Intake valve clearances

[randy]

While looking through my gen-u-wine Yamaha service manual, I came upon a supplement for the 80G that says the intake valve clearance was changed that year to "reduce engine noise".

The clearance was reduced to .11-.15mm vs. the previous year's .16-.20mm. I compared the cam lobe specs and they're the same for 79 & 80.

That being said, is it OK to run the tighter intake clearance on all (XS) engines, and other than "reducing engine noise", would there be any other benefit?

[mro]

The clearance was reduced to .11-.15mm vs. the previous year's .16-.20mm. I compared the cam lobe specs and they're the same for 79 & 80.

79's cam is about one shim size taller than 80's (.005mm) and 79 intake valve is 2 mm smaller.

Don't know about noise reduction as it seems on my 80G that most noise comes from the exhaust which clearances are same for all years.

Tighter tolerances (increase valve opening) should increase performance. Just don't think would make a noticeable difference on a stock engine.


mro