Hello and thanks for all your comments and help . The bike is currently still around my mates house where I had to leave it , so I've not had any chance to take the reg/rec off or check the fuses.

Cammo - I have one question , in your very helpful reply it shows how you have fitted the 5 pin R/R off of an R6, but as mine has the engine is an older 750 ( FK I think ? ) so it has 2 sets of wires coming out of it with 7 pins in total , any idea if I can still use a newer 5 pin R/R ? and what 2 wires would no longer be needed ? . If not I'll have to try and get a replacement 7 pin R/R
Thanks
Mike .

I think you would be able to replace it with a 5-pin unit, but you'd need to check the 750 wiring diagram. I imagine the 2 extra wires are just positives or earths.

It doesn't sound like the original to me, I thought all 750 reg/recs were 5 pin units also.

Mike,
I spoke to Richard Palmer [vfr750 addict] and he said the 7 pin r/r is standard for the early 750.

He moved his to a place with more cold airstream, have a word with him, I will send you his email address.

Dave.

Hello Cammo / Dave ,
I've just taken it off of the bike and it is indeed a 5 pin/wire Reg/Rec . It's burnt a hole though the back of the unit , and left a horrible black sticky mess on the sub frame where is was bolted to.
I'll mail Richard and see if he can help , if not I'll look out for an R1 or R6 reg/rec . At least I will more choice with a 5 pin , as they seem more modern and popular.
Thank you both for your help.
Mike .

What happened to the main fuse?

magg wrote:What happened to the main fuse?

As I said before, the main fuse is to protect the wiring / stator from system overload of more than 360watts / 30 amps.

There is a chance that the fault in the reg/rec didnt draw 30 amps so the main fuse will be ok. A dead short will of course pull as much power as it can until something gives, which would be the main fuse.

If a main fuse with a rated current of 30A amp fuse is fitted , it should draw no more than 22A in normal use if the electrical circuit is designed correctly, however, it will not fuse [fusing current] until a load of between 40 and 60 Amps flows. [Depending on fuse spec type]
That's why rectifiers can burn out.

Arsey30, I agree with you statement regarding fuse ratings but would add that if the loom earth return leg was not connected at the front of the chassis, the main fuse should blow when a rect/reg fails.

IMO the inherent resistive losses in the loom earth wire would be one reason why the fuse does not blow. To overcome this issue it might be prudent to fit a lower rated main fuse to make sure that a rect/reg failure does blow the fuse.

I agree that the fuse rating should be low enough that no part of the circuit can draw enough current to melt or burn any part of it.

The best approach would to be fit higher rated items, e.g R/R and their connectors.

I know of an RC45 that caught fire when the r/r connector tags arced and burnt.

That could be an expensive fire. To make sure the rect/reg circuit is fused appropriately is one of the reasons I rewired my NC30. If the rect/reg fails, the added fuse will blow thereby protecting the loom and battery.