I have CRF450R that I race cross country and Enduros on. I weigh 225 with gear on and am a B rider. I am 47 years old in good physical shape.The engine on the 08 CRF450R started acting funny about 5 hours ago. Didn't start as easy as in the past. Now wont start at all. Checked valve clearances and intakes are Left, could not get a .03mm feeler gauge in. The Right .063mm gap. Exhaust left is .203 gap and right gap is .203.So, looks like I am going to need to do a valve job. While I am in the engine, I want to replace the piston and rings.My questions are:1. Whose valve components would you use and who to do the work?2. What piston would you use and would you stay with stock compression or go higher. (My piston is stock now)3. Would you change cams?4. Would you replace timing chain and gears?I am open for all suggestions.Thanks in advance for the help!