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runs great hard hot starting

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I have an 04 crf450r. It has a Big Gun full system evo x series exhaust. It was running good but popping at top end and at deceleration but started well. By-the-way it had the exhaust on it when purchased. I took it to a mechanic friend of mine and checked the jetting. The slow jet was a 42 and the main was 165 I think.

We changed the jetting to 48 and 170 and it runs perfect. Acceleration,response and top end are seamless and smooth. The bike has power that it did not have before. The problem is having been woods riding for a while if you stall the bike it takes about 5 min to start. Using the Hot Start does not help either.

The valves are in spec and hot start and decompression are as well. Any thoughts on a solution to the hard starting issue.

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Jetting is not right. To rich on the pilot. Popping can mean lean condition or exhaust is sucking air. With these exhausts they will pop even when jetted right so don't use it as an indicator. The pilot will not affect much of anything but off idle. You could go to a 42 and raise the needle one clip.

Check the cranking compression when hot. Should be about 80PSI. If not, adjust the decompression adjuster until you get it (provided the valves are in spec). If your valves are getting tight the compression at cranking will be reduced if it was set when the valves were in spec.

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I had a similar problem with my 05 when I first picked it up. Not knowing the history of the bike I did what anyone should do and immediately dove into checking valve clearance, oil change ect. Found out that this particluar bike was hard to start when hot because the cam was one tooth advanced and the timing chain had stretched enough that even with everything lined up it would be just under a half tooth off at best. Bought a new chain while I was waiting on my kibblewhites to get installed and everything except my collarbone is right in the world.

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go to a 2 stroke and that wont happen

I can't believe you even took the time to type this idiotic post.

But thanks for showing us all your IQ.

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I replaced the timing chain and tentioner. Had a complete valve job done and have even checked the clearances. All is well. It is probably the low speed jet that is to big. It's a 48 instead of the stock 42. I was thinking of going to a 45 to see if that cures the problem. If not go back to stock 42.

I just came from a cr 250 to the crf450r and love the 4 stroke. I like them both but think I'll stick with the 4 stroke.

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