I just came across this really good video created by the guys at Hot Cams about how to adjust and check the valves on your 4-stroke thumper. There are 2 videos, one is specific to the Honda CRF450R, and it’s single cam or “Uni-cam” the other is specific to the Yamaha YZ250F and its dual cam setup. The Honda’s (CRF250R & CRF450R) are the only ones with single cams. All other bikes are dual cam bikes.
The video is really good, and actually quite thorough. I’ve checked, adjusted, and even replaced my valves on my old 2003 CRF450R, so I’m fully aware of everything that’s involved with doing this task. I’ve actually installed a stage 1 Hot Cam too, so this is not something new to me. I’ve also checked and adjusted 2 different YZ250F’s (2003 and 2004), and the video for them is very well done as well.
Here’s the link to the single cam video: Honda CRF450 – Valve Clearance Inspection and Adjustment
Here’s the link to the dual cam video: Yamaha YZ250F – Valve Clearance Inspection and Adjustment
Let me also say that having the Hot Cams complete shim kit is a must. I own the shim kit for the 450’s (9.48mm) and my brother has the kit for the 250F’s (7.48mm) and both are worth there weight in gold when it comes time to adjust the valves clearance. You can pick them up here –> Hot Cam Complete Shim Kit
Before I had my shim kit, I spent $5.00 a piece for 1 shim. I’ve heard that some dealers charge as much as $8.00 a piece for them, and that was if they even had the one you needed. The kit completely eliminates the chance that you won’t be riding this weekend, as you always have the shim you need.