1980 Yamaha Carb Problem

[aragoth86]

I have a 1980 Yamaha Midnight Special XS 850. It is leaking gas from the air intake on the leftmost carb. i just rebuilt all three. anyone know why this is leaking?

*edit*
I forgot to mention that it only leaks when turned off. it doesn't leak when it's running

[UncleBob]

Originally Posted by aragoth86

I have a 1980 Yamaha Midnight Special XS 850. It is leaking gas from the air intake on the leftmost carb. i just rebuilt all three. anyone know why this is leaking?

*edit*
I forgot to mention that it only leaks when turned off. it doesn't leak when it's running

there are two problems here. One, the petcock is leaking (I'm assuming its a vacuum operated petcock...if I'm wrong, disregard) the other problem is you have a leaking float valve.

Unfortunately, that means your carb "rebuild" didn't take. If you paid a shop to do the rebuild, I'd definitely take it back. There is a couple things that can cause this. Sometimes its simply a sticking float/valve that a light tap with a screwdriver handle will solve, sometimes its sediment from the tank contaminating the seal of the float valve (tank rust for example), and sometimes its the sealing surface itself is sub-optimal....but whichever it is, it needs to be torn down again, inspected and fixed.

BTW, even though you might not notice a problem while the bike is running, its leaking then too.....that cylinder is probably running richer than it should at idle.