I do wonder if a transmission breather is NEEDED on the NSR250.
Can anyone explain why it is needed?
Is there any way (other than atmospheric pressure and altitude combined with running/storage temperatures) that can cause significant pressure or vacuum?

Of course, in a four stroke (especially big singles) where the crankcase and transmission share the same volume, there is a lot of pumping going on due to the piston movement, and blow-by past the rings can pressurise the crankcase, but this is not the case in the NSR250.

Do atmospheric/operational temperature/pressure differences actually necessitate a breather tube?

Is it just the temperature changes observed between running the bike in the Saharan summer and then being stored in Northern Finland over winter that necessitate the use of a transmission breather?
OK, that is an extreme example, but you get the idea, right?

Is the possibility of developing a leak between the crankcase volume and the transmission volume enough to warrant a transmission breather on the NSR250?

Just plain curious. That's all.

I assume I am missing something here. But, someone can hopefully explain what.
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