A new carb problem (corrected)

[joneruss]

M/C is a 1991 GS500. When the bike is at idle, 1.3K to 1.4K RPM and I remove the spark plug cap of the right cylinder spark plug the engine immediately dies. If I remove the left cylinder spark plug cap, the engine keeps running.

If I adjust the RPM at idle to between 2.0K - 3.0k and redo the test, the engine keeps running at about 1.2K RPM whichever spark plug cap is removed.

Looking at the diagram here: http://www.kawtriple.com/mraxl/carb/mikunicircuit.html
of the mikuni carb circuit, it appears, to me anyway, that a blockage of the right left pilot jet could cause this problem.

The engine is stock and I recently removed the covers of the pilot screws and set them about 2.75 turns out. I also have one washer on the needle but looking at the referenced diagram, I don't see that as being a part of the problem.

When I blip the throttle the engine revs freely to about 5.0K - 5.5K RPM; and again based on the diagram, the impact of the pilot jet is now minimal at that RPM.

I have difficulty starting the engine but after a few brief runs, it will stay running (on one cylinder???). When I do get the engine started with full choke on, the RPM rarely goes over 1.6k RPM.

I've check the float levels, swapped spark plug sides, and sprayed the carb boots with WD40. Have not checked the valve clearance; that was going to be a winter job.

I lost the O ring under one of the carb diaphragm covers, and replaced it with an O ring of a slightly larger size. Could that be the problem? That would be an easy fix.

Does anyone agree with me on the cause of the problem or have suggestions on what the problem is?


Thanks,
J

[Paulcet]

[color= black]Looking at the diagram here: http://www.kawtriple.com/mraxl/carb/mikunicircuit.html
of the mikuni carb circuit, it appears, to me anyway, that a blockage of the right pilot jet could cause this problem.
J[/color]

That's a good diagnosis.  I had the same situation. Get in there and clean the jet.

[the mole]

I think you'll find its the left idle jet that's blocked, because if you remove the right plug lead, it dies. That means it was only running on the right one. If you remove the left lead it keeps running, because the left cylinder wasn't firing at idle anyway, so that's the one with the blockage!