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Discussion Starter · #1 ·
I have a major issue with my 06 CRF450R with it not wanting to start up. Its got compression but it takes like 15 kicks for it to start up. Then when I do get it started and ride around for it to warm up a bit it shuts off when I pull the clutch in to keep the motor running. A buddy of mine and I took the head off and checked the valves with a feeler gauge. Im not too familiar with motors on dirtbikes but looking at the dirtbike from the back to the front. My left valve is at .005 and my right is at .001. We guessed that because we couldnt even fit a feeler in there to know what it is. I need help on what I should do. Take it to Honda and pay a but load of money to get it fixed or try it on my own with my buddy by a manual.
 

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The Toad
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Unless you learn to do your own maintenance on a dirt bike it will literally eat you out of house and home. Valves need regular checking. Too tight a valve can contact the piston crown and when that happens you are looking at serious costs.

Just follow the instructions in the manual exactly and you should be fine.
 

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Aging Cafe` Racer
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Be sure to soak the cylinder head in warm salt water for a day or two before you reinstall it.
 

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MODERATOR X
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Lezeee, an '03 CFR450 Honda....hmmm....most likely has about 30 hours riding time on it, right? If I read all the tech publications on the mighty 4 striker right it's about time for a MAJOR TOP END JOB, meaning new valve seats, camshaft bearings, piston/rings, wrist pin, etc. People wanted a works type four stroke, and they got it, along with the maintenance that goes with it. Do youself a favor and dump that maintenance nightmare and buy a 10 year old CR500. You'll wear out before the CR500 does...
 

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Those clearances sound way too tight. Are you sure you're measuring from top dead center? I don't have a diagram or shop manual for a CRF motor handy (couldn't find a MO article either), so I don't know if you've got four valves (probably), and are just measuring two of them, or if you've got a two valve motor. Either way you need to get a hold of a shop manual, find out the right values for the clearance, and adjust them. Adjusting valves isn't brain surgery, but it does require paying careful attention to what you're doing. If you have to remove the cam to install new valve shims, make sure you replace in exactly the same position. There is probably other maintenance you should be doing if your valves are (what sounds like) that far out of spec.
Mind you, Cuddy is probably right, but if you want to get it running properly in order to dispose of it, get a manual. Don't know where you are located, but you can probably find a local in a CRF owner's group who's done this before and is willing to help out.
 

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Discussion Starter · #7 ·
Thanks for that reply man i appreciate it. I have two valves I checks my manual that I have at home. I knew my motor was at top dead center because all the marks were lined up correctly that the book speculates on. Im taking my bike to a Honda shop by me and they're going to check it out. Im hoping that its just reshimming the valves and Ill be on my way. I wouldnt think Id have this problem because I change my oil every three rides religiously along with my oil filter and I clean my air filter and air box every two rides. So this really has me dumbfounded.
 

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The Toad
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Thanks for that reply man i appreciate it. I have two valves I checks my manual that I have at home. I knew my motor was at top dead center because all the marks were lined up correctly that the book speculates on. Im taking my bike to a Honda shop by me and they're going to check it out. Im hoping that its just reshimming the valves and Ill be on my way. I wouldnt think Id have this problem because I change my oil every three rides religiously along with my oil filter and I clean my air filter and air box every two rides. So this really has me dumbfounded.
The problem is that those 4stroke MXers have the same extremely light components that you would only find on works bikes in the past. They simply wear out very quickly. The only solution is to either get a 2stroker or one of the less extreme 4strokers and live with the reduced hp.
 

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Hopefully, there's enough adjustment in the shims to re-establish proper clearance. If not, you're looking at new valves and possibly installation of new seats.

With the head off, I'd be tempted to install new Kibblewhite valves (They're SS, not titanium like the OEM). They will last longer, and take abuse better than the stock valves.

KPMI - KPMI

If you download their catalog, there's a neat story about the founder, and cool pictures scattered throught out the rest.

This is a common modification to these high strung 4 strokes.
 

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Discussion Starter · #11 ·
I took my bike to Honda and they shimmed the valves to proper clearance. However soon I will have to replace my intake valves or I will lose power. Im going to look for those Stainless Steel valves you mentioned. Thanks buddy
 
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