Sudden cut out ...1984 R80

[Old Man]

Well, there I was full of the joys, riding through the Dorset lanes yesterday (which was a pretty warm day) when without any notice the engine stopped. There's plenty of fuel getting to the plugs but absolutely no spark. I waited until the engine cooled down and tried again. Nothing. The engine turns over fine but not a single firing on either pot. I've followed my Haynes manual to the letter and narrowed it down to the Control Unit. My question is this. When the Control Unit fails does it usually fail suddenly like this appears to have done?
Any help from you experts will be very welcome
Thanks
John

 

[bumpmuncher]

have you had the front cover off the engine lately

 

[degsey]

check the voltage of the battery

 

[Steptoe]

Could be the Bean can trigger unit or the ignition control unit.
Don't forget to also check the coil.

 

[Old Man]

It's clean as a whistle behind the front cover and there's little or no corrosion anywhere .... the bike's only done 23k miles in 29 years and most of that seems to have been dry riding.
Battery voltage is 12.5.
The feed to the Control Unit is good but I'm not getting any feed from the centre pin of the 3 pin terminal which links bean can to Control Unit under the front cover. This is why I think that the CU is duff. I haven't done anything with the coils except to check the contacts which are fine
Thanks for the help so far.
John

 

[bumpmuncher]

when replacing the front cover it is possible to displace and then trap the ign trigger and charge light wires and either sever them or partially sever them to fail suddenly at a later point in the near future

 

[ken brooks]

The control unit on my bike expired years ago, in just the manner you described. Running along fine at one moment and then..... dead! just as if the key had been turned off

 

[bwprice100]

Hi John

Pull out a plug, connect it to the HT lead and ground it. Turn the ignition on and then turn the kill switch on and off, if you get a spark at the plug then the coils are ok and it is likely the trigger unit or the amplifier module under the tank.
The amplifier module can fail if the heatsink grease dries up.
You can start by checking the input and output voltages for the amplifier module if the coil system is ok.

I hope this helps Brian

 

[Old Man]

Thanks to you all for the advice. I've managed to borrow another control unit, as well as a new Hall's sender so I can fix by elimination. Not at all sure what the jollop is to put in the join between control unit and heat sink but I haven't done the search yet. At a guess my Auntie Betty's chutney would be about right.
Cheers and thanks
John

 

[bwprice100]

Maplins sell small tubes of white heatsink grease, nice on toast.

 

[Old Man]

Maplins sell small tubes of white heatsink grease, nice on toast.

Excellent .. thanks

 

[Old Man]

Steptoe was spot on. The coil caused the fault. I was a bit surprised that it just stopped the engine dead without warning but I've learnt. Thanks for all your inputs.
Cheers
John

 

[piebaps]

Steptoe was spot on.

Isn't he always?