Bike Cutting out!

[Gaston Skydrol]

Hi Folks, I’ve got to admit I’m stumped. Bike running absolutely perfect but at low rpm (2500rpm) the bike missed a beat like it dropped a spark and then a few mins later just stopped. All lights work but nothing on the starter button. Did all the usual stuff on the side of the road still nothing. Sat there cursing for a few mins a then starter cct worked again and went I home. Took the tank and fairings off checked all the connections and cleaned all the electrical plugs. Checking the starter cct was alive all the time. Found nothing. Today took it out for a long run same thing happened same rpm, just trickling down a narrow lane. Left it 5 mins did nothing and it all came alive again. Any ideas what would isolate the starter button? It’s not the starter relay, but that wouldn’t stop the bike. I fitted a wedge tail system last year so just wondering? All the connections are good and I can’t find and chaffed wires. Tried it the other way i.e. got the bike running and messed with all the connections and found nothing. It’s running/starting perfectly so it’s not fuel. Ticks over like a clock. It does not misfire before it stops, it just stops. Wiggled the ignition key while running could find anything.

 

[mikeyboy]

What model bike?

 

[Gaston Skydrol]

R 80 GS paralever 1994 vintage.

 

[sidkn33]

My 83 R80ST suddenly stopped starting but in my case, letting it cool down didn't help.
I was the ignition module (ICU) - just went from good to bad
Swapped with a known good spare and all sorted. I went around the houses trying to diagnose though.

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

Sep 2, 2026

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...

• sidkn33
• Replies: 12
• Forum: Airheads

 

[squibb34]

I always think of the HES first, but you say the engine dies & then won't crank until it cools down, if I have read it correctly?

That leads me to suggest you consider: -

Side stand switch - unplug & jumper the female connectors to eliminate this from the fault find.
ICU overheating - these had some sort of thermal paste between the ICU & the ali heat-sink, that deteriorates with age. Clean up & use computer quality TP.
Kill Switch - could be worn given age. You flip it numerous times when the bike conks out & eventually it clears.

Less likely culprits: -
Headstock wiring/ign switch
Bad coil
Starter/lead/relay

@mikeyboy may have other suggestions

 

[Gaston Skydrol]

I always think of the HES first, but you say the engine dies & then won't crank until it cools down, if I have read it correctly?

That leads me to suggest you consider: -

Side stand switch - unplug & jumper the female connectors to eliminate this from the fault find.
ICU overheating - these had some sort of thermal paste between the ICU & the ali heat-sink, that deteriorates with age. Clean up & use computer quality TP.
Kill Switch - could be worn given age. You flip it numerous times when the bike conks out & eventually it clears.

Less likely culprits: -
Headstock wiring/ign switch
Bad coil
Starter/lead/relay

@mikeyboy may have other suggestions

The time elapsed before restart both times was less then 4 or five mins so I’m not sure that heat is the issue TBH. Cleaned and checked the kill switch also troubleshooted the “other way” and tried to kill the bike when it’s running moving every switch, ignition key electrical connector. Might be a red herring, but all three times the engine was at roughly the same rpm, around 2500-3000 rpm. Theres no side stand switch.

 

[DrFarkoff]

Please confirm that the starter will not operate when the bike stops

but functions again after 5 or so minutes?

 

[Gaston Skydrol]

Please confirm that the starter will not operate when the bike stops

but functions again after 5 or so minutes?

Yep, it’s a new starter as well. Sooper dooper Hitachi. No click, nada! Ignition cct totally dead. It always dies at the same (ish) rpm. A nagging thought it’s where the ignition advances maybe?

 

[Stirlingmoz]

I know you said everything was checked and tight but heat apart, the symptoms are consistent with loose battery cables or could it be one of the battery terminals failing mechanically or just an old and failing battery?

This would account for no electrics at all.

The heat thing is puzzling though.

Any components that are fritzed, bean can, ignition module etc should fail in a crank, no start, state.

 

[DrFarkoff]

Yep, it’s a new starter as well. Sooper dooper Hitachi. No click, nada! Ignition cct totally dead. It always dies at the same (ish) rpm. A nagging thought it’s where the ignition advances maybe?

