DRM 3 cylinder restored

Hugh Ward has recently restored the DRM and has kindly provided me some pictures. It certainly looks a lot smarter than the last time I saw it in the back of a van at Beveridge Park! Hugh has done a great job and the DRM looks stunning. I’ll let the pictures do the talking.

If more information on the DRM is required, here is the link to my original post:

DRM three cylinder

An account of the DRM 3 cylinder:

The post below is based on the words of Mike Brown who helped with the machining of the DRM:

"I was approached about modifying the crankcases and as you sit on the bike facing forward the right-hand most casing is as per original, the next one left has most of the careful machining which removed the crankcase area leaving the gearbox in tact with a flat face to butt against. The next crankcase part moving left was just a small crank case section generally about 35mm wide and finally the left-hand most casing contained a full crankcase but with the gearbox part all removed. The whole thing had to be lined up and holes bored for hollow dowels and long studs or with my engine, long specially made cap screws which held the crankcases together. Finally the mouths of the crankcase assembly were skimmed by removing about 0.2mm.”

“Davy had worked out that if we use 2 crankshaft centre sections of existing AS3 parts, we could seal the crankcases and due to the 6 splines that join the cranks together we would only require 2 crank halves to be modified. These were clocked up and the crank pin hole and the counter bore reinstated 120 degree round to the right with the original crankpin hole filled with a plug so as to help restore rotational balance. Once I had finished with the crank parts my good friend and colleague Hugh Ward reassembled the big end and rod assemblies by pressing them together and clocking them up true.”

“DRM racing sponsored a well experienced and able Scottish racer Mr Bill Milne and Bill had used an overbored /modified TA 125 in the 200cc class I think from memory it was 132cc all this work was done with Davy’s close links with Fahron engineering who produced very successful sets of water cooled barrels at that time. Fahron also produced the 3 cylinder barrels by making the cylinder pitch the same as the twin and machining the barrels and liners as they normally would.”

“Many other issues had to be addressed and Hugh would be able to provide this information but I do recall that initially ignition was with a Femsa unit. This machine was a very free revving unit but for various reasons it seemed to lack low down power in my view, probably due to porting, so performance was concentrated at the top end of the power range approaching 14,000rpm and the rider Kaj did run big end assemblies.”

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:

DRM account by Mike Brown

The DRM has also been restored by Hugh Ward. Pictures of the machine can be found in this post:

Restored DRM 3 cylinder