Red Wire By-Pass Mod ( ST1100 ) *

[KoTAOW]

Submitted by Rob Parker, STOC #218

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Red Wire By-Pass Mod ( ST1100 )

All ST1100 owners should consider this easy mod. It will greatly enhance the reliability of your charging system. This already marginal connection deteriorates with age and will eventually fail, possibly doing greater damage in the process.

OEM connector to starter relay.


Doesn’t look too bad, but don’t be fooled.


The solid red wire has been over heating at the crimp. This puny 18 gauge wire supplies all the power to your
motorcycles electrical system.


Corrosion and burning at the crimp.










Separate the terminal from the connector and pull out of the loom for a couple of inches.


Trim off the terminal and burned wire.


Slip a piece of shrink tubing over the lead and attach new inline fuse to red wire.  I used crimp on terminals
and soldered them.


Heat shrink the tubing.


Apply dielectric grease to fuse terminals.


Retape the wire harness and connect ring terminal to fuse link as shown. If your machine does not have this fuse link,
attach this end directly to the positive battery


The new in-line fuse holder should also have a 30 amp fuse inserted after all the wires are attached.
Finished product.



Thank You again for your contribution Rob Parker, STOC #218

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Comments by Norm Keller, STOC #8030:
This modification misses much of the electrical weakness in the ST1100 power circuit. The Main fuse is a common failure point but the best means of addressing the issue is to install a 70 amp relay to switch power to the fuse box red wires rather than depending on the ignition switch circuit.

Check out the post: Ignition Relay Bypass Modification ( ST1100 )

The suggested modification in this thread addresses the weakness inherent in the aging Main fuse connector and so has some merit, especially as these bikes age but the modification misses the main problem area. Installing the ignition circuit by-pass removes the heavy load from the Main fuse and so deals effectively with most of the issue.

A quick confirmation of the need for this one is a simple voltage drop test from battery + to the fuse box....I've seen anywhere up to one volt+ on some bikes.

Another area is the headlight ground circuit, check Headlight Ground Circuit Modification ( ST1100 ) in another thread to which I posted.