chuckles_no Posted July 17, 2009 Share Posted July 17, 2009 I just cleaned, rebuilt, and synchronized the carbs for my xj550. Whoever got their hands into those carbs, previously did a real dandy. The air/fuel mixture screw seals were already drilled out and reset to... get this... #1 carb was 3 turns out, #2 and #3 were 3 1/2 turns out, and the #4 was 2 1/2 turns out. I almost never mess with the manufacturer setting on those and just gave a wild guess on how many turns and know I am way off. I have them all turned 3 turns out. But it is running rich and my RPMs hang bad around 3000. They are cleaned and rebuilt now, and balanced. Idles and runs nice all except for the rpms hanging high. No air or vacuum leaks at all. Does anybody know the setting for the xj550? and if they were equipped with afterstock, larger jets, should it be set to less than stock or more. By "more or less" I mean screw turns. In should be lean and out should be rich. Link to comment Share on other sites More sharing options...
ltdave Posted July 18, 2009 Share Posted July 18, 2009 factory settings were 2-3/4 turns from fully seated (closed)... if they are NOT original sized jets, then the procedure is to close them all and start with #1. if you suspect it is too large, then start with it nearly closed. crank the starter while slowly turning the mixture screw out. once it starts and runs, then add #2, then 3 and 4... after youve done all that and it continues to run, a color tune plug will help get a lot closer. another method for fine tuning is to do plug chops. get the engine up to operating temperature by running it on the street, come back to the garage, rev the engine up to several thousand steady RPM the hitting the kill switch while under throttle. pull the plugs (keep them in order) and give them a good look. clean white is lean, black sooty is rich. a light toasted marshmallow tan is just about right. if you want a little bit smoother ride you can run it slightly (VERY!) rich but according to another tuner, the razor edge of performance will be achieved by nearly too lean. it will give you good engine braking when you close the throttle... MAKE SURE your valves are properly shimmed and the carbs are bench sync'd before starting... Link to comment Share on other sites More sharing options...
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