maxy b

Member
Oct 10, 2007
15
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08 Crf 250R!!! It will definately be a step up from my 04 Cr125!
Anything I should know about the bike... tuning tips? Maintenance tips? Anything?!?!?
 

Rich Rohrich

Moderator / BioHazard
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Jul 27, 1999
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Here's the original links from DRN that Eric's valve train articles came from :

http://www.dirtrider.net/forums3/showthread.php?t=115200

http://www.dirtrider.net/forums3/showthread.php?t=115201

The specifics from the articles on the CRF250 are quoted below:

CRF250
Although no specific service limit is advised in the Honda service manual, you should replace all the valves and springs at the same time as the piston. Honda recommends changing the piston every 15 hours, and in practice I estimate the valve train and piston to have a useable service life of about 30 hours. In fact the valve train usually wears out before the piston. The dangers of leaving the valves in place until the engine won’t start anymore, is that the valve seats will become damaged and require an expensive service of valve seat reconditioning. In a case like that, considering that new head is so inexpensive, it may be cheaper to buy a new head rather than fix the old one.
Another problem that is rare for the CRF250 is a failure of the left side cam bearing. If the engine becomes particularly noisy at idle, or if there is a thick black residue of rubber present under the valve cover, then the cam bearing is worn and placing a greater side load on the cam chain guide. The rear tensioner chain guide is coated with rubber, which accounts for the thick black residue.
 
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