91 Moto 4 foot shifter sticking

[kenikas]

We've run into another strange difficulty in our resurrection of our 91 Moto 4 250 basket case. It's running great now, and with the new cylinder & piston we're thrilled with the power this thing has! We searched high and low for a replacement drive shaft boot, but since this style was only used for a couple of years, they are pretty much unobtainium at this point 😥. I was able to fabricate one out of a truck C V joint flexboot that seems to be working well, I'll post a write up on it with pic's when I a few spare minutes.  But back to the problem I'm having with the foot shifter, it seems to shift pretty well going up through the gears and goes into all of them, but going back down we have a problem. The foot shift lever sticks down and won't return to the center position until you reach down and bump it up with your toe. It sometimes sticks up when upshifting too, but that's fairly rare. I'm running a straight 40 wt. mineral oil to help break in the new piston rings and flush any crud out of the engine, and plan to change it and the filter in a couple of days but don't think that would effect it. We did have the engine right side cover and spacer off (clutch side ) and had the shift arm, guides & pawl off, but I'm sure I got it all back together right.

Any Ideas would be appreciated.

[Mech]

Is the shaft a bit tight in the housing ? Gear-shafts get bent sometimes... or it could be an end-float issue.. gasket missing or wrong shim. That would have changed when you pulled the cover and so could have been missed.

If the shaft is free then you'd think the return spring for the shaft is not working..

 

[kenikas]

Thanks for the ideas Mech, we got looking a bit closer and I think you're probably right on with the bent shaft theory.  This one comes out of the crankcase, then goes through an extension of the casting on the generator cover, and it's been well and truly "Bubba'ed" at sometime in the past. The foot lever has been welded on to the end of the shaft! So the only way I can see to properly fix it would be to cut this shaft and replace it and the foot lever, but of course the shaft is a discontinued part, and so far no luck finding a used one 😥. So I think I'll most likely fabricate some brackets to attach some "helper" springs to assist the lever back to the center position, and just ride it.

[Mech]

Well if the weld is on the end of the shaft, you could probably grind it back a little/flush, then use a screwdriver to force the lever's clamping bit apart slightly, and by wriggling the lever, break the rest of the weld. That generally gets them off. The shaft is possibly damaged on it's splines though and may need replacing, but, some people reach for the welder far too quickly, and I've fixed old welded lever/shaft problems before. A small triangle file, and a new bolt and things might be reusable.

Even if you do have to weld it back on again, if getting it off helps diagnose/fix the problem, that's all we need.