Ask Dr. Dirt: Replacing Valves

Dirt Rider’s Chief Physician AKA Dr. Dirt is Scot Gustafson. If you have a question about bike maintenance, set-up, tuning, or if you need help diagnosing a problem or just want to know how something works, send your question, along with your first and last name and your city and state, to We may edit your letter and might also use it in Dirt Rider Magazine’s letters section.

Dr. Dirt,

Hey I need to put new valves in my CRF250R and I need to redo the valve seats. I'm curious, what’s involved in redoing seats? And should I also replace the valve seals while I'm in the motor?

Nick Aben

Yes, you should always resurface the valve seats when replacing your valves. Valve seats are resurfaced using specific hand cutters or elaborate machines so the seat will have a perfect seal with the valve. It is a job for an experienced mechanic or engine shop. Replace your valve seals and valve springs while you are in the engine.