1992 Suzuki LT 250R glass window

i just bought a 250r 1992 quadracer i have a clear glass window on the side and i dont know what its for but it is empty.can anyone tell me what its for?

Welcome to the site, that is a great machine you have IMO. My father had one when I was young, I loved that thing. That window ont he side of your motor is a sight glass so you can visually monitor the oil level in your tranny, sounds like you need to add some oil.

yes it is for your oil mine is for the trans and motor make sure to fill it b4 you ride it

After thinking about this, I think that motor has a sight glass over the powervavle, and I don't think that there is one for the tranny oil. I believe the window is there so you can visually check to see if the powervalve is working. It has been a long time since we had ours, so I don't remember exactly. Maybe Scott will see this thread and chime in, he rides an old Quadracer too.

I do have the sight glass but I can't remember now where it is I will look tonight if I can and let you know. I believe DD is right.

I cannot locate my manual right now but it appears that the sight glass is for exhaust valve.

I found this on another forum:

at idle, the valve should be open, through the sight glass the arm should be down.
once the RPMs increase enough to close it, the arm goes up(rod pushes it up.)
the spring adds just a slight amount of additional pressure and allows you to tune the RPM the valve closes by how far you turn the knob... a significant change can be had with only +/- 1/4 turn from 360CCW.