I have a 1979 Yamaha GT80 that I recently got running, but very poorly. I have rebuilt the carburetor and decoked the top end. It is hard to start and once started, will not idle. When giving it throttle and then releasing the throttle the rpms take a long time to slow down. There are two small hoses on the carb, but I can't see where they are supposed to connect. Are they both just overflows or vent hoses? Can anyone help? Thanks.

I have a 1979 Yamaha GT80 that I recently got running, but very poorly. I have rebuilt the carburetor and decoked the top end. It is hard to start and once started, will not idle. When giving it throttle and then releasing the throttle the rpms take a long time to slow down. There are two small hoses on the carb, but I can't see where they are supposed to connect. Are they both just overflows or vent hoses? Can anyone help? Thanks.

You have an air leak.

To solve this, spray the intake, head and base gasket down one at a time with brake cleaner...if the revs increase, you found your leak. If that fails, it could be your magneto side crank seal, but don't spray anything there.

Threebond 1194/yamabond can be used in a pinch to seal the base gasket. Note how I said IN A PINCH...if you can get 1mm gasket paper, use that.

Holes on the carb...one vent, one overflow, the oil injection goes into the top of the reed valve intake...make sure that hole is not open, or else you will have a leak.

Any specific photos needed, just ask, but QUICK! I have this bike, but am going to sell it very soon.

Thanks for the reply. I checked all the areas you suggested (eg. new base gasket, etc.), except for the crankcase seal. Thats likely the problem.

Dan