Does this sound like clogged jet? Ideling problem

Does this sound like clogged jets?


I have a 2008 CRF450X. New cylinder, piston, valves and reconditioned head. Starts on the first kick, lots of power and good compression. After reading past posts it sounds like a bike that won’t idle is most probably due to clogged jets. I’ll start my bike, adjust the idle so its ok, maybe a slightest bit on the high side. But as I ride I keep having to adjust it, it might be perfect then all of a sudden it is ideling  super high, I back out the idle adjustment and its ok for a bit but then revs high and this keeps repeating itself. Clogged jets? The cable routing is ok, no sign of vacuum leaks.


If so any suggestions on what to clean them with? I’m in Senegal and can’t find any carburetor cleaner.


Thanks, Steve

DO NOT USE carb cleaner!

Rubber parts will melt. Use only spray brake cleaner and compressed air.


You have the classic hanging idle issue.


You need to replace your stock fuel screw with an R&D remote fuel screw, and learn how to adjust it correctly (in the pinned posts it tells how).

If it idles at all the pilot jet is fine.


If you have not un-corked and re-jetting the carb, you will continue to have issues with running as the motor gets hot. 



The guy I bought the bike from in Doha uncorked and rejetted the bike. It ran great for 30 - 40 hours and then the idle problem began while I was there, it gradually got worse and worse. I did the engine rebuild before moving to Dakar.


Thanks for the heads up on the carb cleaner. It will definitely idle, but I justcan't keep it at the correct idel speed, it races or it dies. I'll check the post you mentioned. Any other thoughts would be greatly appreciated. I've had XRs forever in Egypt, Libya and the UAE...they were simple and I could figure them out. I'm thinking the CRF might not have been the best choice for me here, maybe above my mechanical ability.


Thanks and any other thoughts would be really appreciated.



Also check for an exhaust leak, usually between the head and header pipe. Loose or leaking exhaust gasket. This will cause a lean condition too.

Here's some advice, from JD Jetting:



Setting the fuel screw mixture-
Try adjusting with the motor fully hot, and turning the fuel screw inwards until the idle slows or runs rough, then turn outwards 1 1/4 turns from this position. For example, if the idle slows or runs rough at 1/2 turn, then set the fuel screw to 1 3/4 turns out (1/2 + 1 1/4 = 1 3/4).
See-    to understand how the fuel screw can affect the idle speed and air/fuel mixture at idle. The target range for the air/fuel mixture is near 12.5 to 13:1 at idle.

Thanks you guys, I appreciate the advice and suggestions. I'll give it a shot tonight.


Take care, Steve

Sounds to me more like an air leak somewhere.


Besides the exhaust, check:


1. Slide seal is in good condition and installed correctly (not up side down, which is easy to do).


2. Band clamps on the carb are tight.


3. Your hot start plunger is in tight, fully seated, and is working correctly lock to lock (swinging the bars all the way each way does not pull it).



Almost sounds like ethanol poisioning to me but in Libya ?  Probably don't have ethanol additives. 

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