[IDoDirt]

DO NOT try to adjust your valves to the minimum gap (o.002 in) The minimum gap means that any wear or extra heat on the head can reduce your valve tappet clearance to the point that you could burn your valve seats - and that means a new head!

I don't agree with this statement.

The manual gives a specification of 0.05mm. It doesn't give a +- tollerance, just the spec. When your engine warms up, the gap between the top of the valve stem and the tappet adjuster doesn't get smaller, it gets larger. I just adjusted my valves today and confirmed it. The engine cooled overnight and this am was the head was 68 degrees F. I adjusted to 0.05mm with slight drag. (I will say that whoever did the valves at the 600 mile check up either didn't do it or didn't do it right. I could easily get a .15mm feeler gauge in all the gaps.) Anyway, I put it back together enough to run the bike with an external tank attached and ran it for about 10 minutes. The heads were now reading about 195 degrees F. I turned it off, removed the valve cover and checked the clearances again. I could easily get a .07mm gauge in the gap. Aluminum heads expand more than the steel valve does, which effectively pulls the valve further away from the tappet. If you don't believe this, check for yourself. I think that the real important thing to do is make sure the engine has completely cooled before making your adjustments.

 

[IDoDirt]

No....read the original post:

Before adjustment cold engine- .15mm gap
After adjustment cold engine - .05mm gap
After adjustment hot engine - .07mm gap

Gap increased .02mm with head at operating temp.

Different metals expand at different rates due to temperature....aluminum expands more than steel for instance.

Differential expansion gives more gap in hot engine

Cookie

Yes, exactly. When I worked on cars with cast iron blocks it was a different story, the gap would get tighter. Aluminum engines are a different story.

When I did the adjustments, the .05mm had slight drag. After I set them, I rotated the crankshaft through several turns and rechecked to be sure I had them correct. After warming up the engine, I could easlily slide a .07mm gauge into the gap. No drag on any of them. I didn't keep inserting larger ones to see how much it had expanded. It was enough just to know that it did get larger.