1972 Suzuki GT750J Frame, Suspension, Gauges, Tin and Trim
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The frame used on the GT750 went through quite a number of changes between 1971 and 1974 when it was 'finalised'. Specific to the 1972J series (part number 41100-31601-019) are:
The rear axle stop bolt cut-out on the swing arm is specific to the J and K models ( 61101-31806-019) having a half-round bolt cut-out shape. Later models were cut straight across (61100-31830-019).
The swing arm bushes for the 'J' and perhaps also early 'K' were steel. These changed to the fibre type during the 'K' production.
The rear tail light is a two bulb unit, and the tail light mounting bracket that holds the rear tail light, and which bolts to the rear fender is specific to 1972/1973 in that the tail light mount holes are set differently to later models (refer also to this section). There was no separate part number for the mounting bracket, as the tail light and bracket was sold as a sub-system.
The rear passenger foot pegs (43600-31000) bolted through and doubled as the rear exhaust pipe hanger bolts.
The 'J' right front driver's foot peg is mounted on the end of the rear brake pivot shaft. The driver foot peg rubbers covers are small ribbed in both 1972 and 1973, changing to the large block style in 1974 and onwards.
The foot peg was relocated for the 'K' model. To the right both types are shown - the unpainted 'J' right side foot peg is on top of a 'K' type peg
There is very little frame gusseting as compared to later models at the point where the rear engine cradle and swing arm mount plate and the frame extensions for the rear passenger foot peg and exhaust hangers connect.
The 'J' right front driver's foot peg is mounted on the end of the rear brake pivot shaft. The driver foot peg rubbers covers are small ribbed in both 1972 and 1973, changing to the large block style in 1974 and onwards.
The foot peg was relocated for the 'K' model. To the right both types are shown - the unpainted 'J' right side foot peg is on top of a 'K' type peg
The side stand used a two bolt mounting as can be seen in the upper right side of the photo to the right. This was changed to a three bolt mount during the 1973 model year.
Early J frames also are missing a cross brace under the cooling fan as can be seen to the right - this appears to have been added around frame 22007.
The left and right ends of the radiator were covered in plastic, painted end caps matching the main body colour as seen in the photo to the right.
There was no grill covering the front of the radiator (although one was offered as an optional extra, and after market and dealer installed grills were common), and the radiator crash bar was common to both the 1972 and 1973 models having two bump bars extending vertically located at about the 1/5 and 4/5ths position.
Note also there was a change to the radiator crash bar with the early 'J' models. Prior to at least frame number 18515, and possibly later there was no dent in the front lower centre of the bar. Early style shown in the upper photo to the right, later style in the lower photo.
The exhaust system had black conical tips on the ends, and cross over coupler pipes (ETCS) connecting the three downpipes together at the front.
The chain guard cover was black plastic (part number 61311-33000-019)
The inner rear fender was plastic (part number 63112-31000) and bolted to the rear chromed fender on the upper fender side under the seat using parts 4, 5, 6 and 7 per the diagram to the right.
Both J and K models used an electrical panel having no cutout for locking type connectors which were introduced for the 1974 L series.
Both the 1972 and 1973 models used a black rubber two fuse holder for the spare fuses. This fitted onto the tab on the electrical connector panel. The same part (36790-31000) was also used on the 1973 GT185, and the 1972 through 1974 GT380 and GT550.
All markets (Japan, North America and E1 General Export) appear to have used the same handlebars, although lower bars were often fitted by dealers in Europe. The stock bar part number is 56111-31000.
The left set of handle bar switche on the E1 General Export version was specific to the 1972J having a 'side to side' high/low/off headlamp switch mounted above the turn signal 'left/right' switch, and
being part number 57700-31010 (and later 57700-31011) - both using half round switch heads (57742-26010). Below the indicator switch was the horn button and below that the 'pass' or 'flash' button. The right side handle bar switch set was shared across the 1972 and 1973 model years having a pebbled surface on the three flat areas of the engine kill switch, the engine start button and the flat area in between. The right hand switch gear was part 57100-31830. Refer to the Country Specific section for other variations.
The front fork ears did not have a separate hole for the turn signal stalks - this appeared early in the 1973 model year. The turn signal mount also served as the head lamp bucket connector bolt
Specific to the 1972, and to some early 1973 K models, is the front turn signal stalk which is drilled all the way through to fully hide the wire to the lamp, and is quite short (part number 35601-31010-999). Both North American and E1 General Export models used this for the model J, with North American models changing during K production to part number 35601-31660-999 which had a stalk roughly an inch longer.
