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06 crf 450 afterfire/backfire HELP!!


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Hi am am new to this forum

i just bought a used 2006 crf 450 it doesn't have very many hours on it the hour meter says 40 hrs but i came from Arizona USA. i live in Canada BC my altitude is about 720. the problem is when i let go of the throttle the bike it pops and bangs (after-fire)like crazy. When i hold the throttle revving it does the same thing after-fire popping and banging??

I just checked my valve clearance my intake is 0.16mm or 0.06in (to honda specs) but the exhaust valves are at 0.20mm one is tight the other fits nice (out of spec i am in the process of getting the new shims) i have a 168 main jet and the needle clip on 5 slot i have tried changing the clip position and adjusting the pilot jet several times no luck.

Would the exhaust being out of spec clearance be the reason for the after-fire ???

Any help and advice would be nice ๐Ÿ‘

Thanks Aaron

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okay so i went out tonight to take the cam assembly off so i could get at the exhaust shims, when i went to get it in top dead center i lined every thing up but i noticed the cam was 180 degrees the wrong way at top dead center, the lobes were facing the front of the bike ??? i didn't think a bike could run that way, i am thinking this could be the problem for the after firing???

thanks aaron

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If you try Eddies "how to confirm your pilot circuit setting" first then start trouble shooting from there you wont be spinning your wheels.

In other words, don't spend the time tearing down the bike and carb until you have a good idea whats going on. It just to much trouble to tear down. Know what I mean?

Try this first and tell us what you found. (same link as above in my last post)

how to confirm your pilot circuit setting

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If you try Eddies "how to confirm your pilot circuit setting" first then start trouble shooting from there you wont be spinning your wheels.

In other words, don't spend the time tearing down the bike and carb until you have a good idea whats going on. It just to much trouble to tear down. Know what I mean?

Try this first and tell us what you found. (same link as above in my last post)

how to confirm your pilot circuit setting

on my crf450x I can get the pilot out just by tilting the carb... can you do the same on a 450R? or years other than 07?

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on my crf450x I can get the pilot out just by tilting the carb... can you do the same on a 450R? or years other than 07?

I not 100% percent sure on the 450's. I have to "rebuild" the bike on my 07 CRF250R to re-jet it. It sucks and takes for ever. It's a real b****.

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I not 100% percent sure on the 450's. I have to "rebuild" the bike on my 07 CRF250R to re-jet it. It sucks and takes for ever. It's a real b****.

dang that stinks... My 06 250X it is one of those just barely things as far as being able to get the pilot out.

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okay here is a update i talked to a guy on the chat here the other night and he said it sounded a lot like my pilot screw and slow jet. so i went and tested it at 1/2 turn out and aounded horrible then i went and twisted it 3 turns out and almost got rid of it so i know i need a bigger slow jet ๐Ÿ‘, also i just finished cleaning the carb twice

thanks everyone

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