Technical Q and A for classic motorcycle maintenance and repair.
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Triumph valve adjustment
Q: I ride a 1971 Triumph TR6 650. The manual says to set the valves cold, with the intake set at 0.002 inch and the exhaust at 0.004 inch. My question is, it’s hard reaching in to set the valves and I’ve always had a hard time getting those tight clearances right. I’ve always heard that valve clearances tighten up as an engine warms up, so I’ve been in the habit of setting them loose, with the intake at 0.008 and the exhaust at 0.010. A friend of mine says this is a bad idea, that I’m running the risk of burning the valves. It seems to run just fine, and I don’t notice that it’s any louder than other 650s I’ve heard running. So my question is, am I risking damage to my engine setting the valves this way? If there is a risk, what is it, or is this just an old wives’ tale? - George/Yellowknife, NT, Canada
A: I know exactly what you mean about the difficulty in reaching the valves on Triumph vertical twins. No, you don’t run the risk of burning valves by running loose valve tolerances. Loose tolerances actually allow the valve to stay seated longer, allowing more heat to transfer from the valve to the seat. What you do give up is flow and some high end power. That said, 0.008 and 0.010 is a little loose; too much clearance and you risk wear to the cam face, rocker arm and valve tip as these parts slam into each other at higher RPMs. I’d be more comfortable with 0.004 and 0.006.