Some questions about a carb float issue

[anthonywanderedaway]

Hey all, this is my first post here, thanks for having such a great resource for xs650's!

I recently bought a '78 650 Special and have been happily riding for about a week now. The other day I went on an 80-mile ride with no issues, but on the very last mile before I got home, the right cylinder began to cut out and I barely made it home. Lots of gas was was leaking from the airbox and the plug was wet with gas also.

Some forum searches led me to diagnose it as a stuck carb float causing the float bowl to overflow. I removed the float bowl and float, checked that the float didn't have any leaks, and reinstalled the float bowl.

Tried starting, same issue with gas in the airbox.

Would adjusting float level be the next step? I initially didn't go that route because the problem popped up suddenly and it didn't make sense to me that the metal float tang would suddenly go out of adjustment so radically.

Are there any other possible causes for this problem?

The petcock on that side is also leaking some gas. Would a faulty petcock lead to this problem as well?

By the way, the bike has the stock BS38 carbs and vacuum petcocks.

Thanks in advance for helping!

 

[xjwmx]

You have two separate problems. The leaky petcock isn't causing this carb leak. Besides float level or hanging float, you can have a float needle and seat that doesn't seal. They can be cleaned up or replaced. BS34 years can have a leaky seat o-ring.

 

[anthonywanderedaway]

Thanks for the help. I took out the float needle and float needle seat and found a little piece of black rubber that had somehow worked its way into the float needle seat, and I guess it was impeding the needle from making a seal to stop the flow of gas into the bowl.

 

[xjwmx]

That should fix that. Now you probably want to figure out why the petcock is leaking.

 

[xjwmx]

People say the clear gas line tubing is less inclined to shed pieces that end up in the carb. You can get it in the lawnmower section of any auto parts store. 1/4" size. Also, get the smallest lawn mower 1/4" gas filter there and stick it in the line.