I was going to take the gear case off on my sons 250 this winter to check it out but manly to change the oil sinces there's really no other way to get it out . Instead I took some fish filter air hose and ran some wire in it and I was able to snake it to the bottom of the case then I pulled the wire out and hook up my mighty vac brake bleeder to it he hose . It took a little while but I got it all out then I was able to pull the hose right out . By the look of the oil I think it's the first time it was changed . I put a magnet in the oil and I found a little metal shavings not much I figure for a machine that's over 36 years old its not bad .

I recommend a gear lube with gear climbing additive. People have a million different opinions on which oil to run, Honda recommends 10w-40, others say different.