Frame Differences – Who Really Cares ?

Probably no one cares, but what the heck  – winters are long up here and sometimes stuff like this helps to pass the time !

Late in 2009 I needed to do a bit of clean-up and pick which frame I was going to use for the 1973 GT750 project, and I noticed a funny thing – even though there is just one frame part number listed for 1973, there are actually a  surprising number of little differences between the physical build of the Suzuki frames over the 1972/1973 period. This will most probably make most reader’s eyes glaze over, but if you want something to read as an aid to getting to sleep faster, then read on – of course if you are a slightly manic old bike re-builder then perhaps this will be interesting – in either case, you’ve been warned !

For a really good over view of the GT750 model’s evolution you can look no further than Jarmo Haapmaki’s web site which is a gold mine of great information – however if you really want specific, detailed engineering information – information on very specific design differences to help you determine originality – you have to look elsewhere. The part manuals are a start, and there is only one part number listed for the GT750 1972/1973 model year frames. However when looking at several frames closely, there are various obvious differences, so the only really solid source of information is the actual frames themselves. Fortunately, the local Loyal Order of Water Buffaloes here in Calgary has a good choice of frames available to examine !

Here is what I’ve noticed so far – and while I suppose it could be specific to bikes sold in North America, I suspect these differences may apply to the global production. In some cases I’ve provided links to photos:

  • the engine mounting lugs on the lower, front frame cradles in early frame builds (late 1971/early 1972) have different fittings than on frames made up to perhaps March 1972 – they almost appear  cast
  • around July 1972 for what were to become 1973 model year bikes,  the right side driver’s foot-peg mount was changed from the single post notched design mounted on the rear brake pivot as used in 1972, to being a  single bolt footpeg mount fitting on the frame , while retaining the small ribbed rubber cover design used in 1972
  • the rear turn signal mounts were changed from a welded tube mounting to be a bracket (part 41640-33001). A further change was made sometime around October of 1972 and the side stand mount was changed from a two bolt mount to a three bolt mount.
    • early build 1973 model year bikes then are easy to pick out, as they had 2 bolt side stands – later in the model year production run they switched over to three bolt side stands – yes I know you can also check the serial numbers, but not everyone carries a list of serial numbers around with them all the time …..
  • 1973 also had two different styles of radiator side covers – while they appear to be the same externally having a chrome finish, on the inside the early production model mounting fittings are shorter than on later ones – early have the same height mounting post as used on the 1972 model covers which were painted, and the posts are about 4 mm (about an 1/8th inch) ‘taller’ by late in the 1973 model run. I’m going to have a set re-metallised later this year by an outfit in BC,  and happened across this while I was sorting through different sets trying to find good candidates to be re-done and noticed they were not all the same. I suspect the added length may have been added to allow a wider air gap for cooling, as several of the samples I have show signs of heat damage at the four corners where the plastic cover would have been closest to the metal radiator.

What’s the point ? Well if you are really interested in knowing whether your bike is original, and/or possibly rare then it is these little subtleties that are worth looking for – otherwise I guess they are just potential trivia questions to be debated after a few beers at your local club meet 🙂

Next – some bling !

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