Wiring set up for Sports Racers Using a Cycle engine

[Jerry Poole]

Need some information on the use of a wiring harness. On a Sports Racer/Formula Car etc. using motor cycle engines, do you use the main wiring harness sourced from the motorcycle engine that you place in the car or do you fabricate your own wiring system for the Sports Racer? If fabricated, where do you source the components for a harness to be constructed? Appreciate any information or insight on this topic. Thanks, Jerry

[924RACR]

I modded the stock bike harness, stripping out the unnecessary stuff (lighting mainly) and adding resistors etc to replace unnecessary switches/sensors. Then there's a separate harness I've built up to support the needs of the car separate of the engine - sensors, rain light, kill switch etc.

There are some, I think George Dean among them, who can mod you up a harness from the stock bike harness.

Note that you'll either need to reflash the ECU to remove the 6th gear speed limiter, or run without the gear position sensor connected. Personally, I prefer to log what gear I'm in (as well as see it on the dash), so I just reflashed the ECU to remove the limiter.

[Marty Nygard]

It would have helped to know which engine you were looking at.
In general, a stock harness will need to be lengthened so it's a good idea to get rid of the lights, horn, etc at the same time. I once put a Honda 1000 into a street car and found that it HAD TO HAVE the stock ignition switch and rollover switch. The older Suzukies I used to use in the DSR were easer with fewer gotchas. If you are going to attempt this yourself, it would be almost mandatory to have the bike's manual and wiring diagram.
Or, contact George Dean Racing Engines. He has been doing harness modifications for as long as I can remember.
Good Luck.
M

[lowside67]

I went through this quite recently when I rewired my Stohr from start to finish. The way a factory Stohr is delivered, and what I duplicated in concept, is a two harness style - a "car harness" and an "engine harness".

The car harness starts at the battery and has connectors for:
1) Datalogger (Suzuki K-line, power, ground)
2) Switches (Ignition/Start, Fuel Pump, Brake/Rain Light)
3) Master Power Switch
4) Fuel pump

It also has these connectors for subharnesses:
5) Brake Light Subharness (pressure switch, rear light)
6) Starter Subharness (connects to stock Suzuki starter harness)
7) Regulator (connects to stock Suzuki regulator harness)
8) Engine Harness (connects to modified Suzuki factory engine harness)

For the engine harness, I had a stock modified by George Dean, although after the fact looking back I might have done it myself, it wouldn't have taken too long with the wiring diagram) and he basically provided a handful of bare leads which I then put a connector on and interfaces with #8 above.

In my opinion, this car harness/engine harness style makes sense as it would make it far easier to change motors or engine management in future. Reusing the factory engine harness makes this a much faster process and skips trying to track down all the factory connectors, etc to build it from scratch.

-Mark