Tuesday, August 14, 2012

Pre-Unit Triple Clamps

I have a set of triple clamps off a '56 Pre-Unit. Starting in 1960 with the release of the Duplex frame ('60-'62) the built-in rake (about 3 degrees) was removed from the Pre-Unit yokes. I spent a little time trying to figure out the visual differences between the early and post-Duplex yokes. The bottom is easy, assuming they haven't been cut up. The early lower yokes have the prominently protruding "wing" fork stops.

Triumph appears to have used three different part numbers for these bottom yokes 1950-1959 and the differences are very subtle. 1950-1954 had 5/16" pinch bolt holes, '55-'57 3/8" pinch bolts and the 1958-1959 models have a slot in the steering stem for a fork lock on the right side of the steering head.

The post-Duplex lower has noticeably smaller fork stops. You'll also notice no forward "lean" in the stem if you set the clamp on a flat surface like a table.

The top clamp seems a little more mysterious. I noticed Paul from Show and Go had pondered this same problem at one point. In '56 part number according to '56 Part Book 97-0663A (H663A) was used. See an example of 97-0663A pictured blow:

These photos match visually what I have from an original '56 bike.

The 1961 Parts Book lists 97-1108 (H1108). See an example below. I assume the rake is different between the two parts but visually they seem to look identical. I expected there to be an obvious casting difference as described in the Show and Go post but I'm now starting to suspect it's not quite so clear cut.

If you are aware of any other tell-tale identifiers I love your advice. Incidentally I'm interested in locating the '61 pieces (97-1108 & 97-1283).

No comments: