Cylinder 4 is running rich

[Guest]

My 1982 GS550L trike. Stock airbox, stock jetting, Harley mufflers, great spark. Cylinders 1,2,3, have a nice tan plug. Cylinder 4 is black and running rich, you can smell it. Stumbles a hair at low rpm, and stumbles alot at around 6,000 rpm or so. 1,500- about 5,000 rpm it runs crisp. It seems like cylinder 4 cuts out at a high rpm. Carbs are clean. It has the rubber grommets on the pilot jets. Could possibly a leaky grommet on that cylinder cause a rich condition. Adjusting the air screw on the carb has no effect. Any other ideas? Clogged pilot jet? Cylinders, 1,2,3 are perfect. Its just cylinder 4.

-Matt

[BlackStar]

If it has been running OK then all the sudden starts this, my 1st guess would be a fouled needle and seat which would allow the fuel level to be too high. Do you have any fuel dripping from your vents or overflows. Could also be a clogged bleed air jet in the intake bell of the carb or any of the other bleed passages including the air screw passages. Not familiar with rubber gromets on pilot jets. A clogged pilot jet has usually caused a lean condition for me.

[chef1366]

A stuck slide possibly? Or a bad slide diaphragm.

[Tarbash 27]

Well its been doing this since I got the bike. Not leaking any gas, Im pretty sure the float needle seals good. I was thinking of a bad diaphragm and slide too. They seemed fine with the carbs off the bike. But I think I will check it tuesday when Im off work.

[BlackStar]

Sorry didn't realize you had CV carbs. That thing nust be scary fast!!

[Tarbash 27]

Well I was doing 80 mph the other day on it. Hopefully when I get this carb tuned right, it will go faster.

[anikmankar]

solved ?

has this been solved. I am facing similar issues....

Need to check the float height but last i checked it was ok.

Only the 4th one is black and sooty (but not wet)