Crf 250 wont idle. Tried everything, please help!

Hey guys

I've been having a heap of trouble with my 04 crf250r

It kick starts fine but will not idle, it idles for a bit but it sounds really irregular and then gradually dies. When revved it backfires badly.

 

I just got a new 07 head for it because I've been having trouble with the valves. I installed the kibblewhite ss valves and springs into this head. I hoped this would fix the problem. I have triple checked the valve clearance and its all within spec as well as the timing.

 

I have played around with the jetting and achieved nothing. I have put in from a 162-182 main as well as 40 up to 52 pilots. It has a 50 leak jet. My old jetting was set at 172 main and 45 pilot and it ran fine so it doesn't make sense to be jetting as this just happened out of no where.

I have played with the pilot screw and idle screw and nothing worked.

 

I have checked the air box and intake for leaks and all of the clamps are tight.

 

I have changed spark plug and fuel and tried running without the air filter

 

I have fully cleaned the carb and jets

 

It has a new stator, new piston, crank, cylinder, cam, pretty much replaced everything

 

I am out of ideas so can someone please help me? thanks

Idle is pilot jet, slow air jet, fuel screw. Choke and hot start also can come into play as well as the slide vacuum release plate seal.

I found out what was wrong with it...

It was taking too long replacing and checking everything one by one so i replaced the coil, cdi and cleaned the electrical connections all at once and one of them fixed it.

Thanks for the help

Was going to say electrical....glad ya found it. Having atvs for 25 years have not had electrical issues until last four years.....no cant escape them...lol

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