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2008 Crf450r Constant Speed Missing/Hesitation

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Hello All,

Last weekend at the track I noticed that when I was cruising around the pits there is a very annoying miss/hesitation around mid-throttle or any constant speed. Also, it seems to get worse the warmer the bike gets. The issue also seems to go away when I am accelerating rather hard.

When I pull the hot start in with the bike running it revs high. 

I know this is a race bike and it is made to be ridden hard all the time, but this is getting to the point where it is almost embarrassing for myself to listen to when cruising around the pits and track. 

The carb was recently cleaned 6 months ago. Any help would be greatly appreciated! 

Edited by wioffroader

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WAY too rich. And the spark gap is too big, too. drop the pilot down to a 42. Start the adjustment of the fuel screw at 2 turns out and get it warm, and get the fuel screw set correctly. And, so you know, you cant set the fuel screw correctly until the thing is HOT, not a little warm, HOT. Like hot enough to burn the shit out of you while you're trying to adjust the fuel screw. I know, trust me. But, once you get it dialed, it'll start first kick all the time and run nice. But that plug is way way too rich. Close the gap up to about .030- .032" the OEM ignition isn't all that great, jumping .040 is iffy.

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WAY too rich. And the spark gap is too big, too. drop the pilot down to a 42. Start the adjustment of the fuel screw at 2 turns out and get it warm, and get the fuel screw set correctly. And, so you know, you cant set the fuel screw correctly until the thing is HOT, not a little warm, HOT. Like hot enough to burn the shit out of you while you're trying to adjust the fuel screw. I know, trust me. But, once you get it dialed, it'll start first kick all the time and run nice. But that plug is way way too rich. Close the gap up to about .030- .032" the OEM ignition isn't all that great, jumping .040 is iffy.


Ok thanks that is what I figured. I'll start doing that tomorrow. Could it be a worn carb needle? Would a hotter plug help too?
Thanks for the help.

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Check the float levels too. When checking the float level, you can just flop the carb upside down. You need to roll it over slowly until the needle seats. If you just flop it over, there's a tiny spring in the float side of the float needle that gets overcome by the weight of the float. If you set the float height there, it'll end up WAY low.

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UPDATE: Replaced the jet needle and it improved slightly but was still hesitating mid throttle.
I think found out that the jet needle holder was also worn. I replaced that and now it runs perfect. The worn holder was letting extra fuel past causing the rich conditions mid throttle.
If anyone has any questions let me know!

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