Pefromance Exhaust

Discussion in 'Performance Mods' started by kcpoloman, Feb 5, 2009.

  1. kcpoloman

    kcpoloman Member

    Whats up everyone? I'm still new this motored bike thing and I am trying to find a good performance exhaust for my 80cc. I have looked but just cant seem to find anything and honestly, I dont know what kind of exhaust to look for.

    I am wanting more top speed. I plan on getting a 36tooth sprocket along with a new exhaust. I have heard something about expansion chamber exhuast but I am not quite sure how they work and how much more power to expect from one.

    Anytips you guys have would be great or just point me in the right direction of a good vendor.

  2. cooltoy

    cooltoy Member

    I know there are at least two or three out there. Try searching in the white zone, you will see a post from Ghost0
  3. Ebay look for pocket bike exhausts.I got one for a pocket bike that is straight gonna have to cut the end and remake the curve to the engine. Not sure i can use this style yet but it was under 30 bucks so i thought id try it. Ive had really good luck and power too from just opening the pipe i had and cutting off the tube coming off the bottom piece going up into pipe. I cut it off flush and put it on the third notch on the carb needle and then opened up the air intake box to make it look like its frowning lol..really woke it up and was able to pass my buddies . Something in something out,has to work as a team.
  4. fastboy9

    fastboy9 Member

    If you've got a bit of money to spare then look for a kawasaki kx65 expansion chamber (all 2 stroke performance exhausts are expansion chambers) your "80cc" is actually 67cc so that exhaust wouuld be tuned more to the engine. Expansion chambers are tuned to the engine size, they are made in three sections. The divergent section is the first bit after the header pipe, this is an opening cone, here the gases are sped up, then they go into the middle section, here the gases expand. Next they will enter the convergent section, this is a cone (big to small) where they will bounce back causing backpressure which will keep the fuel in the cylinder, stopping it from sliding straight over the piston and back out of the engine. The end result is a sucking action that pulls the fuel into the engine faster, having similiar effects to a turbo or other forms of forced induction. The dimensions for the different sections of the exhaust have to be the right measurements to be tuned to the engines size. So you cant just put on any old exhaust. Here is a good animated diagram that explains the function pretty well:

    I have put a pocket bike exhaust (tuned to 49cc) on my 59cc (60cc happy time) engine and it works quite well, I have the same one as Ghost0, heres the thread:

    What I would recommend is to buy a pocketbike exhaust, it is possible to tune it as close as possible to your engine, this is all done by the header length, the pipe from the engine to the expansion chamber. The length will determine where the powerband (where there is an increase of torque at a certain rpm range). The shorter the header pipe the higher in the rpm range the powerband will be (more top speed) the longer the header pipe the better low end torque (faster acceleration).

    You can experiment the header length by using a silicone tube and hose clamps, by pushing the metal pipe on the exhaust pipe into the silicon pipe further you will increase your top end. This is how you will tune your exhaust to your engine, once it is tuned how you want it you measure the header length and weld up a pipe for it (brazing copper tubing can also be used). Ghost0 found the optimum header length to be 12 1/2 inches for that particular pipe. I would start from there and start shortening it until you are happy.

    The sound is a lot deeper and alot like a dirtbike and the pull is so much nicer! Most 2 stroke tuners will agree that 45% of the engines power potential is in the exhaust design.

    Sorry about the long post but I hope it will give you an insight into 2 stroke performance exhausts.

    AndyInchVille of Kings sprockets was manufacturing tuned pipes for the happy time engine, and Santa Cruz Scootwer Works (SCSW) pipelyne in san jose were making them too. Theres a thread in the 2 stroke engine section with both Andy and a guy from SCSW offering them: to be honest if I had the moeny I would get a ready tuned one, will look much cleaner, save a lot of hassle and will be more powerful.

    I definetely recommend it :)

    Last edited: Feb 6, 2009
  5. Thanks for the info ,i just might put more effort into getting my exhaust put on then if it helps that much. I bought a straight pipe instead of the curved one and its long so its gonna be fun to try to get to work lol
  6. golden_boy

    golden_boy New Member

    I just bought a used kx 65 expansion chamber for $15 on ebay. I think I will have to wait to install it when its a little warmer outside...booo. I've heard they work pretty well with the "80cc" engines. I will give a detailed review when I test it in the spring (or sooner if I get impatient!).
  7. kcpoloman

    kcpoloman Member

    Thanks alot Fastboy. Very good post. You answered the questions I had. Thanks for taking the time to type that all up.:2thumbsup:
  8. fastboy9

    fastboy9 Member

    No problem! I just want to see more faster bikes out there! All the other explanations I found were a bit confusing so I hope that was easier to understand.

    Good luck

  9. zackwyldefan

    zackwyldefan Member

    one wuick question. if the exhaust (stock) is placed in a way that it shoots straight up, would the engine still run? or would it have any effects?
  10. cooltoy

    cooltoy Member

    That was good Fastboy
    It all makes sense now.
    No Zack, it should not make any difference because the engine will not know. I guess rain could be an issue:jester:
  11. zackwyldefan

    zackwyldefan Member

    thanks cool toy you saved me 65 bucks that i would have spend on the exhaust from still need their clam shell for my chopper hopper.