I was wondering how to measure freeplay of the butterflies on the exhaust valve shaft. There is nothing in the manual, so I looked in the NSR125 manual and it says "1 mm max. at the tip".

I found a setup which I think is what Honda meant:



3 of the four butterflies move by 0.75 mm, one by 0.35 mm (@46,000 km)

Has anyone ever cared to measure the freeplay of used or new butterflies? If so, what have you found out?

And: the shafts have a lot of play on the outer bearing. Is this ok? Will this reduce once the head heats up? Has anyone ever fixed that, e.g. with a bronze bushing?

gepe

There is no bearing inside the barrel , it is a steel bush .

Wrong word?
I thought "bearing" identfies any kind of "a machine part in which another part turns or slides"(Merriam-Webster), not just ball bearings or needle bearings.

So you are under the impression, there is a steel bushing? I thought it was just a boring in the aluminium. I will have to wait until my cylinders return to check that.