A month ago I bought a 1985 Honda XL 250R. 12000 miles. The previous owner said he had a new piston and rings installed.
The bike runs fine. A few bad threads and some small oil leaks but nothing major. Good power across the RPM range but, is has a serious taping which I assume is a valve. Working with a gage I checked the clearance using the following numbers .05MM (.002) intake and .08MM (.003) exhaust.
The exhaust valves seemed very close so I made no adjustment. I did adjust the intake as they seemed a bit loose. After restart, I still have the same tapping. For a test I removed all play from both intake and exhaust. Now set at zero. Restart and the tapping is still there so the problem is not the valve lash. I then set the valves back to the specs of .002I and .003E.
I wondered if it could be detonation from 85 octane fuel but it's more of a tap then any ping I have ever heard. While the engine is running if I press the compression release lever in with my finger to engage it, I get another similar tap which is in harmony with the original tapping I am trying to get rid of. So it makes me think it is related to a valve.
Now I am wondering if I have a bent valve or what?
Any experts have any ideas?