Gearbox oil 10 40?
 

I'm going to replace my gearbox oil this weekend, I have some castrol R1 10 40 left over from my 4 strokes, is this a bit to thick to use? If not I will go and pick some mtx up

10-40 is no problem

This is what I use its very good

I changed the oil, clutch still squeals a bit it you take off from a standing start but not as bad as before

If the oil was very dirty I would change again just to make sure all is flushed out