I<3Dirt

Member
Feb 3, 2007
49
0
Picked up an '88 RM125 about a week ago and I'm having some trouble with the bottom end. I bought it with the the clutch and all gears in the right hand side case disassembled.
The internals in the bottom end were completely rebuilt by a well known local shop, apparently. It has a hot rods connecting rod and had a tag tied to it when I picked it up so I believed him.. now I'm not so sure.

Anyways, after assembling and then disassembling it again, I can only get it to turn over one revolution and then it stops, going back or forward. Even with a wrench on the crank bolt, it only turns over one revolution and then acts as if theres a spring inside stopping it. It seems like I could force it past but I don't want to snap anything inside..
I also can't shift throughout the gears at this point.
I know that's a little vague, but Any ideas?
 

I<3Dirt

Member
Feb 3, 2007
49
0
So pretty much scratch that post... It turns over fine with the crank bolt, BUT if I try to turn it over using the transmission shaft, I only get one revolution and then it stops again. I don't really know much about bottom ends so this, and the non-shifting problem have me pretty stumped. It feels as if it's stuck between gears, as in when you have to roll the bike to get it into neutral sort of thing.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Remove the clutch for plenty of room. Remove the shift lever and shaft. Inspect that the shifter star is installed properly, and there should be 2 spring loaded detentes that hold the drum in position. Think about which way the shift shaft turns the star and drum, rotating 1 of the trans shafts will help to get it in neutral. Hold both shafts, they should turn separately. At this point make sure the star is centered toward the shift shaft, and install the forks on the shaft centered with the forks on the star. The case and shift lever hold the shaft in place, it only needs to move an 1/8" and it will not be engaged. Sure hope you have a shop manual, if you know you're way around, a parts micro fiche can help. Vintage Bob
 

I<3Dirt

Member
Feb 3, 2007
49
0
Thanks a lot for the info, turns out I tightened down the pawls too much and it wasn't allowing any movement to shift.
I do have a manual as well but I apparently skimmed right over the spacers needed for the pawls on the diagram.
Thanks again.
 

FLYING.FINN

Member
Mar 3, 2010
26
0
HAPPY TO HEAR THAT YOU GOT YOUR GEARBOX FIGURED OUT. I had a 1982 RM-125...best bike I ever owned,..I've also riden a 1987 model...lots of juice...have fun with it.
 

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