Time to get the switch gear sorted, and of course nothing is straight forward. The 1972 model GT750 used a one year only set of switches, and good working examples are difficult to locate. As well, internally the left side switch is quite different from later
models as it has individual block switch modules for each function.
I actually just had one left switch for the GT750 and a second left switch that was from either a T500 or a T350 of the same year as it was unpainted aluminium. The GT750 switch gear was originally painted in gloss black. This unknown left switch also had the connector block cut off and so needed new wiring and black plastic sleeving, but otherwise looked complete. As can be seen in the lower part of the photo (just click to see a larger version) . it was also wired differently from the GT750 version seen toward the top of the photo, having different colour codes and termination points on the headlamp switch modules internally.
Disassembly of these switches is not for the faint of heart as there are a lot of really small components inside them: small springs, even smaller steel balls, little brass slider contacts and little tiny screws which seem to disappear as if by magic into the darkest deepest recesses of your work area, never to be seen again ! My first step then, was to clean the the switch blocks with electrical contact spray cleaner without attempting to disassemble the individual component parts, temporarily reconnect nine-pin connector blocks and then check with an ohm meter to see whether they worked at all. A couple of the switches did not work at all on the silver left switch and so then needed careful total disassembly to properly clean them. During reassembly I lubed the interior contacts with dielectric grease, and also did so for the modules I didn’t disassemble.
When wired up temporarily to the bike, and with the power on, they now all worked reliably with the exception of the horn button on the ‘real’ original GT750 switch. A closer examination showed that the circuit board was cracked, and so when pressing the horn button, the flexing of the board caused intermittent contact. This early switch was also a different design than later ones and is actually missing the lower metal clamp that provides support for the board to keep it from flexing. You can see the early switch (left) and a later one (right) in the photo to the left. I’m not sure when the change was made, but it would have been after frame 16153. The left switch was completely redesigned for 1973 and later models using a round housing similar in shape to that already used on the right side, and the headlamp on/off and high/low beam switch was simplified. The combination horn and turn signal module however used in the newer left switches was the same up until sometime in 1974. Luckily I had a later style scrap left switch and so was able to salvage a working horn/signal switch module.
The internals for the right switch gear are pretty much unchanged through the course of GT750 production.
With the switch modules sorted out, I then stripped the switch cases down for painting. When SWMBO’d was out shopping, I cured the painted cases in our counter top toaster oven for an hour. 🙂 Once they had cooled down, I added the orange paint (I use Testors Tangerine 1126TT) for the lettering using the ‘dab and wipe’ method and re-installed the internals, using new black sleeving and connector blocks that I buy from Vintage Connections in the USA.
The final result looks pretty good, and also works which is always a bonus ! On to the final finishing steps as I get closer to seeing whether the engine will fire up ! And If you are interested in all the different switch gear used during the GT750 production, they are covered in ‘The Field Guide to the GT750’ which you can find at this link.