K100 Fuel Tank Electrical Connector

The electrical connection to the fuel tank provides power to the fuel pump as well as providing electrical signals to the fuel gauge.

Over many years and countless insertion cycles the plug on the wiring harness will wear itself to the point where it will disconnect from the socket on the tank from vibration or shocks in normal riding. Sometimes the plug will fall out while the bike is sitting. Can be frustrating especially if you've parked someplace you shouldn't have.

My last '85 K100 had a worn fuel tank electrical plug. And sure enough it fell out on its own. Interestingly it primarily fell out when the bike was parked. Maybe due to heating and cooling? I never found out. I tried tape which worked but had to be removed whenever the tank had to come off. The tape sometimes failed from heat or water exposure.

Finally when I'd gotten to the point where the plug would not stay in the socket I started looking around for replacements. I could not find the plug anywhere and there did not appear to be any easy way to replace the socket on the tank.

By chance I happened on the wiring for an old K100 alarm system. Turns out the OEM alarm kit uses the same exact plug as the fuel tank. The wire color coding of the two plugs is different but since the plug is keyed I simply noted which colors were at the same position on each plug. I cut the plug off the alarm harness and the old fuel tank plug off the bike harness. Stripped, soldered, and shrink tube sealed the new connection.
Worked like a charm. Never had another failure due to the fuel plug falling out of the fuel tank socket. Problem solved.

Someone must have posted this information before but just in case....

Tank connector

I know your pain.
These four pin tank connectors fail on a regular basis.
A simpler fix...Go to your local auto parts store, buy Ta flat four trailer electrical pigtail connector. Cut the old four pin off the bike and the tank and wire in the flat four trailer connector, works like a charm, done it to three K75's no more fuel pump problems.

CNRed said:

I know your pain.
These four pin tank connectors fail on a regular basis.
A simpler fix...Go to your local auto parts store, buy Ta flat four trailer electrical pigtail connector. Cut the old four pin off the bike and the tank and wire in the flat four trailer connector, works like a charm, done it to three K75's no more fuel pump problems.

Click to expand...

I'm confused - I'll have to go look at the tank again but my recollection was that the tank connector (tank is male, plug on harness is female???) was permanently fixed to the tank on the '85 (and presumably on the 83, 84, and 85 as well). Sounds like either my brain is wrong or something changed by the time they were making your K75(s).

Someone else know off hand?

-Gary

My '85 K100RS still has the original plug to the fuel tank. It is the kind that uses "diodes" instead of a float for fuel level indication (just low fuel lights). Years ago I fixed the same problem you are having by using a dental pick to close the gap of the female socket connections in the plug of the frame end connector. This makes the plug fit the male pins of the tank connector more tightly and haven't had any problems since. Just be careful not to close the sockets too much. Insert the sharp end of the pick beside the female socket using the plastic plug for leverage. It doesn't take a lot of force and you can watch the gap in the socket close. I hope my description makes sense to you.

Frank