R75/5 blowing fuses when starting

[gspd]

In over five decades of doing this I can't recall ever encountering a situation where a bad ground alone was blowing fuses.
Keep us posted on how things pan out.

[Rob Frankham]

In over five decades of doing this I can't recall ever encountering a situation where a bad ground alone was blowing fuses.
Keep us posted on how things pan out.

It#s vaguely possible but very unlikely and I'm very doubtful if it is possible in this situation.

FWIW, given a connection (Earth or anywhere else) where an intemittent break in a circuit involving inductive and/or capacitive loads is causing a repetitive interruption of a current, the net current can be higher than the current with a perfect circuit and can cause a fuse to blow... but not something I would expect to see here.

Rob

[melville]

When my son installed the motor he built in his Z28 Camaro and tried to start it, we saw smoke coming off a small ground strap that was part of the ignition system. In doing his mods he had lost the original ground path through a much larger ground strap. Once he had a 0 gauge ground connection, it fired right up.

I think, from OP's solution, that his bike was making an alternate ground path that had a fuse in it.

[gspd]

When my son installed the motor he built in his Z28 Camaro and tried to start it, we saw smoke coming off a small ground strap that was part of the ignition system. In doing his mods he had lost the original ground path through a much larger ground strap. Once he had a 0 gauge ground connection, it fired right up.

I recall a similar situation in the early '80's. It was a Saab (or maybe a Volvo). The speedometer cable was seizing up every few months and nobody could figure out why. Turns out that the original engine to frame ground strap was corroded away and the speedo cable had become the path of least resistance to ground for the complete engine and transmission assembly. Asides from the speedo cable repeatedly jamming up at regular intervals, the car ran perfectly. Never blew any fuses.

[r67boxer]

Thanks for your continued input but I can only report what I did and what the outcome was. Unlikely maybe but that is the only thing that made a difference.

K

[Rob Frankham]

When my son installed the motor he built in his Z28 Camaro and tried to start it, we saw smoke coming off a small ground strap that was part of the ignition system. In doing his mods he had lost the original ground path through a much larger ground strap. Once he had a 0 gauge ground connection, it fired right up.

I recall a similar situation in the early '80's. It was a Saab (or maybe a Volvo). The speedometer cable was seizing up every few months and nobody could figure out why. Turns out that the original engine to frame ground strap was corroded away and the speedo cable had become the path of least resistance to ground for the complete engine and transmission assembly. Asides from the speedo cable repeatedly jamming up at regular intervals, the car ran perfectly. Never blew any fuses.

Getting off thread now but the original Minis had a similar recurring fault. The main engine ground was located beside the engine almost invisible from above. It was a fairly common fault that the vehicle would be running normally at highway speeds... bearing in mind we're talking about an original Mini... When the time came to slow down, the accelerator would be stuck... caused a number of accidents. The usual point of failure was that the vehicle ground either hadn't been attached during maintenance or it had broken. As a result, the only ground connection to the engine was via the accelerator cable and with constant high(ish) current, this would overheat and cause the cable to stick.

Rob

[SteveD]

Thanks. Timing was correct and it failed to blow a fuse when the harness was bypassed and when plugs were removed. So, I decided to go back to a poor or bad ground. My good friend and fellow Canadian biker Brett suggested that I replace the ground from the battery to the transmission. After much searching I found one and installed same. Voila, it started without blowing a fuse. Coastal corrosion was likely the culprit. Thanks to all.

Kevin

If my memory survives well enough, Duane was a proponent of checking that battery neg cable for greenness and corrosion. Good find.

[r67boxer]

Well, after another month of riding with no issues it happened again. Frustration would be an understatement. This time I queried a good friend from Langely, British Columbia who operates a motorcycle repair shop specializing in BMWs. Like many contributors to this forum, he's forgotten more than most know. After apprising him of what's been done thus far he suggested that I also check out the starter button. It's relatively new so I wasn't expecting any frayed wires etc. so decided to clean the contacts with an electronics cleaner. That is, I used the fine tip to inject the cleaner between the button/switch and the housing. After blowing air through it under pressure, I reassembled it and tried starting the bike. It started immediately and with only the 10 amp fuse! More than a month later it still starts readily and doesn't blow fuses.

Kevin