All About GT750 Gauges
Contributed by Allan Tucker
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All models of GT750 were fitted with gauge units made by Nippon Denso. Over the course of the GT750 production run, N-D supplied two main styles of gauges (plastic housed and metal housed) , which then included a number of variants as described further below.
1971 Domestic (Japan home market) and preproduction information is currently not available, nor is information available on the 'Patroller' Police bike. If you have any additional information, or think something is missing in any of the postings for the years listed below, please do let us know so we can research it and continue to improve its accuracy. Please include photos and/or copies of documentation about the item you wish to have added.
The first year of manufacture for the GT750 export models was the 1972 J model. For this year the gauges were comprised of a blue/black plastic textured upper case and curved acrylic lens integrated together and heat fused to a pressed form metal lower base. For a water tight seal the joint between the case and acrylic lens was done with a process that appears to be ultrasonically welded together, an advanced process for such an item of its time. There is a steel inner trim ring that is painted a teal colour to give the gauge a blue cast when illuminated. Its top edge is painted silver to reflect up into the edge of the lens giving the gauge a defining inner trim appearance along the lens to body junction.
On the lower portion of each gauge the bevel drive 'offset' gearbox for the cable was a separate piece attached to the lower metal case by three screws and these screws also hold the inner mechanism to the lower case as well. The plastic upper case was then heat sealed to the edge of the lower body to create a one piece gauge unit assembly and not designed to be taken apart after it was built. The gearbox protruding from the base of the large gauges has an offset cable spigot so the lower chrome under covers had this shape of hole as well to accommodate this feature. This gearbox unit is a very well made item and sealed to hold in grease. It is comprised of a pot metal body, an aluminium end cap, bronze bushings and a nylon plastic worm gear for quiet lubricated running against the steel gear of the internal case mechanism. The trip reel knob is an all plastic unit, fitting over a shouldered spigot glued to the plastic gauge body, it is very fragile and is usually broken on many units if they show up for sale or on used bikes. The internal mechanism parts for these gauges all have metal components except the odometer and trip reels, while later versions were fitted with plastic gears on the odometer reel versus the earlier ones with a metal gear.
Compared to the 1973 to 1977 model speedometers, the odometer reel on the 1972 gauges rotates in the opposite direction so that the order of the numbers are reversed. The trip reel however spins the same direction for all the years.
The faces for the gauges are finished in a semi black background with cream coloured segments and numerals. The tachometer has a red line area marked out in red segments instead of the cream coloured portions. Versions are known to exist in both plastic face and aluminium face for the large gauges. The plastic faces are made of a green plastic: on the front portion the face is painted black while the segments and numerals are raised sections of the face painted cream on the top edge. The light from the gauge bulbs shines through the numeral and segment portions only, giving the appearance of back lighting, as well as from a space between the edge of the face and the inner teal coloured bezel.
Versions were made for both metric and imperial speed registering. The metric speedometers have been seen in two versions so far but its possible more versions do exist. The tachometer had three warning lamps in the lower section for flasher (orange), high beam (red) and neutral lamp (green). The temperature gauge also has an inner face designed like the plastic faced version of the larger gauges but it never got the updated aluminium face of the later version J model large gauges.
The second year of manufacture for the GT750K included an update from the J models plastic cased gauges. The items carried over from the J model are the face plates, mounting screws, three warning lamps in the tachometer and the gauge mounting bracket.
However, for the 1973 K model came the use of new all metal upper gauge cases, which were finished in a very coarse textured matt black paint for the upper body portions. Sadly the factory didn't prime the metal cases beforehand so they suffered from 'rust through' very quickly, and all the metal gauges tend to take on a brown appearance over time. These new gauge units were sealed with a stainless steel compression band using a hidden inner channel rubber at the joint of the upper and lower halves. This design gave the gauges an attractive silver trim base ring feature when they were fitted onto the rubber base sitting in the mounting bracket. The upper cases now had a rubber seal to hold the 'real glass' lenses (the 1972 J lenses were plastic) which were slightly convex for a neat visual effect, and recessed below the upper metal housing edge for some protection from scuffs etc. A newly designed teal painted inner bezel was used with a revised upper edge that is rolled over and painted a cream white on the edge facing the glass.Although the large gauge needles look the same for all the years of 72 to 77, there are actually three different diameter armature shafts, so there are also three different sized needle bosses to match.
