GT750 Wire Harness Routing and Tie Points
Click on any image to see a larger version.
Over time, the wiring inevitably gets fiddled with, and the ties, connections and routing get changed. All of the GT750's used a similar wiring harness layout with just a few minor differences.
- The wiring on the underside of the engine was routed as per the photo below.Page 31 of the Suzuki GT750 shop manual also specifies the bolt numbers used for securing the clamps, which are: #8, #10 and #14 for the alternator and contact breaker leads
- The engine was grounded to the frame by a mesh strap (1) connected to crankcase bolt #22 (marked as item 2)
Clamps securing the alternator and contact breaker leads are held by #6 bolt.
The main wire harness runs up the left side of the frame, under the fuel tank and starting at the rear is secured as follows (reference the photo to the right, bottom to top):
- There are usually two small vinyl covered band clips securing the wires running to the turn signals - how the wire actually gets into the turn signal housing varies by year, and up till the 1977 B model there are no factory installed ground wires (the ground returns via the frame - not great, but it usually works).
- A larger clip on the left frame rail to hold the rear tail-lamp wiring, as well as the turn signal wiring.
The rear wiring is run under the rear frame brace and under the rear frame cross member by the oil tank, and then connects to the #2 wire harness which has the leads for the regulator, alternator, rectifier, battery connection and rear brake stop switch. This was originally part 36620-31001, and had several supersession numbers indicating minor changes
The mounting plate for the regulator, rectifier, indicator solenoid and termination/connections went through several iterations. The different versions of the clamp securing the wire harness connector blocks and mounted on the back of the panel is shown below.
Continuing along, the harness is tucked under the left upper frame rail and then to the inside of the left frame rail and secured by two clips shown in the top half of the photo to the right (marked as 1 and 2).
- The battery ground connection (originally a braided lead) is as shown in the lower part of the photo (item 3).
The brake stop switch wiring runs behind the air box and under the cross member below the battery ground connection point on the frame.
- The spark plug leads run inside the frame rails.
- Depending on whether a cooling fan is fitted or not, a relay will be mounted on the small plate (item 1) to the right of the frame back bone, and if no fan is fitted then this is empty and just used as a ground connection point (item 2).
- Again, if no fan is fitted the leads for the fan temperature sensor are tied up and secured to the frame back bone (4), and there is also one clip usually between this point, and the battery indicated as 3.
- Several versions of harness were used, and the principal problem is the connection marked as item 5 where the red, black with white stripe and orange wires connect. Early harnesses used bullet connectors (1972 through 1975) and then as can be seen this 1976 harness used a white nylon pinned connector - if you are going to mix and match harnesses, then you will need to have some additional connectors and a crimper available so you can match up the ends.
- The wiring harness then continues to the headstock and is secured at the headstock by a special rubber band (item 1 and part number 09462-00056) which is no longer available (as of this writing)
- J and K models do not have the LED gear change indication, but just a neutral lamp and so have only one main harness (36610-31001) running to the headlamp bucket.
- For the L and later models having the gear position indicator the main harness changed to part 36610-31200 and then through several supersession numbers for the M, A and B models, and a second harness (36660-31200) for the gear position indicator wiring was added (shown as item 2 in the photo to the right)
- The L and some early M model head lamp buckets used plastic clips and a metal plate (36682-31200) to mount all the termination blocks neatly in the headlamp bucket - lower left and centre are the 1974 and very early 1975 style, right is later style
Other models were not similarly equipped (and as a result, were much easier to work on !). The bucket itself was grounded to the frame via spacers through which the headlamp bucket mount bolts ran, part number 51821-31030.
- The model B (1977) introduced the use of ground leads for the turn signals.