Another Carburetor Question ?

Hi ! I have a 1982 Yamaha xj650j maxim that I've been trying to diagnose a pesky carburetor issue. I would welcome any help from the experts on this forum. The issue is with a extremely lean condition on 3 of the 4 plugs following a plug chop. I have adjusted the air mixture screws out to at least 5 turns and still don't get an improvement to the lean condition. Could the float level be too low ? I have removed the fuel bowls and thoroughly cleaned the small passages and they were all slightly to totally blocked. The carburetors were supposed to have been rebuilt by Peoria cycle according to the previous owner and when I installed them on the bike it ran pretty good but as time went on it seemed to run too lean on 3 of the cylinders and adjusting doesn't get a response. Is there anything that could have been done wrong in the rebuilding process that could create this issue ? The bike idles great and is very responsive ! THANKS ------- DON

 

Re: Another Carburator Question ?

Get them pilot mixture screws back to 2 3/4 turns out to start.
You can check your float levels with the carbs on the bike, short piece of clear tube on the drain, if they are out you will have to pull the rack.
Also the main & pilot air jets can get switched, it should be: main (large) pilot (small) threaded hole for baffle plate (may or may not be fitted)
The screen filters can also be missed when cleaning.

 

If you are running lean on one cylinder you most likely have an air intake issue on that particular cylinder. I had a similar problem on my xj once. I tried to colortune it and could not get a any change on one cylinder. Once I sealed up the carb boot on that one cylinder I got a noticable change in mixture. Check for leaks on that one cylinder and that may correct the problem.