Ignition cuts out shortly after getting under way

Speaking of kill switch, I had a very similar problem last year - except the bike would NOT restart until it sat for over an hour. After several months, the problem was traced (thanks, Ken the Mechanic!) to the spring that keeps the contacts on the kill switch from touching. A little heat or vibration would cause the spring to settle on the contacts, killing the bike. Once the bike was completely cold, the spring would go back into place. FYI: this was a two year old component.
 
johnm said:
Sounds exactly like the famous Boyer ignition cut off.

Check the wires down near the trigger on the end of the camshaft. The wire breaks inside the plastic sheath. Check very carefully giving them a good pull. It can be hard to spot.

Very commonly the bike will cut out after a few km and will start again after 30 mins or so when it has cooled down and the wire contact is restored.
Click to expand...
After you're convinced all your hot wire connections are including kill switch are sound, check this.
Like posted, these connections break and are hard to spot.
They could have been compromised during the handling of the resto.
 
o0norton0o said:
^^^^^^ this is the method to live by,...... however, once you've tested all the things that can be tested you should understand that intermittent problems can defy testing since they may only break down under actual running situations.

Things like ignition switches actually can corrode inside and cause the contacts to be weak so they heat up and break down once they get too hot. I have drilled the rivets out of a sealed ignition switch to freshen it up and remove corrosion then rivet it back together when my key switch got old and crusty.

another possible cause is some sort of ground fault contact inside the headlight shell. Usually there's a lot of connections made inside the shell. If they ground against each other or the shell, it can act like a kill switch. I've had that happen too and some strategically placed electrical tape and shrink tubing can usually eliminate those issues...

Another cause is the handlebar clusters pinching a wire in the control harness against the metal handlebar. Also a corroded kill switch on the clusters is a common cause.....

Electrical issues take patience and a methodical approach... I like to replace the battery with my tester leads on the continuity setting where it makes an annoying tone, then go around wiggling the harness and components to see if you can find the poorly conducting component or the ground fault.

You'll find the issue, just be methodical...
Click to expand...
I totally concur that these electrical problems require the utmost patient methodical approach to troubleshooting. My current hypothesis is that this is something heat related, and/or voltage related over time. No amount of giggling wires seems to induce nor rectify the problem. I think I read something years ago that said if there is a grounding problem with the BB ignition that voltage can build up in the unit which will cause it to quit until said voltage dissipates?
 
Semitone said:
I totally concur that these electrical problems require the utmost patient methodical approach to troubleshooting. My current hypothesis is that this is something heat related, and/or voltage related over time. No amount of giggling wires seems to induce nor rectify the problem. I think I read something years ago that said if there is a grounding problem with the BB ignition that voltage can build up in the unit which will cause it to quit until said voltage dissipates?
Click to expand...
There are several possible reasons this can happen but the easiest way to rule out the issue is start with the Boyer first . It has already been mentioned ......

Run a ground wire from the battery to the boyer . Run a power wire from the battery to the boyer .That eliminates ALL the other wiring . If the bike runs fine , remove the ground wire ...... if it doesn't , you know where your problem lies . I have in the past had boyer issues much like yours .. Trouble shooting on the side of the highway is no fun . My tool kit includes a made up power wire . Hook it up to the battery and the other end plugs into the ignition which in my case is a trispark . All comes from roadside experience :(
 
nortonmargie said:
Speaking of kill switch, I had a very similar problem last year - except the bike would NOT restart until it sat for over an hour. After several months, the problem was traced (thanks, Ken the Mechanic!) to the spring that keeps the contacts on the kill switch from touching. A little heat or vibration would cause the spring to settle on the contacts, killing the bike. Once the bike was completely cold, the spring would go back into place. FYI: this was a two year old component.
Click to expand...
My “kill switch” event went like this :
left home at 5 A.M. to meet buddies for 80 mile leg to Channel tunnel train , heading to Normandy D Day beach trip. Arrived , started bike and left train in torrential downpour…got 400 yards and bike stopped on up ramp….feck….assumed ignition issue by bike behaviour, as in suddenly stopped firing .
Checked plug via kick and switching ignition ( Pazon unit) ..no spark 😖. Out with multi meter and testing started . broke the system down by splitting connections…checked supply to kill switch = ✅
Then checked continuity thru kill switch = 👎. Applied link wire to connector and away I went. Absolutely random event .
 
