problem with expansion chamber

[gohst ryda]

hi i have a stock 67cc motor and i have put on a moded expansion chamber, the pipe to the chamber is 12inch long and then i have atatched the stock muffler end onto the expansion chamber.
the bike now runs very torqie at low speed but at mid top too top end it want to slow down and seems like it is starving of either fuel or air.
it also seems to really over rev and is louder then expected at top speed. i dont run it long at top speed i pull in the clutch and roll where possible
an anyone help with any of this and to also get it quieter.??????/

 

[Ghost0]

Check your plug and see if it is running too rich or too lean, either can be causing it to not run right at higher rpm's. I had to lean mine out a lot when I put my expansion chamber on.

 

[gohst ryda]

how do you do that???
im not sure how to get more top end

 

[Ghost0]

The color of you plug will tell you if you are running too rich or too lean, white is too lean and black is too rich. You can adjust this a little by adjusting the needle in the carb my moving the clip up or down. If that is not enough you will need to get a different jet.

 

[gohst ryda]

how do you move the needle ??? i cant seem to find what ur talkn bout????

 

[Ghost0]

The needle is attached to slide in your carb that your throttle cable attaches to. The needle has 4 slots in it where an e-clip goes. By raising the e-clip closer to the top of the needle it will lower the pin allowing less fuel into the engine. If you lower the clip it will raise the needle allowing more fuel into the engine. It has the greatest effect at low to mid throttle so if you still don't get the desired effect you may need to get a different jet