1976 RM125A

Thew 76 crank was a one year deal I believe with a larger diameter piston pin than the other years. My brother may still have a NOS crank for that. We ended up with one by mistake, was supposed to be a 77.

Newmanns crank would be best as it is most likely a later generation part, the early ones
tended to break the LH side of the crank at the main bearing. They had a bulletin showing
the new LH web available separately if needed, I believe they just used a different tempering
process on the affected area. If you have to work with the standard crank check with Phil at
http://www.crankworks.com/ he often compares con rod dimensions to do a direct fit or if
nothing works one that may need to run a spacer plate which Cometic can do as a special
order.

Be sure and check the intake manifold as the bolts were really too far apart to make the surface
seal, check it with a thin feeler gauge about 2-.003" to see if it will slide between manifold and
the cylinder. Usually a sealer like three bond 1104 will make it happy, sometimes you have to
make a gasket to fix. Some good news is the 76 used the same case reed as the 250/370
which can be modified into a 4 petal reed that gives a nice boost of power......pretty much through
the entire range.

If you flip the reed block upside down you will see a void under the gasket area, there is an angle
that if you envisioned the cylinder side of the block missing except for the angled area it would
make a short lopsided V similar to a normal V reed block. It takes a reed about half the length
of a stock one but worth the drilling, machining, tapping etc.-good luck!

If you have trouble with understanding or doing the work PM me and
we can certainly work it out-R

What you can do is go to a bearing supply house and see if you can buy better quality (Hi RPM) bearings.