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Blown motor. Need suggestions.

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CRF450R - Racing a harescrambles, everythings going fine, then my motor starts to pop. After about 4 pops, it just up and died. Now won't start. It was a very wet race, with creek crossing and such. I didn't get into anything too deep, say over 10". Also had alot of 5th gear, wide open areas. Any ideas what could be the problem?

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CRF450R - Racing a harescrambles, everythings going fine, then my motor starts to pop. After about 4 pops, it just up and died. Now won't start. It was a very wet race, with creek crossing and such. I didn't get into anything too deep, say over 10". Also had alot of 5th gear, wide open areas. Any ideas what could be the problem?

Ouccchhhh.

Could be a plethora of problems :)

We might be able to narrow it down a little better with more description, but until you take her apart, there is no way of knowing exactly whats wrong

Good Luck Man

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could just be water in the carb, i would start there...

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If the compression feels "normal", then proceed to check for spark and fuel. But if you feel no or low compression, then you going in deep.

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Last night, the bike fired right up on the first kick. Compression feels normal. bike idled fine, revved fine. I didn't take it out and ride it. hmmm. Could it be related to high temp? I had been riding hard for about 2 hrs. when this happened.

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I will sell you my 2005 CRF450R motor...I am turning the chassis into a 500AF

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If its fine now, it must have been water getting into the electronics. Dried out now, I guess. If you're going to be doing any more of that kind of riding, I'd go through the wiring and seal it up as well as you can.

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I went ahead and did a top-end rebuild since it had been quite awhile since this had been done. Everything internal looked fine to me. Carb was indeed pretty dirty, so that may have been my previous problem. Now on to the top end....I have gotten it back together and ridden it a couple times. It is extremely hard to start. the kickstarter will stick a lot of times at the top of the stroke and not even come down. this doesn't feel real good on my recently recovered broken leg. I had a problem with the piston kit, though. the intructions that came with the piston were wrong in that they told me to install the piston backwards, intake side facing the exhaust side. I got the bike back together and started it, and it made a clunking sound. I thought it was the cam chain at first. I only let it run for about 10 seconds. So after disassembling it, I figured out that the piston was in backwards. Could this have bent the valves or caused any other problems. I could depress the valves by hand, and they don't stick or anything. I didn't see any physical damage to anything else. I've got the alignment marks lined up perfectly on the crank and the cam sprocket. The exhaust valve clearances are both at .009", and they are supposed to be at .011". my local Honda dealer told me to leave them at .009", and that after breaking in the bike awhile, they will loosen up. Could this tight valve clearance be causing the hard starting or the kick starter to bind up? The bike seems to run fine. It feels a little rich to me. Somewhat of a blubber at all speeds, so i may need to rejet. Any suggestions would be greatly appreciated.

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check the decompressor rocker arm clearance. If it is too loose it can make the compression keep you from kicking it

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