Author Topic: Electrical gremlins in '78 LeMans  (Read 124 times)

Online Ralph Plant

  • Gosling
  • ***
  • Posts: 134
Electrical gremlins in '78 LeMans
« on: August 16, 2026, 03:53:51 PM »
Hello all
I'm having some issues which I believe to be electrical..not my strong suit at all! I have a Dyna 111 ignition and coils which I installed about 20 years ago and have never had a problem.. Now after I've been on the road a bit the engine will sputter a bit and then come back to life. It may do it once or it may repeat..not sure if its the system or is there an issue somewhere else.
I was told that it may be in the kill switch.
I don't really know where to start.
Anyone have a clue?
Ralph Plant
Tiverton, RI
'78 LeMans

Online PeteS

  • Gaggle Hero
  • *****
  • Posts: 3719
Re: Electrical gremlins in '78 LeMans
« Reply #1 on: August 16, 2026, 03:57:52 PM »
Start with the kill switch. Just spray it with some contact cleaner while moving it back and forth. Switch gear was not their strong suit back then.

Pete

Online Ralph Plant

  • Gosling
  • ***
  • Posts: 134
Re: Electrical gremlins in '78 LeMans
« Reply #2 on: August 16, 2026, 04:26:18 PM »
So I've been told..I'll give it a shot..
Many thanks!
Ralph Plant
Tiverton, RI
'78 LeMans

Online Antietam Classic Cycle

  • Gaggle Hero
  • *****
  • Posts: 15107
  • Happily stuck in the past.
    • Antietam Classic Cycle
  • Location: Rohrersville, Maryland
Re: Electrical gremlins in '78 LeMans
« Reply #3 on: August 16, 2026, 04:47:56 PM »
All of the power to the ignition runs through the kill switch, and with a Dyna ignition, that's a significant load. Wiring in a relay is a good idea.
Charlie

Offline guzzisteve

  • Gaggle Hero
  • *****
  • Posts: 12973
  • "Just Ride It"
Re: Electrical gremlins in '78 LeMans
« Reply #4 on: August 16, 2026, 05:10:24 PM »
Kill switch kills the coils, black & white wires I believe, usually.
"Pray through Carlo & your bike shall be healed"
Location: Planet Earth

Offline blackcat

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • Posts: 9177
  • Location: Floriduh
Re: Electrical gremlins in '78 LeMans
« Reply #5 on: August 16, 2026, 09:58:14 PM »
If this is the original wiring harness and you plan on keeping the bike, you might want to consider a new Greg Bender wiring harness and a set of relays he sells to addresses those switches. At which point I’d take the switches apart and clean up the contacts.  Realistically not a huge amount of money given that it is a LeMans.
1968 Norton Fastback
1976 Lemans
1981 CX-100
1993 1000S
1997 Daytona RS
2007 Red Norge

Offline fotoguzzi

  • Gaggle Hero
  • *****
  • *
  • *
  • *
  • *
  • Posts: 20019
  • vee git tooh soon oldt und too late wise -my Dad
Re: Electrical gremlins in '78 LeMans
« Reply #6 on: August 16, 2026, 10:25:02 PM »
If this is the original wiring harness and you plan on keeping the bike, you might want to consider a new Greg Bender wiring harness and a set of relays he sells to addresses those switches. At which point I’d take the switches apart and clean up the contacts.  Realistically not a huge amount of money given that it is a LeMans.
what he said…but when was the last time you checked valve clearance? Your symptom could also be tight valves.
MINNEAPOLIS, MN

Offline moto-uno

  • Gaggle Hero
  • *****
  • *
  • Posts: 1495
  • Location: Burnaby , B.C
Re: Electrical gremlins in '78 LeMans
« Reply #7 on: August 16, 2026, 10:35:51 PM »
 
  At least 35 years ago I simply threw out the original switches and wired in some from a Yamaha 650 Seca and they have been through
hell and back (250,000 kms) and continue to work flawlessly . Put the originals in a box (and pass on to some future owner)  :azn:

Online Dukedesmo

  • Gaggle Hero
  • *****
  • Posts: 682
  • Location: England
Re: Electrical gremlins in '78 LeMans
« Reply #8 on: Today at 07:59:15 AM »
Whilst the switchgear on my LM2 worked fine (it was very low mileage and had lived indoors all it's life), it looked and felt flimsy especially the indicator (turn signal) switch so, in the name of reliability and continuity I replaced it all with modern (Ducati to match my other bikes) switchgear.


Will keep the original stuff in case originality is important to the next owner.
Le Mans II
Ducati 916
Ducati M900

Online PeteS

  • Gaggle Hero
  • *****
  • Posts: 3719
Re: Electrical gremlins in '78 LeMans
« Reply #9 on: Today at 08:17:24 AM »
My ‘76 LeMans still sports the original switchgear. The kill switch did cause a bit a grief this Spring but a little contact cleaner made it right. As far as replacing everything it all depends how much you plan to ride it. Mine is no longer a daily driver so I will stick with it until it falls off.

Pete

 


NEW WILDGUZZI PRODUCT - Moto Guzzi Door Mat
Receive donation credit with door mat purchase!
Advertise Here