Can't figure out gas in oil


XS400 Addict
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Portland OR
I've read lots of posts on this. I have gotten my bike to the point where it is running great but after I ride a couple miles I get gas in the oil. It does not seem to be leaking into air filters and it's not the petcock leaking because I have installed an inline fuel cut off valve. I've read it could be leaking past the piston rings if they are bad? There is no smoke and bike idles well and runs well until it gets to full with gas and dies. (Happened once,changed oil, installed cutoff, checked oil before I left my house looked right smelled right, got to work 2.5mi and it is full in the sight glass and smells very gassy).

Maybe to help the poster...

If the float needles/valve are sticking open... where would it leak (I'm curious as well)?
like would the gas be going upwards,
and then out of the needle jet into the main carb body area...
and into the air filter area,
and into the breather tube,
and into the bottom of the engine?

and I guess it could go upwards,
then get into the carb body,
then into the carb intake,
into the engine (into the cylinder),
then past the piston rings?

Does that sound correct?
I'm curious as well on the paths into the engine.

My problem was two of my fuel-cut-offs (well ... 2 manual petcocks really) stopped working the 3rd year I had a new fiberglass tank. Now have my old tank back on and its working swell.

P.S. could this also happen if incorrect float height is set (like while having the carb upside-down, set the float height too small maybe?)?
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Thank you for the replies. I'm glad to hear it might not be the rings. I will look right into the floats/needles

I would really like to know the paths into the crankcase as well. What causes the floats to stick? Is there a way to test if the floats/needles are working before putting the carbs back on? I've ridden the bike 5 times and have done 4 oil changes... Getting kinda pricey :banghead:
With the carbs off and upside down (no gas in them:wink2:) with your mouth blow into the fuel barb. They should not let air flow. This will tell you if they will seal. But will not tell you if the float level is correct. That would still need to be adjusted if off.
That's for bikes that don't have the barbs on the bowls. For setting my floats I just measure them with the bowls off with a small ruler. Making sure you petcock is not flowing fuel when it's off and a new set of float valves ( with the floats set to spec) is anyone's best bet for stopping fuel from getting in the case:wink2: