85 Honda ATC 125M transmission noise / shifting problems

[cbuttre835]

Howdy all, been a while, first post on the new site.

Have spent a while reading all the 125M transmission problem threads, and can't find one that matches my situation exactly.

Just cleaned the carb on a "barn find" 85 125M that had been sitting for 8-10 years. Starts first crank and runs like a champ. No smoke (except a little black puff when you cod on it). It had an oil-like substance in the crankcase, ran it 15 min or so to get it hot, now it is filled with 0W-40 synthetic ATV oil (Amsoil). Blackest oil you ever saw drained out.

I rode it around the neighborhood on the new oil and it shifts funny - in particular it doesn't like third and fourth gear.

I read a little on it, and went back to the shop. With it sitting and idling, I can hear the transmission "freewheeling" - kind of a chattering noise. Kind of like the noise you get from the subtransmission, if you swap the subtransmission from low to high with the main trans in gear, and it is just barely chattering on the gear teeth before you engage it fully. Put it in first, the noise stops.

It'll step through first and second every time; third and fourth some of the time. I'm basing a "good shift" on the position of the neutral indicator; I made me some marks to be able to tell. Sometimes it'll stop in third enough to move (but will jump on out if you stab the throttle), sometimes it's like a "false neutral" there - but the "freewheeling" sound doesn't come back; till you ease on the shifter, then the gears will grind and it'll stop again.

I'm thinking it's the shift drum stopper like mentioned in the other threads - that my "freewheeling" transmission sound is actually a slight chatter of first gear trying to mesh - if it didn't have the shift issues in 3rd - 4th I'd suspect a bearing, but the shift issues seem to stem from the shift drum stopper.

Now, the question: What do I look for, on that shift drum stopper, (or anything else) when I pull the right side clutch cover? That is, how do I know if it's "bad"? I hate to buy one, and that NOT be it... I'd rather evolve into a mechanic, instead of just being a parts swapper.

All help appreciated.

[Howdy]

It could very well be a wore out or busted shifting fork. Not a easy fix by any standards, but still doable.
Howdy