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2003 YZ450F running issues

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So I got a 2003 yz450f 

It starts and runs but has a high or in consistent idle. Cleaned the carb very well and put back together properly (to my knowledge) had a buddy here too that's somewhat familiar with bikes too. 

 

Can't figure it out. Jets are stock jets and I don't know much at all about jets or carbs for that matter but trying to learn. 

Also not sure if it matters but the choke plunger won't stay out also. Was probably going to replace unless its not a big deal. 

 

Where should I start with this thing ?! Thanks 

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Fix the choke plunger, and replace the stock hot start with another choke plunger assembly (the stock hot start assembly is typically a source of air leaks)

Install an R&D remote fuel screw, and follow the correct adjustment procedure (starting with a low idle and turn out to 1.5-ish turns)

If your bike ever ran well with the jetting you have now, then it's not the jetting.

Edited by THE KRAN

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High surging idle is usually a sign of a lean condition.  Either caused by a clogged key or fuel passage, lean jetting, or an outside source allowing extra air into the system.  Take a propane bottle (brake cleaner and staying fluid work too) and "spray" the unlit gas around the intake and intake boot.  If the idle changes at all, you have an air leak.

 

I was suffering from this too, recently.  Went thru all the motions and couldn't find a leak anywhere, until my exhaust started making noise.  Turned out my head pipe had been cracking which ended up being the source of my lean condition.  Replaced the pipe, and no more popping or surging idle.

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