More info on the safety relay problem.

[herocomplex]

I've done some extensive trouble-shooting on this and am getting some REALLY weird results. I'm really starting to doubt my sanity and I would like others who might not be as crazy tell me what they think.

Problem: Headlight won't come on.

Test 1: The headlight works when bypassing the safety relay with 12v.
Conclusion: The headlight switch works and the RLU works.

Test 2: The safety relay works when supplying 12v.
Conclusion: The safety relay possibly works (should only need around 6v right?)

Test 3: All 3 white and yellow from the stator suppy 14-15 volts AC when engine is running. Stator is new. Battery is charging.
Conclusion: Stator is fine.

This is where things start getting a little weird.

When the engine is off and the key is off there is 6v DC from the Yellow stator wire (disconnected from harness) to ground (0v when connected). The ignition was originally 3-position and has been replaced with a 2-position so perhaps OFF is actually the PARK position. This would explain the voltage (assuming the headlight runs off battery in PARK). The safety relay doesn't kick in so maybe it is faulty as well and won't switch at 6v.

This is where things get REALLY weird.

I double checked my multimeter with an AC source and with a DC source. It reads perfectly! When the Yellow stator wire is disconnected from the harness and I measure voltage across stator side and ground I get both 6v DC (possibly because it's in PARK) but I ALSO get an ~8v AC reading ONE WAY! Remember, the engine is off. What the hell? I checked my meter again against 12v DC and 110v AC, perfect readings with correct polarity for DC.

Plus I completely uncovered the yellow wire from the safety relay harness down to the yellow stator wire connector and I can find NO diode. Perhaps it was removed at some point (unknown history)? Things just aren't adding up.

If the diode were missing, the safety relay wouldn't work properly, understood. If the ignition is truly in the PARK position, the safety relay might have been damaged by always being on. But the measurements are so strange, I seriously feel like I've been taking crazy pills.

For now I'm going to bypass the safety relay by jumping the headlight to 12v with a switch to cut off the headlight when starting. Has anyone had an experience like this? What the heck is going on? I might just find another safety relay (or bypass it, or build one from scratch) and put a diode in the yellow wire. It's just too weird.

[5twins]

On the '78, you can bypass the light portion of the safety relay by unplugging the single blue/black wire running to it. This should make your handlebar switch funtion normally and all the time, engine running or not.

That RLU can cause some weird problems when it goes bad. You might want to bypass it to eliminate it as a possible cause.

www.excess650.co.uk/tips%20&%20tricks.htm

[herocomplex]

Actually, the bike doesn't have a switch for the headlight. Nor does it have a fuse box for some reason. Only a single fuse. Thanks for the link. I think I'll bypass as much as possible. Keep it simple.

[5twins]

Standards had the single fuse on the side by that safety relay. Specials got that multi-fuse box on top of the battery. You should have an on-off light switch on the throttle side if the control is a '78 (who knows, it might have been swapped out for a newer one). Originally, it worked with the key on, motor off, but as soon as you started the bike, that safety relay turned the light on no matter what position the handlebar switch was in. Bypassing it was just too simple on my bike by just unplugging that one wire .....