SOHC.co.uk Forums > CB750

Main fuse blown

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Andy1976:
Help I'm in the s*!t big time. I've been checking my bike over prior to this weekends trip away. Everything seemed fine until electrics went dead. I checked the main fuse, fine,connector blocks etc, fine, it turned out to be loose earth wire on the battery.
The trouble I'm having now is that when the bike starts and the rev's hit 2000+ rpms, it's blowing the main fuse, it doesn't do it when on tickover.
I don't know what to look for and I'm supposed to be going away tomorrow morning.  >:( >:( 
The bike ran fine until now. 

Thanks
Andy 

SteveD CB500K0:
Sounds like a voltage regulator problem. These SOHC4 charging systems are pretty simple.

A voltage sensor in the regulator switches the field coil current on and off to regulate the amount of power produced by the alternator. If this is stuck (physically - it is a mechanical device) "on" then as the revs rise the power produced by the alternator will rise unchecked and blow the fuse (that's what it is there for)

If you have a spare or can beg, borrow or steal one, swap it out.

If not, you'll have to buy a new one or dismantle the old one and clean it all out.

No way you can tour on a bike with a knackered reg.

Sorry  :(



Bryan?

Andy1976:
Hya Steve,
I managed to get the bike to the local mechanic on friday morning, it turned out to be a wire shorting out on the ignititon barrel. Managed to sort it and get away for the weekend

SteveD CB500K0:
Weird that it only happened at 2k+ revs though.

Had me fooled though!

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