Intermittent electrical fault - blowing ignition fuses

[Matt06]

Hi guys,

My z750 has started to occasionally blow the 10a ignition fuse. I have replaced it a handfull of times over the last few months and it will run for a few weeks at a time before blowing again. This isn't something that happens when riding and only when pressing the starter switch.

I have taken the starter switch apart and cleaned it up with contact cleaner and checked the wiring back for shorts and can't seem to find anything. The wiring looks good and I've checked around the bars for pinched cables.

It may be a silly question, but as it's only occasional and when starting, I'm tempted to just put a 15a in instead of a 10a, but i guess this would cook some wires?

I was also thinking replacing the starter solenoid?
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Current: MT-10, Bandit, Grom, GPZ500
Previous: YBR125, GSXR400, ZXR400, MT-03, NTV650, R6, z750, ZX6R, MT-09

[Nobby the Bastard]

The usual cause of blown fuses where no other fault presents is a bad earth.
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trevor saxe-coburg-gotha:"Remember this simple rule - scooters are for men who like to feel the breeze on their huge, flapping cunt lips."
Triumph Sprint ST 1050

[Islander]

Blown fuses are caused by too high a current (amperage) flowing through them. This means that part of the circuit is presenting too low a resistance - the lower the resistance, the higher the current flow for a given voltage.

Check for chafed or broken insulation on the wiring (chafed areas aren't always obvious and can be hidden by grease or dirt). If the wiring and switchgear are good, then it may be the relay or solenoid to blame. You'll need a wiring diagram to understand how the circuit works, and a multimeter to perform tests.

Don't be tempted to replace the fuse with a higher value one. Fix the problem instead. Fuses protect the wiring from overheating.

[moonzoomer]

My first point of call would be the battery connections followed by the main earth from Battery to chassis connection, they build them dry nowadays so a quick clean around all negative (earth) connections is a step in the right direction.

[WD Forte]

It's possible it's the solenoid.
I dont know the Z750 but many solenoids have a fairly low resistance on the actuator coil and take a fair bit of current in use, albeit breifly.
A CX solenoid for instance wil take about 4 amps when cranking

If the insulation on these windings starts to break down they could start to short internally to themselves thereby lowering the resistance and increasing the current.

Put a meter on it,
For instance, my spare has a static resistance of 3.1 ohms
it would only have to drop a few ohms to increase the current
significantly ie
12 / 3.1 = 3.87 A
12 / 2 = 6A
12/ 1.5 = 8A
12 / 1 = 12 A

The problem may well be something completely different of course
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bikers smell of wee