Okay so I am getting a vibe the voltages are zeroing

I do not know why people spend all the money on those

Anyway, my idea would be to take it out for a run and as soon as it experiences the cut out and the starter won't work, connect up a jump pack or a jumper battery and see if it works then??

 

[mikeyboy]

I think the first place I’d be looking is the connector from the rh switchgear to the main loom,maybe it’s been pulled loose or has corrosion.
Should be cable tied to the fairing bracket on the rh side.
It has the feed to both the kill switch and the starter button,and obviously the wires back to the starter relay and ignition.

 

[Gaston Skydrol]

I think the first place I’d be looking is the connector from the rh switchgear to the main loom,maybe it’s been pulled loose or has corrosion.
Should be cable tied to the fairing bracket on the rh side.
It has the feed to both the kill switch and the starter button,and obviously the wires back to the starter relay and ignition.

Done that, lost four men. Likewise when I had it running with the tank off fiddled with all the wires and connections. No corrosion on the pins and checked the wires at the back of all the connection plugs. Took r/h switches apart as far as possible and used a meter to confirm the connections.

 

[Gaston Skydrol]

Okay so I am getting a vibe the voltages are zeroing

I do not know why people spend all the money on those

Anyway, my idea would be to take it out for a run and as soon as it experiences the cut out and the starter won't work, connect up a jump pack or a jumper battery and see if it works then??

That was my next plan, remove the starter cover at home and set off with a pair of jumper leads. My Hitachi was on special offer or I wouldn’t have bothered, tbh I have had issues with the old starters but the they always got me home and lasted well. I have other bikes in the garage but the airhead is the only one I lose sleep over when it’s not working. I bought an XT 700 to save it in winter but still ride it most days. The other bikes just don’t scratch that itch.

 

[DrFarkoff]

That was my next plan, remove the starter cover at home and set off with a pair of jumper leads. My Hitachi was on special offer or I wouldn’t have bothered, tbh I have had issues with the old starters but the they always got me home and lasted well. I have other bikes in the garage but the airhead is the only one I lose sleep over when it’s not working. I bought an XT 700 to save it in winter but still ride it most days. The other bikes just don’t scratch that itch.

I think Wedgetail has a cut out below 10.5 volt to protect the system

The Starter is a bit of a mystery But a dead shorted battery could do that I have seen it before

Perhaps and easier thing to do is change your battery for something similar if you have one in the garage ????

Mikeyboy's post about the switchgear connection is a possibility but I cannot figure out Why it would come back after 5 mins without intervention?? Hence my Dead short Voltage / battery thought

 

[Gaston Skydrol]

I think Wedgetail has a cut out below 10.5 volt to protect the system

The Starter is a bit of a mystery But a dead shorted battery could do that I have seen it before

Perhaps and easier thing to do is change your battery for something similar if you have one in the garage ????

Mikeyboy's post about the switchgear connection is a possibility but I cannot figure out Why it would come back after 5 mins without intervention?? Hence my Dead short Voltage / battery thought

Battery is one year old and reads 12 v on the meter charging system working fine. Starter turns as fast as normal. When it’s dead the lights etc are a bright as usual. Surely if the battery was below 10.5 I’d notice?

 

[DrFarkoff]

Okay so my advice at this stage is

Go and strip it down So you can access all connections but keep it rideable

and when it does the stop reach in and wiggle connections

I am confused to the incoming information to be honest

So just eliminate one thing at a time and don;t just fire a parts cannon

 

[Gaston Skydrol]

Okay so my advice at this stage is

Go and strip it down So you can access all connections but keep it rideable

and when it does the stop reach in and wiggle connections

I am confused to the incoming information to be honest

So just eliminate one thing at a time and don;t just fire a parts cannon

I’m sure it’s something stupid. I had similar last year, it would cut out and I had nothing. Totally dead no neutral lights, like the battery was disconnected………Searched the loom and found a few bare wires near the ignition switch. The loom is in surprisingly good condition for the age/mileage. No corrosion on the connections and no bodge repairs. A far cry from the R 65 I have under maintenance. That poor thing has suffered big stylee. It’s gonna take a big commitment timewise to get it anywhere near the street. At least with the Roo Bar and fairing on the GS there’s plenty of space for the cables.