I recently bought a used 2004 CRF 450R and this is the first time I have ever had to deal with valves, it has always been 2-strokes.
After roughly 5 hours of riding, it will not start. After reading almost every thread about valves on this site, I decided to check and adjust them myself.
My question is if the intake valves have zero clearance, should I buy valves that are .006" smaller which would put them within the specified tolerance of .005" - .007" or should I buy a few sizes?
Also is it possible to shim the valves enough to get a few more hours of riding, or should I save the headache and send it out for valve work? I will be riding Michigan trails only, no racing.