2-Stroke Exhaust Question

Right place for this I hope!?

I picked up a 1976 Kawasaki KE100 Enduro in a series of trades I made over good ol' Craigslist and I liked the thing, so I decided that I would restore it to look like it once did and hang onto it... In 8 months times I ended up chopping it, slamming it, painting it and decided on making it a street only bike.

Almost done!

It is a 2-stroke however and one of the final components I need is an exhaust. I never really liked 2-stroke exhausts... Expansion chambers were always ugly and they never appealed to me. Question is, can I throw a straight pipe on this bike? I've read that older style 2-strokes had straight pipes and that it would work, I'm just unsure. Single cylinder bike and the stock exhaust is almost straight in itself, but does appear to have a smaller expansion chamber.. It's only a 100cc 2-stroke...

I know it might be louder (and obviously smokey), but I might throw a muffler on the back end that in itself might serve as an expansion chamber. Only reason I bring this up is because this bike has never had a title issued to it, so I'm in the process of getting one. Part of that process is getting it passed an inspection by a police officer. One of the boxes on the inspection form reads "Exhaust System (Good working order, no excessive noise or annoying smoke)"... Let's just hope I get an officer that understands a 2 stroke.... Could always start my quad (4 stroke) that basically has a straight pipe and a muffler next to it to show that 2-strokes really do smoke on purpose lol

Shane

Google "the Two Stroke Tuning Handbook" by Gordon Jennings. All the answers you seek.

I may be wrong but i think a rotary valve motor should run with out any pipe at all so a staight pipe wouldnt hurt any thing, but it would be a pig.Why dont you just run the stock pipe kawwasuckee spent alont of money to design it....it should work and the noise level will never be less

Pssh.. Expansion chambers are ugly... I don't know where to start.

JohnGoFast said:

Pssh.. Expansion chambers are ugly... I don't know where to start.

Click to expand...

The stock pipe goes up and to the left of the bike. It ends up at around my waste. I want my new exhaust to be down, to the right and under my foot peg, like a traditional motorcycle.

Shane

It might seem like a lot, but if you care about how this bike runs and performs, read the expansion chamber section of the manual Yinzer suggested.

http://www.amrca.com/tech/tuners.pdf

JohnGoFast said:

It might seem like a lot, but if you care about how this bike runs and performs, read the expansion chamber section of the manual Yinzer suggested.

http://www.amrca.com/tech/tuners.pdf

Click to expand...

Being that it is only a 100cc bike, I don't really care about top end. The bike will be used for 20 mile trips, maximum... and that is both ways lol..

I would like it to run well though, at least be peppy low end.

Shane

get the street version 100 kawi pipe and muffler
same engine was used in a street bike
or a down pipe expansion chamber with a good silencer
look up centurion kawsaki



after all was suggested ,if you still are considering a straight pipe : put down the CRACK pipe ;D,
go outside and hit yourself in the face with a brick 'till the dumb goes away

xb33bsa said:

get the street version 100 kawi pipe and muffler
same engine was used in a street bike
or a down pipe expansion chamber with a good silencer
look up centurion kawsaki



after all was suggested ,if you still are considering a straight pipe : put down the CRACK pipe ;D,
go outside and hit yourself in the face with a brick 'till the dumb goes away

Click to expand...

Hahaha... This is my first 2-stroke, all my ideas are there, just can't always put together the pieces.

I also wasn't sure if a cone muffler at the end would act as an expansion chamber. Just a solid straight piece of pipe bent to the shape I wanted wasn't really the main idea.

I don't like the stock exhaust at all. It doesn't go where I want it to. It rides up high and on the left side of the bike when I want my exhaust down low and on my left.

Shane

Yeah, you'll want at least a stock pipe on there. The Kawi 100 made 10-12 hp stock, with a straight pipe 5 maybe if you are lucky???
If you can't embrace an expansion chamber, I suggest you trade it for a diesel.

Btw The later model 100's 5 port cylinder compared to 3 port cylinder have a 5 deg difference in the exhaust exit angle.
So if you use an earlier pipe on your motor it will interfere with the frame.

Walms said:

Yeah, you'll want at least a stock pipe on there. The Kawi 100 made 10-12 hp stock, with a straight pipe 5 maybe if you are lucky???
If you can't embrace an expansion chamber, I suggest you trade it for a diesel.

Btw The later model 100's 5 port cylinder compared to 3 port cylinder have a 5 deg difference in the exhaust exit angle.
So if you use an earlier pipe on your motor it will interfere with the frame.

Click to expand...

Any stock pipe won't really work for me anymore. I've modified the bike quite a bit. Plus the look of a stock pipe doesn't go with the style of bike itself as it looks far from what it used to.

My only resort is a custom pipe, which I'm fine with!

Would a cone pipe at the end of my custom exhaust work as an expansion chamber? The cone would be as wide as the old stock exhaust.. Only difference is that I wouldn't have a piece of pipe after the cone, the cone would have an exit and that would be the end. It would be similar to the one picture below.



Shane

no that wont work as an expansion chamber
an expansion chamber has a very specific design
read up on the subject
here is a possible good solution
http://www.ebay.com/itm/75-Kawasaki-GA-3-GA3-G3SSE-G-3-G3-SSE-90-100-muffler-pipe-exhaust-/261035840774?pt=Motorcycles_Parts_Accessories&hash=item3cc6f2d506&vxp=mtr

This is a 4 stroke exhaust pictured above.
There are allot of factors to consider with a 2 stroke exhaust. The rear baffle cone reverse the sound wave so essentially stuffs the charge back into the combustion chamber. It's like a passive supercharger. Even if you only get the length wrong, the motor just won't make power as it should.
If you want to design your own, I suggest A. Graham Bell's book, Gordon Jenning's book or maybe even just purchase 2stroke wizard pipe software. All 3 are cheap

What if I cut the expansion chamber out from the old exhaust and weld the pipe up the way I want, would that work? Or would I have to worry about the total length of the exhaust?

I would use the same pipe diameter, only difference is that instead of the exhaust sitting high and on the left side, it would be under my right side. I'd also try to make it the same length.

Going to take some measuring on my end.

Shane

yeah but keep the headpipe length the same as it was ,same diameter as well
the length is very important for the timing of the sound pressure wave

xb33bsa said:

yeah but keep the headpipe length the same as it was ,same diameter as well
the length is very important for the timing of the sound pressure wave

Click to expand...

By head pipe, I'm assuming you mean the pipe or piece of the pipe that comes off of the head and goes to the cyclinder.

If that is the case, then I think I might be okay and I should be able to make it work with some creativity. Wasn't exactly ideal, but I'll make it work.

What about the size and length of the pipe AFTER the expansion chamber. Does that matter at all?

Shane

just try to keep all of the lengths and diameters as close to same as you can
the outlet end has more to do with noise than power on the stock exhaust

To give you an idea of how the length effects the pipe, the first photo is a pipe made for the Kawi 100 and the peak power was about 11k, we added a 4" section to the header pipe and the peak power dropped to 9k.

bradj said:

I may be wrong but i think a rotary valve motor should run with out any pipe at all so a staight pipe wouldnt hurt any thing, but it would be a pig.Why dont you just run the stock pipe kawwasuckee spent alont of money to design it....it should work and the noise level will never be less

Click to expand...

Is there truth to this? My motor is in fact a rotary valve motor.

Shane

he is shitting you ,I THINK he knows bettr perhaps knot :
an expansion chamber relates almost entirely to exhaust port timing no matter what kind of intake the only thing different about a rotary valve motor is they are a very efficient design compared to a piston port and capable of higher output