Welcome to the RM Rescue Engineering website, dedicated to preserving twin shock Suzuki RMs, especially RM125M/A/B/C/N/T (1975 through 1980). I mostly do software engineering work which supports this RM125 thing :)
PDI RM125B Expansion Chamber
Picture of PDI versus stock pipes side by side. (480K)
Thor Swingarms
Picture of two Thor swingarms, top is for an RM250A/B with 17-1/2" shocks, the one at bottom is for an RM125A/B/C with stock 14-3/4" shocks. (145K)
Left side picture mostly of the RM125A/B/C swingarm for stock 14-3/4" length shocks. (145K)
Another picture of the RM125A/B/C swingarm for stock 14-3/4" length shocks, but in the sun. (180K)
Left side picture mostly of the RM250A/B swingarm for 17-1/2" length shocks. (145K)
Collection of measurements from RM125A/B/C/N/T stock swingarms and the Thor swingarm with stock length shocks. (2K)
Observations: The 250A/B swingarm is the same length as the 125A/B/C swingarm. The rear opening on the RM250A/B swingarm is about 0.125 inches wider than the rear opening on the RM125A/B/C swingarm.
Chain tensioner mounting points match up.
Pivot tube is about 0.125 inches narrower on the RM250A/B versus the RM125A/B/C swingarm. Check http://www.alpha-sports.com for the RM250A/B bearing setup as the RM250A/B specifies a narrow thrust bearing to go on either side of the pivot tube. No longer available from Suzuki, they last priced at about $30 each! The RM250A/B swingarm uses needle bearings while the RM125A/B used bushings and RM125C used needle bearings (interchangeable with the RM125A/B). The RM250A/B swingarm needle bearings look massive compared to the RM125C needle bearings. The pivot tube on the RM250A/B arm is almost 0.250 inches larger in diameter than the RM125A/B/C pivot tube. The RM250A/B inner races are still available and can then be bushed to match the diameter of the smaller RM125A/B/C swingarm pivot bolt.
The chain adjusters on the RM250A/B swingarm have machined steel spacers that fit into the chain adjusters then the axle fits into the spacers, which makes mounting the rear wheel much easier than the the RM125A/B/C version where the axle goes directly into the chain adjusters which is awkward to work with as the chain adjusters flex a great deal.
So, it does appear the RM250A/B swingarm will work just fine on an RM125A/B/C, other than requiring some judicious shimming.
Contact Info:
RM Rescue Engineering / Phil Fuhlman
P.O. Box 68
Exeland, WI 54835
715-943-3230
Email
Last updated: 2007-15-November
