I have a '76 Yamaha TT500 I'm trying to restore and the exhaust pipe had no muffler on it which it stopped just past the foot pegs so I had a old Honda XR100 exhaust that i robbed the muffler from and added it to the TT500 and now it won't start, could it be to much back pressure?

Budman 362
:bonk:

Well, take the muffler back off and see if it will start, and you'll have your answer.

I'm sure the silencer for a 100cc engine has much too small an internal diameter for a 500cc engine. I remember the XR100 I had as having an exhaust outlet about the size of my pinky.

Well i let it sit for 2 days and had my mind made up to cut it back off but I tried it again and on the 4th kick it started and ran great so the XR100 wasn't too much muffler after all maybe it just needs a tune up. I did check the outlet of the muffler and it measures 1inch.