crf150r jetting/carb issue....

TeamPropainTurbo38t
Edited Date/Time 3/8/2012 3:51pm
My buddy bought a leftover 09 crf150r last June.....the bike rips but it is a stubborn bitch to start. It runs like crap when cold and when I twist the throttle it seems like the bottom end is "fat".....it hesitates or stalls when u twist the throttle fast from low rpm. Assuming the needle needs to be dropped a clip but what else would make it run this crappy? I took all the jets out and made sure they were clean and I checked the valve clearance. All in spec....
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xnationalwrench 3/7/2012 6:07pm
3/7/2012 6:07pm
Double check the slow speed jet for blockage (hold it up and look thru it like a telescope and see thru it cleanly and clearly). You might also try adjusting the air mixture screw.
mxtech1
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mxtech1 3/8/2012 5:22am
3/8/2012 5:22am
Those bikes before 2010 had poor low speed jetting. You typically need to change the pilot jet and air mixture screw to get it to run better. I usually also lean the main jet at least 1 size. Smaller engines mean more finicky tuning, so it takes a little bit more patience than a big bike. It is a good carb though and runs great with proper jetting.

Just so you aren't overlooking anything, make sure you have fresh fuel, a clean carb (jets and passages), clean air filter, and a fresh spark plug.
CamP
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CamP 3/8/2012 3:51pm
3/8/2012 3:51pm
TeamPropainTurbo38t wrote:
My buddy bought a leftover 09 crf150r last June.....the bike rips but it is a stubborn bitch to start. It runs like crap when cold and...
My buddy bought a leftover 09 crf150r last June.....the bike rips but it is a stubborn bitch to start. It runs like crap when cold and when I twist the throttle it seems like the bottom end is "fat".....it hesitates or stalls when u twist the throttle fast from low rpm. Assuming the needle needs to be dropped a clip but what else would make it run this crappy? I took all the jets out and made sure they were clean and I checked the valve clearance. All in spec....
A 45 pilot jet and the fuel screw at 2 turns out will help starting and low end response. Use a smaller leak jet if you still have a low end bog.

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