What are the symptoms of a sticking valve?

[MB-Ian]

Intake valve, specifically? Anyone know of any good videos showing how to detect a sticking valve?

I still have the odd cough coming through the RH carburetor at idle when the engine is fully warm.

When riding at any reasonable speed (so 2000rpm and above) there's no cough or misfire, and I've checked the vacuum on both carbs, they are equal - 12in max at idle speed of 1200rpm (vac gauge pointer wavers between 8-12in).

If a valve is sticking at idle speed, will it worsen as the engine speed increases? If so then I probably don't have a sticking valve....

I.

 

[Tech7]

Hi Ian. The cough is coming through the carb? If so, it does sound like a valve. It won't necassarily get worse with engine speed. I assume you have checked valve clearances. Your not losing any secondary ignition or anything are you? (although ignition would likely show up at higher rpm too, unless charging system is weak) The vacuum jumps on that one cylinder only? Hell, I don't know, and your on the other side of the world. Let me know what you find.