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Discussion Starter · #1 ·
I was riding around last week and suddenly something started tapping bad.

Well i thought it needed a new cam chain. Got the crf450 cam chain and tore into the quad. Got the head cover off and noticed both bolts holding the cam to the cam gear were sheared off, but still in place. It skipped 2 teeth. The gear had alot of play in it. There was some metal shavings in the oil, i removed the screen on the bottom of the crankcase and it was pretty clean. But there was shavings from the top end to the crankcase. It ran great before this happened, and only ran not even a minute afterwards with no load on it. So it shouldnt hurt the bearings right?

I was told that flushing the engine out with oil a couple times and this should be alright? The bolt ends are still in the cam, and the holes in the cam gear might be a little bored out, still usuable? Might be able to get some pictures.

Thanks
 

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Don't draw any conclusions without further investigation.

First, I am confused - are you saying the engine ran after the cam bolts sheared?
Second - did the cam chain jump two teeth or is the cam sprocket just two teeth out of position? If the chain jumped two teeth, it's very likely you have some bent valves.
Third - what caused the bolts to shear? Did they get loose and catch on something, or did the cam seize causing the bolts to shear?

I'm going to guess the bolts came loose and over a period of time wore in two.

Throw the sprocket away. Inspect the cam carefully (might be best to throw it away also). I would really suggest you take it to a qualified mechanic. You might have more serious problems lurking in that mill. This sort of problem doesn't just happen; it sneaks up over time.

A mechanic will ask for more details, like has it been worked on before, who did the work, what was done and why was it done? Depending on what the cause of the problem was, get ready to spend $450 to $850 to get it fixed right.
 

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Discussion Starter · #3 ·
The sprocket was 2 teeth out. Can i get it rethreaded? Really don't want to put the stock cam back in.

It still had the same amount of power before i shut it off. Bent valve would indicate loss of power right?

I have a pic but don't know how to put it up.
 

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I don't know if a pic would help, but you've told me something I didn't know - the cam is not stock.

If the valves were bent it would not start at all.

No - the cam cannot be rethreaded - the cam is at least as hard or harder than a threead tap. If the threads are not really messed up, they can be cleaned up by running a tap through them.

OK?
 

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Discussion Starter · #5 ·
Ok thanks. For now i'm just going to put the stock cam back in. Ordered new cam gear bolts, the cam gear is fine along with the tensioner, and have the chain coming tomorrow.

I stopped by the local honda dealership and talked to a mechanic, and he pretty much told me what you just said...the cam is junk. Not only that, but the cam had stress fractures on the lobes. He said it was ready to break apart at any time, and i was lucky only this happened.

I also was wondering about how to flush the motor. My dad said to flush it with kerosene. I can see kerosene flushing out grime, but metal? Maybe just flush it 3-4 times with cheap oil and keep flushing out the same filter with kero? or is there a better way?

Thank you
 

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Flushing with kerosene (or diesel fuel) is how I do it. Any metal too heavy to flush out will just lay on the bottom of the motor and not hurt anything. Flush it a couple of times, put a new filter and oil in it and cross your fingers. Sounds like the level it is being run at could invite failure of something at any time anyway. Good luck
 

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Discussion Starter · #7 ·
Thank you.
 
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