At first I didn’t think this was worth the time to post. My headlamp went out and this photo is what I found and replaced.
After the repair the surprise was the improvement in low end engine performance, easier start up, better and smoother idle and take offs. Not perfection, but very much improved. The high end performance was always there.
This is the headlamp and lamp socket off my 1985 GL1200 Standard. The bulb is still good, but retired – too oxidized. In the photo the front pin is the ground pin and failed. Even the burnt circuit was still complete to ground, but too scorched to pass current, so the head lamp didn’t work. The high beam indicator stayed illuminated even on low beam – it became the path to ground back through the high and low filaments. I had to cut away one inch of the ground wire as it got so hot the insulation melted to it and the copper was very hard and brittle.
The bike has 88,000 miles. The stator was changed at 68,000 and solder in. There are no electrical accessories added.
Performance history since 2001: It has always had some sputtering at startup, needs full choke to start in any weather (20 to 106 degrees). It seems to run on two cylinders in the first 15 seconds, then it feels like the others kick in and it climbs in RPMs quickly. After that I can back the choke down to 3/4s for few minutes and then get under way in the time it takes to put my helmet on. If I want to pull away smoothly I have to hold the choke at 3/4s. My choke has always pulled back to open on its own, so I have to hold it or put up with the roughness for the first half mile then it gets progressively better as it warms up in about three miles. After warm up it runs good at low RPMs.
When I first bought it I did spray out the carbs and it helped just enough to put off a bench cleaning. I have tried Seafoam and Mystery Marvel (a whole gallon over a few years) with very little improvement if any. Changing this burnt light socket has done more to improve the start up, idle, and first few miles of warm up that I thought I should share this experience. I would never have suspected an oxidizing head lamp pin could have such a detrimental effect. I wonder how long it was running hot and melting down. The few times I rode it with the headlamp out, it did not run any better, but only after it was replaced. In some ways I think I understand why, but then I really don’t know either. I have worked with avionics and electronics all my life and it never ceases to amaze what you learn with experience and where you least expect it.
I have read so many stories about a persistent ruff idle after cleaning and balancing the carburetors that I thought this might be something to check as a last resort. After all the headlamp is a big draw on current when it’s turning over slow and putting a burden on the ignition system’s power to fire strong. The lamp’s ground pin and the brass receptacle over the years corroded, over heated and burned up while somehow dragging down low end performance.
It's late and I almost want to go out and ride it instead of writing about it...