1983 R80ST won't start - seemingly out of the blue

[sidkn33]

Hello all,

I have an R80ST that has suddenly and dramatically refused to start.
It was starting and running 100% fine, in fact it was better than fine - having been tuned using a Grok Harmonizer about 3 weeks ago - it just took me on a 1000 mile trip with no issues.Occasionally
I got a vibe that the battery is starting to weaken, but otherwise - all good.
I happened to have had the battery on an overnight charge last night and it was fully charged when I set off this evening.
I went into my local shop, came out 15 minutes later and with repeated attempts there was no sign of a spark - it didn't stumble or try to start -- the starter motor/engine is turning over.
Fuel is getting to the carbs = float bowls have fuel present.
After probably 10 attempts, the battery started to lose charge enought to turn the starter motor
I'm not too good on electrical issues - but my HT leads are newish and are fitted correctly at both ends, on both sides.
I used my car battery (car not running) with jump leads and was able to try again, but no joy - indicating it's not a battery issue?
The ignition module was quite hot to the touch, with bike engine being stopped for at least 30 mins and after attempting to start - is this normal?
I have a second bike - 1987 R100RS that I can use for emergency electrical parts - what should I try swapping over first?
Thanks in advance

 

[ChasF]

Sounds like a dead bean can (Hall effect trigger) to me.

 

[Adrian]

I would buy a new ignition module as they are fairly inexpensive. When they start are wearing out they cause various problems such as not starting or running badly. If it's not that keep as a spare for long trips. Hope it gets sorted soon.

 

[kirby morgan]

Take the spark plugs out and see if they are wet with fuel if not then it's a fuel problem.
Next reattach the plug in the ht caps, get a good earth and press the starter button. You should get a spark from the electrode both sides. Careful you don't do it near the exposed plug orifice.
If it's sparking then ignition is okay.
Battery, could be shot, are the jump leads heavy duty, as light crappy ones won't do it even with a car jump start.
These checks don't take long and may eliminate or confirm part of the problem.
Don't buy anything until basic checks are carried out.
My tuppence worth. Hope it helps.

 

[Gelandestrasse]

Check that you didn't operate the kill switch...

 

[sidkn33]

I've had a spark plug out of cylinder head, grounded to the head and connected to ignition, switching the kill switch on and off does sometimes create a weak looking spark but not every time I rock the switch.
Battery is very weak.
Why though with car battery jumped to the bike would I still get very weak cranking of the engine? Would a totally farkled battery mean that even with jump leads the engine will not healthily turn over?
Unfortunately the bike is stuck in a Tesco car park 5 milesfrom home so I am taking bits in the car to attempt fixing.
Jump leads are heavy duty.

 

[sidkn33]

Solved - it was the ICU.
I swapped the ICU with one from my RS and the ST started up immediately - helped by an emergency starter battery pack thingy which I forgot I owned!
Thanks for your assistance, all.

 

[sidkn33]

I would buy a new ignition module as they are fairly inexpensive. When they start are wearing out they cause various problems such as not starting or running badly. If it's not that keep as a spare for long trips. Hope it gets sorted soon.

That's what it was - many thanks

 

[timeandtide]

Other thing worth keeping in tool compartment (& not too expensive - especially if you get a secondhand one from MOTORWORKS) is starter relay.

 

[sidkn33]

I'm counting my blessings that this happened after a 1k mile round trip to Bordeaux and only 3 miles from home - I ride with a decent set of emergency parts, but nothing electrical, just cables etc
Lesson learned.
That said, this is the first time with 4 Airheads under my belt and probably 20-25k miles that I've had one just electrically stop - I don't want to cart my garage about with me, just-in-case.

 

[DrFarkoff]

You may find that your heatsink paste on the back of the ICU was actually hard and ineffective hence the overheating

 

[sidkn33]

Does anyone have a

You may find that your heatsink paste on the back of the ICU was actually hard and ineffective hence the overheating

Ordered some paste to go with the new ICU

 

[ChasF]

You may find that your heatsink paste on the back of the ICU was actually hard and ineffective hence the overheating

I had an ICU go faulty about 200miles from home which caused the bike to misfire and occasionally cut out. When I swapped it out for my spare I thought it had failed from overheating as the heatsink paste had dried out and was probably blocking the heat transfer rather than helping it.