1990 Big Bear 350 running very rich - Yamaha ATV Forum
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post #1 of 3 Old 08-25-2018, 01:10 PM Thread Starter
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Join Date: Apr 2015
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Hey guys, I’m stumped on this project big bear I picked up from a co-worker. I’ve got it to the point where it will finally idle but still rough, give it throttle and it’s sluggish and kind of that hitting rev limiter type sound, still blows a little black smoke, has no air filter on currently and if I put my hand in front of the carburetor it gets soaked in gas. Gas is not overflowing, taking the muffler off does not make much of a difference.

So far it has a carb kit installed, float adjusted correctly, fuel needle and seat work perfectly, needle clip setting is on the highest notch, mixture screw is at 1 1/2 turns.

New NGK D8ea plug, new coil, nice blue spark finally. Valve clearance is good, 130 p.s.i compression. Any tips on what to check next?

Last edited by goofy3392; 08-25-2018 at 01:40 PM.
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post #2 of 3 Old 08-26-2018, 12:41 PM Thread Starter
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Problem solved. The main jet holder/jet tower is plastic and has 2 o rings, those o rings were destroyed. To remove the jet holder you have to take out the 2 torx screws from the inside by the throttle slide. They are square cut o rings. These parts are not shown on the parts diagrams or micro fiche.
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post #3 of 3 Old 08-27-2018, 10:39 AM
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nice find
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