I was on a run with my wife on our lovely K100 when there was a shudder from the engine and then the ignition cut out leaving us stranded on the hard shoulder of the motorway.

Checked the plugs - indicating a bit rich (which I already knew) but all plugs sparked when earthed against cylinder head (not fat, blue spark though). All lights, indicators and horn working fine.

Started engine after cleaning plugs and it immediately fired up - hooray! But it wouldn't rev, only tickover. As soon as I touched the twist grip the engine cut out. I tried to crawl off the motorway at tickover revs - nope. When 1st gear engaged and load applied the engine cut out.

The whole time it was ticking over, the battery warning lamp was lit which seems to point towards alternator problems?. After half an hour tinkering I had to admit defeat and call a breakdown vehicle for tow home.

Got back and tested the Odyssey battery - not fully charged but not discharged either. Checked brushes on alternator - a little worn but within permitted tolerances. I removed the regulator and brushes as a starting point because the complete item is relatively inexpensive to replace. Damn cold in my shed so given up for time being. Thinking about coils, ignition pick-up, the 'black box' behind the steering head or (heaven forbid!) the ignition control unit.

Suggestions anyone?

Yes I have an idea.....

Check the throttle valve switch on the back of the fuel injector rail.
(just over your left foot)
This switch will cut the fuel injector when you release the throttle.
Just unplug it and try.
I heard of people finding it full of water.

Bert

Firstly I must compliment you on a really nice rebuild and am looking forward to the higher res photos minus the grey slime ??? I have to say I like the sound of Bert's fix as it might be nice and simple and we have to keep reminding ourselves of the KISS principle as it is so easy to go off on a tangent. Hopefully that is all your alternator light is as mine won't go out unless it has had a bit of a rev and in your case it would be catch 22. Having said that I had my alternator overhauled with one gold plated bearing costing $60 AUD but now the alternator light seems to indicate the battery is on its way out as it goes out as per usual and then glows faintly for quite some time and then goes out completely. By the way what is the secret to getting the plug off the throttle position switch and therefore fuel injectors?

Regards,

Phil Mars

The Throttle position switch is cutting the fuel injector when you decelerate.
This is to avoid to have back fire in our exhaust.
If this switch is bad, the engine will run only on the iddle circuit.

Bert

Thanks Bert and Phil for comments. I tried unplugging the throttle position switch as you suggested but no luck. Took it off to have a look and it seems to be in very good condition with a distinct 'click' when the throttle cable is moved about 1mm from stop.
Also fully charged battery, cleaned HT leads (again) and cleaned the brushes on the alternator but it won't even start now. Dropped a tool and it caught the mudguard on the way down putting a chip in new paintwork. Aaargh!
I'll check the timing tomorrow in case something has vibrated loose.
Col