The lower case housing was also a newly designed steel pressing and carries a unique feature to the 1973 models whereby the mounting tab for the under plate screws is a single loop tab design. The offset gearbox was also discontinued and therefore a new centrally located cable spigot was adopted, this meant new under plates had to be made to accommodate this new design of cable spigot to the large gauges. The internal mechanisms for the large gauges were also new for 1973, and the odometer reels spun in the opposite direction compared to the 1972 versions - a feature carried on right up to the 1977 B models. The trip reset knob was also a new design and had an actual rubber sealing boot to prevent moisture from entering the speedometer units internals, a step forwards compared the 1972 J's delicate plastic shouldered design.
The internal mechanisms of the 1973 models gauges share the same pressed upper frame parts for the speedometer and tachometer unit, but the armature bells size is different, as are the related parts running adjacent to them. The shaft magnet and armature bell run at a bevelled angle against each other and are mounted in a metal base plate screwed to the upper pressing with four screws, this allows the cable spigot to run downwards at the required angle without the use of a separate bevel drive gearbox.
Recently seen as well are some complete sets of gauges in a brown background with a tachometer designed as the 1972 and 1973 versions. This appears to have been a re-release by the factory to satisfy market demand for earlier version gauges.. Notice the tachometer face has the warning lamps printed in full display wording above each lamp, and not simply a 'B' 'F' 'N' designation.
For the 1974 L model Buffalo, Suzuki decided to change a lot on the bike and with it came further gauge revisions as well. Most easily noticed is a new gauge mounting bracket which is a tad wider and more refined looking than the previous one. It brought the three tachometer mounted warning lamps into a central binnacle between the large gauges with a digital gear position indicator above them and integral switch key mounting mounted below. The little 'S' button was retained and doing duty to the left side of the switch to 'balance' the look in a separate mounting hole, a place where a speed warning lamp was fitted for certain markets. This hole's location has also been seen used for a cigarette lighter socket/DC power port, so its location has had its owners adaptations.
The binnacle, finished in a textured black plastic had a greenish square lens with a red LED underneath it, mounted centrally at the top and the three lamps spaced across just below. Aluminium plates glued to recesses in the binnacle with black screen printing were affixed and indicated 'gear position' and the related lamps features. High beam indication still used a red lamp which continued on in production until the late 1976 A models. The blue version came later in the 1977 B models.
The large gauges got another complete revision, new internal mechanisms were adopted over the one year 1973 versions with changes to the pressings and related parts, so its not just adding some pretty new faces. The large gauge faces were updated to a mid blue colour with pale blue markings and a new design layout, some are known to exist in the plastic faced version, yet most seen are the aluminium printed versions.The face plate screws were also updated to the integrated washer type if you care to look that closely. Models were available in both mph and km/h for the speedometer, so four versions of speedometer would have had to have been made, mph and km/h for the plastic faceplate version and mph and km/h for the aluminium faceplate version.
The temperature gauge unit again was as before internally, carried over from the original 1972 version with a plastic face, the difference being its face was now painted the mid blue colour instead of the black.
The cases themselves went through another visual change, with the textured paint on the upper cases changed to a slightly more subtle look, but this is a 'general' comment as the finish has been seen in so many textures from 1973 to 1977, however they all usually progressed to a lesser texture as the years went by. The lower pressings of the cases went to the double loop bracket for the under plate mounting points, and used fixing screws with a flat/cross head screw design to hold the inner mechanisms to the case. Curved glass lenses were again used on all three gauges and they definitely look very refined over the later plain flat ones.
For 1975 Suzuki made what appears at first to be no visible changes to the gauges, and they look the same as the 1974 models. However some subtle changes did happen during the 1975 model and these will be mentioned here for clarity.
Around the middle to later part of the 1975 model year, the temperature gauge face was updated to an aluminium printed type, finally ending the painted plastic face with the raised indicator markings. On the plastic face of the temperature gauge you will notice two raised dimples on either side of the central 'normal' mark indicator, obviously reference points of some sort for possibly testing/adjusting the gauges with voltage inputs at the factory during assembly. On the metal faced temperature gauges these areas were now indicated by small dots printed onto the face along with the other printed indicator marks. Along with this the 'Made in Japan' and 'ND' symbol were also printed onto the lower part of the gauge face where as previously on the plastic face it was raised but simply painted over.
