Air blowing out vaccum

[snateman]

I have a 1978 XS1100 that ran perfect when i put it away two yrs ago. When I pulled it out of storage it seems that the #4 cylinder is not working properly. At idle up to 3000 or 4000 rpm it misses on #4, once the rpm's get up there it runs fine. When running at the lower rpm's air blows out the vacuum on the carb boot. I have cleaned the carb. Any help would be greatly appreciated.

[DGXSER]

I know this will soud impossible from the view point it ran fine when you put it away and did nothing in between, but this sounds very much like a stuck or bent valve to me.

Once you get into the upper RPMs on these bikes a miss seems to disappear, even when it is still there. And I have worked on one with the same issue that we found to be a bent valve. Run a compression check at least, just for S&Gs.

[dbeardslee]

Did it have gas in it while it was stored?

[snateman]

It did have gas in when stored.

[dbeardslee]

If gas has been sitting in the bowls for two years, chances are it's got the carbs gummed up. Usually it's worst in the bottom of the bowls, and you need to make sure the little jets in the bottom of the bowls are clear. Sounds like a job for a can of carb cleaner and a bread tie.