good idea, only thing would be the branch and valve system to control the flow of the exhaust into these chambers. This just seems too simple to have not been used though, but ive never heard anyone or seen any bike that even had a similar concept. Of all the strange engines 2 strokes had tandem twins, square 4's etc this doesn't seem like a huge big brain complex one.
help!, my yz125 has a nasty bog to it (mikuni tmx 38 carb) if im riding in high gear just cruising along, if a slam the throttle all the way down fast the bike bogs, but when i gradually increase the throttle bike pulls fine. Please HELP
Just as a note dont get confused normally the ideal gas law and uncompressible flow would dictate that a divergent nozzle increases pressure but decreases flow and a convergent nozzle would do the opposite. These are the assumptions when designing a nozzle for a rocket engine or most other applications. Here we are dealing with a compressible flow wich is quite a lot harder to simulate and design a nozzle for. In Rocket engines the pressures are so high that compressible flow isnt really a concern, here you would rather consider pressure shockwaves in supersonic flows.
So, if I may ask, I have a stock 75 Yamaha RD250 and it has its stock pipes on it... Since 2 strokes work off pressure waves, how does a relatively straight, baffled exhaust work? Is it the baffles providing the pressure waves? Or is it a simple means to an end without a true performance gain?
It's a simple means to an end, yes. Lots of older 2-strokes have straight pipes with no real expansion chamber simply to keep them less powerful, simpler to manufacture, and more "reliable" due to lessened peak power output.
so on this hypothetical seal for a hot and dirty environment. unless you can get a high temp flexible boot to work on a loose seal, seems to me that (if you don't need a muffler) you make that joint the final exaust port. the simple illustration would be pushing a tin can in and out of a very wide exaust pipe with enough gap to be equivalent to a normal exhaust
there is a pipes for rc trucks like that it has a spring on it to slide it back in place and it works really good makes good power all around I like to make 1 for a bike but I don't like the looks so far from what I made
I enjoy your videos, and am subbed.. But on this particular aspect of two strokes, (and porting) I've had a long acquaintance.. and feel you could have explained things better in different way... that most would understand immediately. For instance, if you'd have used the analogy of sound propagation in air... Sound travels in air in waves, as we all know.. and can be thought of as many waves travelling in concentric circles from the source, (at it's simplest)... And so, it's only a small step to show that the 'leading edge' of the travelling sound wave is the 'high pressure' part of the wave, banging up against normal atmospheric air... and the trailing edge of the sound wave is the lower pressure side.. Which is quite true.. and it can be shown to give a slight vacuum too as it moves along. Just as tailgating a truck 'pulls' you along in the lower pressure envelope behind it. And... just like a pulsing audio speaker beats the air to send it's pressure (sound) waves out... Or... this analogy... concentric circles running across water from the splash... will 'reflect' (like sound will) off any solid, or firm, obstacle, like a boat or a riverbank, say.. these waves will reflect back towards the origin of the splash source if perpendicular to the wave, or glance off at the angle it meets the obstacle. Similarly, the fat 'racing' expansion chamber will have a steeply reducing REAR cone (leading to the end pipe) in order to REFLECT a high(er) pressure wave back towards the exhaust port. Personally, I think it's a bit of a mistake calling this a "rebound"... because a rebound implies that the exhaust gas actually travels backwards, and it doesn't.. (or.. only as much as a ball in calm water does.. when a wave passes by, i.e. it has a slight circular motion then returns to being still). The 'reflected' high pressure wave DOES travel backwards though... and the WAVE FRONT does a great job of putting a wall up against the next exhaust gas rushing straight out of the cylinder.. (But only at a particular and very narrow rev range as you mentioned). The sound analogy is a bit more than an analogy too. Because the exhaust gas wave, the 'expansion' into the can, and the reflection back towards the exhaust port ARE sonic waves! I just think that most folk will soon see the bunching up of the wave as it travels.. and the "rebound" effect... will be more easily understood if you mention sound waves.. Everyone understands a brick wall will reflect sound.. without even thinking about getting their head around molecules compressing together and then stretching apart... Anyway, just my two penn'th.. and thinking out loud. Keep the videos coming! :-)
Cool - and yes I agree. I'm not an expert in analogies and try to break it donw in a way I think works. This is not always the best way (obviously) and this wil be built on. As for trying to get across that exhaust gases don't reverse and its just the pressure that is reflect is also not entirely true. Fresh charge escapes the cylinder and if the pipe is in its rev range then this charge is forced back into the cylinder. Now, I'm totally with you that the exhaust doesn't travel bak and forth but you can understand what I mean here. The aim is to get the initial idea out, then build on it from there. But these comments are great, and will be added to the next video on this subject, which will have some physical deomnstrations - matt
Instead of changing the length of the whole expansion chamber, you could have a move-able internal baffle shaped like the convergent cone. You wouldn't need to worry too much about sealing the outer diameter of the cone, in fact you could leave enough clearance that leakage past the edge could be the flow path to your muffler. moving it fast enough to keep up with acceleration in first gear might be a bit of an issue. A stepper motor and a threaded shaft maybe? It's interesting how snowmobiles got around this problem, they use a CVT transmission that keeps the engine on the pipe instead of a pipe that adjusts to the engine.
like most mopeds. Great idea about an internal cone, the problem comes with having a motor that could survive the environment. As for the first gear problem and second for that matter, you could just ignore them. Have the cone at a set 1st and 2nd setting then move during higher gears where you need it most
I wonder if you could use a liquid seal from something like a sodium (well something more stable, but still point is a metal or alloy that melts at a certain temperature) and then having it wet the surface to form a thin film that acts as the seal. With the right viscosity it seems like the right kind of idea, the nice thing is that when it cools down it becomes a solid piece again so it won't leak on a low throttle setting.
Hiya... You obviously know what you're talking about ... whereas me... naaah! I'm in the process of, let's say, "refurbishing" a Honda Pantheon 125 (FES 125), which is the 2-stroke version from pre 2003 (it's a year 2000). It had been sat for 10 years outside, so there's a few things that are worse for wear on it, however, making good headway and surprisingly there are still some useful OEM parts available. However, I'm looking to "beef it up" a bit and fit a Malossi Clutch set up and Final Drive gear for example, but I was also entertaining the idea of refitting a Polini Carb and Air Filter. I don't want to refit the original Honda exhaust back on it, though. For one, it's rusty as hell and yes I could clean it up and repaint it etc. but I wanted to fit a sports orientated or aftermarket exhaust to offer a little bit more power to the bike and to improve the aesthetics (the Honda exhaust is pretty ugly). I've been all over the internet for 2 days looking for an aftermarket exhaust for it and can't find any manufacturer that has stock or even lists one! So, I've been contemplating, cutting off the Muffler from the OEM part and welding another 2-stroke exhaust unit to the pipe. It was that idea that brought me to RU-vid and obviously to your very informative video, which has now made me think that I could mess up the whole optimum output by doing that. How much of an impact would it have, if I took a pot-luck shot at locating a random 2-stroke expansion and end can and fitted it to my scooter. What's the worst that could happen? I would really appreciate your advice, thank you. Curt
Bad idea to just randomly slap exahusts onto your engine and hope it works. If you have the time and patience, you can figure out your port timings, cylinder volume (125cc) and other factors and use a free pipe design software to calculate the most effective pipe design for your engine and desired peak power point and powerband width, and then measure diameters and lengths until you find something reasonably close.
