Running Rich. About to drive me crazy. Please Help! - ATV Forum - All Terrain Vehicle discussion for Honda, Yamaha and more ATVs
 
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post #1 of 1 (permalink) Old 05-11-2019, 12:18 AM Thread Starter
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Join Date: May 2019
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Running Rich. About to drive me crazy. Please Help!

I have a 2003 Kodiak 450 i recently acquired with a carburetor full of jelly which was causing it to bog down outside of idle. I partially rebuilt the carb by adding a new needle valve/seat and replacing o-rings with a thorough cleaning. It runs very well outside of idle, the idle itself is a little choppy but it doesn't cut off or anything like that. No bogging on acceleration and throttle response is good. The old plug was fouled up and black as soot (dry) so i replaced it with a new one. Within 15 minutes of riding the brand new plug looked just like the old one. I have cleaned the plug multiple times in order to test it after I took the carb off to adjust a few things, and I can't seem to improve it no matter what i do. I'll list a few noteworthy things below. Any help would be greatly appreciated as I am at my wits end.

Mikuni BSR33 Carb
- Starts right up cold with no choke applied.
- Is a little harder to start when hot, but will run.
- Adjusted float to service manual specifications (13mm)
- Fuel mixture screw can be screwed all the way in, and the 4 wheeler won't shut off.
- I have noticed a minimal difference from 0 turns all the way out to 2.5 full turns of the fuel mixture screw.
- All jets are stock including the pilot jet (17.5)
- Needle valve and o ring have been tested and are not leaking
- Exhaust fumes are strong at idle but not black
- Air Filter is brand new

Other thoughts
-I have read that this may point the pilot jet being too large, but is it normal to have to downsize from factory OEM?
-Could the float height need more adjustment? Which would throw it out of the range that the service manual says.
-Judging by the old plug this was a pre-existing issue prior to the carb getting gummed up. I'm guessing it was just run rich by the previous owner since you wouldn't know it outside of the somewhat choppy idle without looking at the plug.
-Another thing i noticed was on startup it runs at a slightly high rpm for around 30-45 seconds (around 2200) before settling down to the normal 1500 rpm area.
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