Posts tagged Valves
The top end of the Honda XR650R is very robust and long living. However, if you push it too hard you can eventually hit a wall. The pictures below are from a motor that was running a stage 2 cam. This cam puts the valves VERY close to the piston when fully open. When the cam chain stretches a bit then Kablammo!
Checking and adjusting the valves on the XR650R is a simple procedure. Here is how.
- Remove the seat and the tank from the bike to give you access to the top of the engine.
- Clean around the valve inspection covers so there is no loose dirt.
- Remove the valve inspection covers.
- Remove the large left side engine cover to expose the flywheel and timing inspection marks.
- Rotate the crank counterclockwise using the large bolt on the flywheel. Line up the “T” mark with the small notch at the top of the housing.
- Wiggle the valves with your fingers. If they wiggle a little up and down then you are ready to check and adjust them. If there is no play in them rotate the crank again, match up the “T” and check again. The goal is to adjust the valves at Top Dead Center on the compression stroke. At this point all four valves will have wiggle in them.
- One by one insert feeler gauges between the valves and the tappets to check clearance. Intake valve clearances should be 0.15mm +/- 0.02mm (0.006in +/- 0.001in) and exhaust valve clearances should be 0.20mm +/- 0.02mm (0.008in +/- 0.001in)
- The feeler gauges should have a slight drag when slid between the valves and the tappets.
- To adjust the valve put a closed end wrench on the tappet nut and crack it loose. Use a screwdriver to adjust the tappet up or down to increase or decrease the clearance. Once it is in the right position, tighten down the tappet nut to hold it in place.
- It is often a bit fiddly to get the tappet set perfectly. It will sometimes spit itself a little bit when tightening down the nut. You’ll get the hang of it quickly.
- I prefer to spin the engine over a few times then recheck and verify all the clearances.
- That’s it! Put the valve inspection covers back on. Put the side cover back on. Put the seat and tank back on.
- Go riding!
(This post could use some photos. Anyone have some to contribute?)