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O5 YZ450 Popping

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I just got an 05 yz450f. From the dealer it was crisp and ran pretty clean, but off the throttle it would pop and crack a lot. I put in a 48 pilot wich was 45 stock and that did not help. So i put in a 168 main and that did not help either. Stock was a 165. Then i put the needle at the number4 clip position instead of the stock number3 position. this did not help but it blew black smoke.Now i put the clip back at number3 and bumped the main up to a 170 and the pilot to 50 wich is too big because the engine will not die when i screw it in all the way. Any suggestions? I am a bit lost at the moment. Oh yeah after my first ride i put on a muzzy exhaust, but it has the same pop as the stock pipe did, no difference. What are your thoughts and i appreciate all comments. Thanks a bunch.

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Go back to stock jetting settings and adjust your air/fuel screw - this is probably your issue. Stock jetting is ok/good for most places -I do not see where you live or altitude. Clip to 4th position is crisper throttling. The JD kit is awesome for your 450 - it will make it very crisp. For more info on fuel/air screw do a search - I start with 2 full turns out from full in. Get yourself a adj air fuel screw as you will adjust for temp changes etc...hope this helps :cry:

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Make sure you don't have an exhaust leak at the head as well. Also, look for a cracked boot between the air box and carb, make sure the carb clamps are tight, and check for any other air leaks in the intake tract.

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Where could I get an adjustable air fuel screw? That would be nice because it is pretty hard to get at.

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Uh, I've got a Zip Ty fuel screw on my 03. Works pretty good. Unless they make 'em for 250's and not for 450's.

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