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Discussion Starter #1
06 510smr. i am borrowing it from a friend and am tuning a bit for him while he is out of town. it is ruunin rich. how do you lean it out. i know it's a keihin fcr41. i was backfiring kinda bad on decel if you were getting on it. which leads me to believe it's rich. i checked the main and it was a 185. little big i think. i pulled it and put in a 182. took her for a spin and it runs great. little pop here and there but damm close. i am concered about sitting at idel if you try to wack the throttle it chokes out. ideas. other than that this thing is a monster.
 

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What is the needle code? Most likely you need a thinner diameter needle? The last letter of the needle code is associated with the diameter. If you have a JD kit, they might send you another needle to try out.
 

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If you're the original owner then see the manual. If not, there are two screws at the top of the carb and one allen bolt that will get you to the needle. The JD kit is really the way to go. You get good support from JD, and they've done the work ahead of time.
 

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Discussion Starter #7
ok let me try to explain again. when i would really get on it and let off the throttle it would pop. i has alway done this since he has had the bike. it always seemed like it was running rick. so i took out the main jet (i guess) by pulling the bowl drain. it was a 185 so i dropped it to a 182. rode ti really getting on it and letting off the throttle. very little popping. the other question is that it idels finie but when you really whack the throttle from idle it dies. you really have to whack it though. i just want to fine tune it since he is not the greatest at these things
 

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The pilot jet controls the popping and then there is very small overlap with the diameter of the needle. Unless you warmed up the bike for a good 25 minutes your conclusions aren't worth much. My bike will pop a lot when it is cold out and I first start riding, but when warm it is manageable.

The diameter of the needle controls that first 1/8 throttle. It sounds like you're too lean and it is dying on you when you "whack" it off idle. Again making sure the bike is warm is the key before you make changes.
 

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Bottom of the bowl, and very hard to reach as it is recessed. You might need to fab a screwdriver to fit in there.
 
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