Monday, 16 May 2011

DRM 200cc 3 cylinder

A 200cc racing motorcycle might sound unusual to some, but in Scotland and Ireland the 200cc class was a major racing category.
 The DRM 3 cylinder 200cc machine was a bike put together in 1976 by Davy Mitchell (DRM) to promote his motorcycle shop in Kirkcaldy. At this time Davy was selling Fahron water cooled kits for 125cc Yamaha twins. Davy had the idea of producing a three cylinder machine for the 200cc racing class using the 125cc twin as a basis. Yamaha themselves had made a 350cc 3 cylinder for Katayama and there were other home brewed 3 cylinder 'specials’ such as Tony Dawson's Scitsu and Ted Broad's machine.
 The base for the DRM was two Yamaha AS3 bottom ends. The crankshaft was made by Hugh Ward by assembling three pairs AS3 flywheels. Instead of the normal 180 degree firing order used in the twin,  Hugh modified the cranks so they were 120 degrees apart. This modification allowed the use of a Femsa ignition from a 500cc Kawasaki triple.
 The crankcases and gearbox for the DRM came from the Yamaha AS3. Once again one and a half AS3 cases were utilised.  

The water cooled cylinders for the DRM were made by Fahron engineering. The 200cc 3 cylinder was based on one of their 125cc twin kits but with an extra cylinder added. The three cylinders were cast together as one unit and then iron liners were fitted. Each cylinder used a separate cylinder chamber head. Each of these heads was then covered by a single top which ensured sealing for the coolant.  
Two DRM three cylinder engines were made, but only one was ever completed. The completed engine was housed in a Jack Machin frame (one of two similar frames made by Jack for a 125cc). The tube diameter of the frame was ¾” (the other frame used a tube diameter of 7/8”). A steel fabricated swinging arm was made by Fahron engineering. A Ducati front end and Yamaha rear brake was fitted.
The DRM was only raced on a few occasions due to reliability issues (big-end failure on one occasion). However, the DRM did what it was meant to – cause a stir and promote Davy Mitchell’s shop.

Update. There are a few new links concerning the DRM. The first is an account from Mike Brown who helped with the machining of the crankcases on the DRM:
The DRM has also been restored by Hugh Ward. Pictures of the machine can be found in this post:

1 comment:

  1. Tasty. The tank, the aircooled drums, and the stance all epitomize the late 60's/early 70's racing two-stroke look.