Power disappears when I hit the start button

[ksquared]

The battery is charged and the bike runs great. But, now when I hit the start button, the electric power dies (i.e. the headlight and all other electrical devices are dead). It's as if the battery was disconnected. I heard a little click like sound in the area of the tank when I hit the button. I've checked the connector stack (pic below) and all seems well althought the top (red) connector was a bit dirty. The fuses all check ok. If I vigorously shake the bike forward and backward, the power comes back but it dies again if I try to start. Weird. Is there a relay under the tank? I guess I'm going to have to remove the tank and troubleshoot. Is pulling the tank a major job? Don't tell me I have to disconnect each of the 6 carbs!

electrics1.jpg

[ksquared]

Never mind. It's fixed. It was a loose battery negative connection. So simple I'm kinda embarrassed that I asked here before even checking it. Damn I like this bike!

[Larry Zimmer]

You're not the only one that's been to that rodeo!! Welcome aboard. Happy to have you along for the ride.

[herdygerdy]

While you've got the bonnet up, it would be worth checking the terminals in the red connector block that comes from the alternator for buildup of corrosion.
In your pic it is the one to the right of the green two wire connector (neutral & oil pressure switch connector IIRC). Those 1/4" spade terminals inside both the female connector (the red one on the alternator side) and the mating white one (in your pic) that goes to the regulator/rectifier can build up corrosion inside the plastic housing and melt the connector, resulting in a spontaneous 'fail to proceed' event. If they are good, a light spray of anti-corrosion stuff will put your mind at rest.
I came across one bike where the connectors looked fine from the outside, but once opened up, revealed really bad corrosion with melted internals. I believe this situation puts a lot of stress on the charging circuit and alternator.

[Larry Zimmer]

Excellent point/suggestion. Doesn't take much!! Try to run 5 amps through those connections with a 1/2 ohm resistance and you're loosing 2.5 volts. AND, your putting 12 watts heat in there. Might not sound like much. however, it will make for a bit of bother. And, after cleaning things GOOD, stuff the joints full of silicon grease.

[ksquared]

Good points Herdy & Larry. I pulled all 9 connectors for inspection and cleaned with Caig Deoxit D5. Should have done it some time ago. In my day job, I'm an engineer who works on Tesla stuff (electronics) so I know well the bad effect of a little resistance. Years ago I bought a Lotus Europa from a dealer in England. I had them add really bright driving lights. Well they were never really bright so I poked around and found a 4 volt loss at the lamps due to 16ga wire and a cheap rocker switch.