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Hey I got gas leaking back through my airfilter. I thought that it might be poorly adjusted floats on my 1983 Yamaha 400xs. I had bought a set of carbs from a junk yard and replaced any part that was in better condition that what I now had. This included the floats. So I put the old ones back fully expecting this to solv my problem. However no luck after a trip around the block I was leaving a trail of gas again.


Any ideas?

Does that mean that you adjusted the floats or just replaced them with different ones?

well initially I replaced them. Not so much because I needed to but because I could . Well when gas started to pour out of my bike I thought I should go back to the way it was. When I knew the floats were properly adjusted.

I did notice that the rubber intake tubes aren't so plyable and I can't get a good seal between the intake box and the carbs. Also I was told I needed new manifolds between the carbs and the engine. I don't see any cracks and there seems to be a good seal but I'm sure it couldn't hurt.

Could the hard rubber tubes (joints) cause a vacuum back out the other way?

if you didnt replace the rubber o ring on the float needle seat this is probably where the gas is coming from.the o ring dries out and lets gas leak past it even though the needle has cut off the flow of gas through the seat.as for the intake rubbers take them and clean them good with soap and water and spray some Plasti-Dip on them this will seal them.yamaha dont sell the needle seat o ring separately but you can get one at any auto parts store that has a metric o ring selection.