When the temperature gauge got updated to the new aluminium face, all of the gauge glass lenses were also changed as well to plain flat glass, and sadly the curved glass lenses were discontinued. This was a mid to late 1975 design change, so unless someone can verify they have an all original late model M with earlier style gauges, its assumed as of this writing that all mid to late M models had the flat glass lenses and updated temperature gauges. The upper case textured paint was also further refined to be less textured and overall smoother in appearance.
For 1976 the gauges had no physical alterations done to them externally, everything looked the same, and rightly so they appear exactly as the late model year 1975 sets with the aluminium faced temperature gauge face. However, if you want to be picky, the textured paint on the case housing comes into play again and its been noted that some 1976 models had surface finishes of alternating texture.
Other than this external issue there were quite a few changes, but this time they took place INSIDE the gauges. Alterations were made to the design of the internal mechanism structures which was a complete departure from the previous types used. The lower spigot and its internal base housing the cable attaches to was also changed to an all pot metal casting unit, where as for 1973 through to 1975 it was a pot metal spigot with the inner base in pressed steel riveted to it. The 1976 speedometer units internal mechanism structure was also upgraded to a specific shape and differed quite a bit from the ones used in 1974 and 1975. The internal tachometer mechanism was also completely revamped in design with an additional diagonal support being added soon after the first ones were in use. This seemed to be a 'left off' item, as all the mechanisms have the place for the support so why they added it later after quite a few initial units were made is unknown. The tachometer damper chamber on the armature shaft also had a new snap-on plastic cap in place of the previous aluminium glued on caps that were in use since 1973. The spring boss on the armature shaft was also changed to a smaller and simpler type using a hex-less shape.
For a reference here, from 1974 onwards the mph speedometers used green coloured plastic gears and worm drive parts, while the km/h units use white components possibly for ease of visual identification in the factory. This colour difference also makes it easier to identify the white parts which have a higher ratio, as in less teeth on them. To add some confusion to this, the 1972 and 1973 speedometers did not follow this coloured plastic rule so its a whole different story on those 'one year' specific units.
Suzuki decided to revamp the 1977 gauges on many of their models, possibly more so for the NEW GS line-up of four strokes they were working on bringing to the world market, and so out went the old previous black faced and mid blue background colour of gauges.
New for 1977 was the use of medium brown faced gauges with white/cream markings - the GT750 B model was one of the first bikes still in the current line-up to get these gauges. It seems counter productive to make a set of 'one year' gauges at the end of a models lifespan but the powers that be, had spoken, so it was done for the Buffalo.
Some may disagree about the brown colour but they looked a bit more refined, and updated the bikes appearance, especially when it sat next to the New GS 750 models on the showroom floor. It's no secret Buffalo sales were dying, so they used a lot of trim parts from the new GS 750 model to modernise the bikes look in a final attempt to boost sales. The speedometers were again made available in metric and imperial measurements, since the US market was and still is a non metric country. Dual scale speedometers with primary mph were also made available for the UK market and possibly others, these versions have been seen with a noticeably darker brown background as well. These dual scale units have the primary speed markings in white/cream on the outside with the lighter orange/brown lesser scale inside.
For the 1977 model gauges the internal parts/mechanisms were already updated in 1976 so they decided to leave them as they were for the final year. The parts such as the under covers and bracketing remained the same as well for common use of those items, again, there appears to be no need to fiddle with alterations. However they just could not be satisfied with them and something had to be done, so what was it? Well at first glance the binnacle lens for the high beam was changed from red to a blue one and you'd think that's it, but look closely, the lens for the gear display was also changed to a mauve over the previous greenish one as well. That's not all that changed in this area, they also altered the LED display unit inside the binnacle as well, all 1977s have a black plastic framed LED display unit with a white "8" coloured display, while 1974 to 1976 models carry a red framed unit or different style of red "8" display unit. These different red "8" display units carry a black foil backed decal stuck to its surrounding area on the display front edge. This means there are three different LED displays for the bikes made over the years of 1974 to 1977. Along with this triple change of a part, they also flipped the wiring pattern around on the display, so on some the wire jacket colours read the opposite from left to right as they are attached to the base bracket. Why they did this amount of alteration to a small part is possibly the vendor supplying what they could in job lots, but speculation is a lovely thing when there is no way to confirm their reasoning 30 plus years on.