Valve issue on a TE310 (2011)?

Dear all,

After detecting some loss of compression during kickstarting, I inspected the valve's clearance and found that the gap of the right intake valve was completely inexistent, no clearance at all. I re-shimmed with a 1.40mm shim (original was 1.65mm) and the clearance become spot on.

500km later the loss of compression during kick starting come back. I checked the valves again and found that there wasn't any clearance in the same valve (all other were in spec).

Is it normal for a valve to stretch at least 0.40mm (0.25mm + 0.15mm) in such short time??? Can it be a symptom of a bent valve, deformed valve face, defective valve seat, or something else? How worried should I be atm??

The bike has ~7500km.


Many thanks in advance.

PS - It may be nothing but both times I also found small black debris in the hollow part of the cam, but can’t tell where it might come from ... maybe some seal debris?

Your situation is common. The issue is dirt has entered the engine and worn the hard facing off the inlet valve. You need to replace it. It’s common for the RHS intake to wear first due to the angle of the intake from the throttle body.

Good Valve:


Worn Valve:

Thank you for the insight. In your opinion, should I replace the LHS valve as preventive maintenance as well? Though, it never had to be adjusted since new, neither the exhaust ones...

Check the valve surface where it contacts the cylinder head seat with a LUPE 20x magnifying eyepiece. My LHS inlet was fine however I replaced both anyway.
You can probably leave the LHS valve if the clearance hasn't changed.
I didn't need to touch the exhaust valves, they had not moved.

Thanks once again. I'll investigate everything carefully asap and update this thread accordingly.