What is the purpose of the sight glass on the LT250R and LT500R? I understand that it has something to do with the power valve, but why is it necissary for visual inspection?

Another question, what is the fuction of the set-screw on the underside of the sight glass? Is this the stop adjustment for the power valve? On my 500 the set screw is hanging out 3/4". I'm thinking that the original fell out and somebody put a long set-screw in it's place or is the original actually that long and it is backing out.

 

Im not sure about the set screw but the site glass is to firstly show its operational and secondly to enable you to adjust it. You hook up a tachometer to read the revs and see when the powervalve is activated at what revs.