I still own this GS1000S.
I remember that when I bought this bike, both the joy and the agony came at the same time.
Well then… at that time, I had no other way to commute, so I used this GS1000S for my daily commute. *In a way, it was luxurious~♪
It had a choke and all… the engine would start with the starter, which was better than the XJR1200… or so I thought.
By the way, the XJR1200 I owned before buying the GS1000S had a completely dead starter clutch, so I was bump-starting it every day to commute. (It had an FCR carburettor with a funnel.)
Youth is amazing… being broke is powerful~, I think to myself now as an old man.
But that GS1000S developed a strange illness.
Whenever it rained, it would always drop to two cylinders. Mysteriously, the same coil on one side would completely die. However, as time passed and things dried out, it would improve, and as long as it didn’t rain, the symptom would disappear entirely—a truly mysterious condition. *It’s Suzuki’s characteristic matte white coil found on their vintage bikes.
It bothered me so much that I installed parts from a GSX1100S Katana (which wasn’t available domestically at the time) and upgraded from points ignition to full transistorized ignition. But the problem persisted.
Even after checking all the harnesses, there were no major breaks—everything looked healthy.
Since the symptom only occurred when it rained and never otherwise, it wasn’t really a problem for riding the bike, but it was… quite? extremely unsettling.
Later, I thought maybe if I made an aluminum plate to go under the ignition coil and secured it with cable ties to keep water off the coil and surrounding harnesses and connectors, something might change. When I tried it, it worked like a charm! The symptom improved? or rather, stopped.
Since I’d replaced the coil with a new one during the transistorized conversion anyway, I didn’t think it was related. But at the time, I didn’t pursue it further and just went with “no symptoms, so it’s fine!”
However, after that, the bike entered a mysterious phase of blowing fuses (；∀；)
This is a wiring diagram excerpt from the GS1000S, but looking at it now, the grounding is really questionable, isn’t it?
Back then, the ground was taken from multiple points off the steel (frame)—a method you rarely see nowadays. Since it’s steel, corrosion builds up over time and the ground connection gradually deteriorates.
The main ground (the one running inside the harness) should really be taken from the aluminum (crankcase) for a safer approach, I think (^^♪
You can see why the trend of adding extra grounding (earthing) became popular with vintage bikes.
