Vintage Dirt Bike Q & A

Greetings,

I replaced a third gear in my 1979 CR125 and rebuilt the tranny, top end, and carb. The bike runs great, but I fear I've missed something with the tranny.

The bike shifts and rides through all gears fine, but when I get into first gear, the shifter still pushes down (obviously not shifting or anything, just annoying). I hadn't ridden this bike in quite some time, but if I remember correctly the shift lever/shaft should stop at first gear. So, I can downshift 5 times, but then it will act like it keeps downshifting.

Could this be a problem with the external shift mechanism? I really don't want to have to open the case back up, but can't figure out what should mechanically stop the shift shaft when in first. Hopefully it's something simple...

Thanks in advance.
-Pat-

Hi Pat,

There could be several things causing this problem:

1: the drum shifter and the shift spindle are not aligned...there are dots on both and should be aligned when in neutral.
2: The shift spindle adjustment is not set correctly (not allowing the spindle to move the drum shifter clockwise enough to where the spindle returns locking the pawls into their "catch" positions)
3: The spindle, shifter, pawls or associated parts are worn out (however, this is not common with this model CR's)

This might seem like a small problem now, but it will turn into damaged gears if the bike road in this condition for an extended period of time; the engagement dogs are not allowing the gears to "lock-in" and will cause premature ware on 2nd Counter and 6th Main.

Hope this helps,
Robert