Exhaust popping 08 yz450f

Bought a 08 yz450f bike is immaculate in every way an older gentleman owned it and everything is all original from factory but suspension upgrades. Only question I have is it pops when reved and on deceleration but starts going away the warmer it gets just wondering if that is ok

Sounds lean pop on decel is normal if not excessive if power loss also then might be more serious like bent valve I'd check pilot jet maybe bump it up I always ran a jd jet kit in my 08 and it was real snappy

It's okay fine for a 08 YZ450 putting a bigger pilot in it may lesson it a little.

Before doing anything to the carb, be sure you don't have a leak in the exhaust system causing this.  It would be at either end of the header.

 

If the pipe's OK, then try setting the pilot screw according to the manual.  If that fails to reduce it to a normal level, then go up a jet size on the pilot, but not until you're sure it needs it.  

 

It's normal for the bike to pop a little some of the time.  It means it's jetted right.

 

http://www.thumpertalk.com/topic/340570-popping-on-stock-06-yz450f-exhaust/#entry2983539

 

http://www.thumpertalk.com/topic/271735-how-to-confirm-your-pilot-circuit-setting/

This thing pops a lot on decel and if you rev it

Guy said the carb was rebuilt with oem stuff and has only had two rides on it. Air screw was 1 3/4 turns out when I got it I bumped it to 2 1/2 and it still does it

Carb is dirty and I fell to the devil carb cleaner I couldn't remember what rubber would ruin but the slide seal is gone bike has stock jetting 160 main and a 45 pilot 3rd clip position. Question would I have to do any jetting difference with a factory 4.1 slip on no header just the muffler thank you for your help

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