Valve shim

Got my valve clearance measurements and am ready to swap the shims.

just curious if I should go the next size down if the measurements are super close between needing a 270 or 265?
Ik “in spec is in spec” but if it’s .0015 of a difference, would going the next side down be smart way to go? Less time between adjustments?

thanks for any input

 

I generally tend to set them on the loose side - ie, when between sizes, go for the thinner shim. *

That way, the checking interval is extended, or if it slips your memory, you've saved yourself from future tight valves.
A lot depends on how the bike is used - long journeys at constant speeds don't cause much wear, whereas short journeys up and down the gearbox mean that checking intervals should be closer to the book figure.

*Not sure about Yamaha, but Suzuki had some factory shims that were incremental sizes, just to get the clearances right by the book.
IE, in your example, there might be a 267 used instead.

 

In spec is in spec.
Out of spec is out of spec.

 

Thank you both

 

The increments for the xj airheads is by 5’s.... 250, 255, 260, 265, Etc......
the MaximX has a bunch more incremental sizes, but they are a different diameter and shape... totally not useable for the airheads

 

And, of course, the difference between consecutive shim sizes (0.05mm) is the same as the width of the "in-spec" range (for example intake clearance on my Maxim is specified as > 0.10mm and ≤ 0.15mm). So you really don't have a lot of choice as far as "shimming a bit loose" goes; there will be only one shim size that lands the clearance in the specified range.

 

When I ordered shims for the X, I ordered from Australia. https://www.precisionshims.com.au/products/lap
Their increments are in .01 MM.

 

In-spec is in-spec