The rear turn signal stalks had the wire coming out the side of the stalk at about the mid point, and pretty much looked the same from 1972 through to 1976, first under part number 35000-31815-999 for the 1972 model year, and then under part number 35603-31010 depending on which parts book you refer to.
The J model rear signal light lenses were red, the front ones were orange, and the round, flat reflectors which were bolted to the outside of the turn signal housings in most markets each had six facets (looks like a six slice pizza). Where fitted, for E1 General Export versions, all four signal reflectors were orange. Other countries varied - please refer to the Country Specific Section for details.
The rear turn signal mounts on early J's are stalks which are welded to the tail section of the frame as seen to the right. These appear to have been removed at about frame 22007 and the rear turn
signals just bolted to the frame in most markets.
In North American E3 and E28 markets, the stalks were replaced by adapter plates (part 41640-33001 and 41650-31001) to preserve the same extension.
The horn was chromed and vented in appearance.
The head lamp bucket chrome surround was not round, but has a flat area on the lower edge.
The rear view mirror mounts were 8 mm thread (note that the mirror anti-vibration stand-off's did not appear till 1974) and the mirrors had the Suzuki 'S' stamped into the metal backing.
The instrument cluster used plastic housings and there were several versions of these.
The clear plastic lenses had a slight crown, and stood slightly proud to the casing they were mounted in
All the gauges had black faces.
Some gauges had raised indicators on the gauge face.
Both MPH and KPH indicated speedometer clocks were offered depending on the specific market.
The warning/indicator lights were from left to right on the tachometer: green for neutral (there is no LED gear indicator as was used in later models), red for high beam and orange for the flasher indication.
The under plates used in 1972 were unique to that year, having an offset large opening for the tachometer and speedometer drives specific to that model year.
Frame number plates varied by country, but typically was an aluminium plate having a black background, and riveted to the headstock. The frame number was stamped into the right side of the headstock.
The tank fuel cap was secured with a latch, and the radiator fill cap cover was metal - both are marked in the photo to the right. Note that the radiator label shown would actually have been attached to the top and not to the bottom of the cover. See this section in the Appendices for more detail.
The ignition key used a 5 digit code, and was one sided, unlike the double sided 3 digit coded keys introduced in 1974.
The seat pans are interchangeable between 1972 and 1973, and very nearly interchangeable for all years. There was no seat lock - a thumb latch was used - so early pans to be used on a later model need to be modified in the area of the seat lock. Later pans to be used on a 1972 or 1973 ideally need to be filled in where the seat lock cut out is located. The seat covers in 1972 and 1973 had a distinctive
diamond pattern as seen to the right, with a one piece polished stainless steel surround trim (with no seat lock gap) and 'Suzuki GT' was silk screened on the back.
The rear brake plate did not have the wear indicator casting by the rear brake arm, but rather was smooth.
The rear wheel was largely unchanged through the course of the GT750 production, but the final drive gear did change having 47 teeth as standard in 1972. As well the rear shocks varied model to model, and the original shocks in 1972 were the 'high hat' style.
Probably the most noticeable feature of the 'J' was the front drum brake. The front fender also has the two rubber cable retainer lugs mounted into the top of the fender on either side (rather than one on the 1973 models and forward), and the fork stays are 'U' shaped, and not tubular.
An additional point to note is that the triple tree and top bracket are not interchangeable with later models - the fork tubes are 1 cm wider than the 'K' and later models (22 cm rather than 21 cm ). As the aluminium top brackets are often cracked at the pinch bolts, you will need to take special care when trying to locate a replacement should you need one.
The front forks are 35mm in diameter (as are all the GT750 front forks) and the 1972 and 1973 models share the same fork tubes and both used rubber fork gaiters. The 1972 J model as well as at least some of the earlier 1973 K models used 12 or 13 pleat gaiters (depending on how you count them) shown to the right. At some point in 1973 they changed to be 8 pleat gaiters shown on the left side of the
photo, and which are still available from Suzuki. Oddly, there is only one part number shown in the Suzuki parts catalogues (51571-33030), so perhaps there were two different suppliers ?
Also note that the fork oil drain screw is centrally located on the outer side of each lower fork leg.
The front axle was shared with the 1973 K model having a hex headed collar that the left fork left clamped on. The fixed end of the axle end is in shown in the upper photo to the right, and the two types of removable nut used for the J and K models and also for the L and later models are shown in the lower photo to the right..
