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Old 05-09-2009, 11:32 PM   #1
DvlRacer
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CRF450 Advice Needed

I have an 05 crf450r that isn't currently running. Took it to the shop and they said compression is 30 when it should be 78. They say it needs a top end rebuild, but in my experience isn't it more or equally likely it needs valve work? Also, I'm new to the big 4's, I've done top ends on 2 strokes many times, is there anything special I should look out for before diving into this motor? Where do you order your rebuild kits? If it does need valve work who would you recommend? Thanks for any and all advice.
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Old 05-10-2009, 01:04 AM   #2
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where do you live? ill take a look at it..dont try rebuilding it your self! seen to many people screw those up cause there use to the 2 strokes.
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Old 05-10-2009, 07:33 AM   #3
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Huntsville but could get the parts and meet you.
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Old 05-10-2009, 10:30 AM   #4
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Old 05-10-2009, 11:02 AM   #5
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I was under the thought that you don't have much success checking the compression on the CRF450 because it has the auto decompression built into the camshaft. So when you kick it over, the compression will be less to help with starting the bike.

When the bike quit running, what were the symptoms? It would probably be a safe bet to check the valve clearances. My bet would be the intake vavles are zeroed out. The exhaust valves are generally fine. Checking the vavles takes about 30 min to do, simply pull the tank, pull the vavle cover and check vavles (make sure the piston is at TDC!). That will answer a lot of questions there, but like I said, if it has stock vavles in it, chances are the clearance is gone.

My head is currently at Motorcycles Unlimited getting Kibblewhite SS valves and springs installed. SS vavles and springs are the way to go for longevity in these bikes. You can rebuild the head with stock Ti valves, but you will be in the same situation in about 40-60 hours.

As for doing it yourself, you could if you have the proper tools. If not, it would be cheaper to have a shop do it for you. Make sure that you have the vavle seats recut when you install new valves!

Check out Thumpertalk, there is a lot of info on the CRF450's.
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Old 05-10-2009, 11:12 AM   #6
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Squanto up at Motorcycles Unlimited has a 450R and he seems very knowledgeable about these engines. If you pull the engine yourself, a full rebuild should'nt cost you too much. I've got a Haynes manual if you wanna borrow it.
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