My "kill switch" event went like this: my buddy and I were in Deadwood with our Commandos in '74. Went to a car wash and proceeded to head to the Saloon No. 10 for refreshments. Went back to the bikes and my four month old bike wouldn't start. So for two or so hours we're going though everything we can think of, calling dealers on PAY PHONES for ideas until someone mentions "the kill switch". It was green. Real green. Lesson learned. Still have the bike.
 
I was in Deadwood on my BMW K1300s
Never technical issues but not the exhilaration of the Commando ... unless hitting redline in 3rd gear!
Dennis
Vancouver
 
" I did a full restoration on this bike "

SO , you took all the switches apart , removed dust , oxidation , and realigned contacts . 🫡

I think , if you carry a ' hot wire ' , and put it on , if it fires straight up , youll know its something .

SO , either a intermitent disconnect , a failure under heat . Condensors or coils . ( Boiling Coils - 6V . ARRGHH . Trash . Ditchem . ) or a intermitant earth .

Ignition cuts out shortly after getting under way


Thesell GETYA . If we knew then , wot we knownow .

ANY COIL over TEN years old , is SUSPECT .
On a good battery , a induced spark should be BLUE & WHITE and 1/2 inch jump.

red n yellow n 3/8 your DOOMED . Carrying a loose spark plug ( and gloves ) pulling a plug lead , running , and CHECKING THAT , will tell you somint , maybe .
Specially if its DARK . A cross head screwdriver which fits the inner steell bit in the cap , is as good . or a 6 inch steel rod . Thisll tell you the colour and the output .

Feeble spark in operating conditions tells you something is feeble .

M

Post in thread 'John's 72 Commando woes'

Sounds like dodgy coils .

Theres a CYCLE Magazine link here somewhere " Great Coil test " showing how useles Lucas coils are . After a decade a Lucas Car Coil is usually trash .
The SPORTS Coil was better . A 1/2 in plus rathern 3/8 weak spark .
:(

John's 72 Commando woes
John's 72 Commando woes
John's 72 Commando woes
John's 72 Commando woes



The Ring Ding 350 ( they pretended it was ' Race Developed " but we know better ! )...
 
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I had similar problem. Drove to mot station and it just stopped on its own without warning. After mot, 1 hour, started OK and almost got home. Stopped again ! Started OK after getting it back. Turned out to be a faulty coil which cut out after warming up. 1 coil goes, no sparks ! As earlier post found faulty one through resistance check. Between 3 to 4 ohms? From dull memory was required. Took a while to find. Boyer fitted at time. Roy
 
During the restoration, I had the light switch/horn cluster apart because I was getting intermittencies. The turn signal/kill cluster worked fine so I didn’t open it up. Going to do this for sure. I also didn’t know that one coil failing will take both out. I did not replace coils. I’m not sure how old they are, but they tested 2.9 and 3.2 ohms if memory serves (which it does less and less these days).
Ok guys, I’ve got a lot of good troubleshooting ammo! Will have at it this weekend and let you know what I find!
 
The yaki said:
I had similar problem. Drove to mot station and it just stopped on its own without warning. After mot, 1 hour, started OK and almost got home. Stopped again ! Started OK after getting it back. Turned out to be a faulty coil which cut out after warming up. 1 coil goes, no sparks ! As earlier post found faulty one through resistance check. Between 3 to 4 ohms? From dull memory was required. Took a while to find. Boyer fitted at time. Roy
Click to expand...
This is a common problem with BMW R 60/2
 
Ok, today I connected the BB ignition supply and ground direct to the battery. Started the bike and rode it up and down the road. It died after about 2 minutes. Then I took apart the kill switch cluster put my voltage meter on it and tested switch. No intermittencies. I started bike again and this time it died before I could get it first gear. I then disconnected the coils and tested resistance. 5.6 and 5.9 respectively. Reconnected and kicked it over. It died almost immediately, and this time it was permanent. Could not start it again. I know the coils are good because when you disconnect power from BB, it will discharge a spark, as these units do. I pulled plugs and observed a spark on both when turning on, then off ignition key. So issue is that spark is not being provided when it should be. Seeing that the bike ran for shorter and shorter duration each time the problem happened, I can’t think it could be anything else but a failing (now failed) BB ignition. Does anyone concur? Other thoughts?

Forgot to mention I swapped out battery with one from my Guzzi that has been working fine.
 
Mart UK said:
When you get to the no longer starts point, is fuel definitely getting to the carbs?
Click to expand...
Mart UK said:
When you get to the no longer starts point, is fuel definitely getting to the carbs?
Click to expand...
I know it sounds like slow fuel starvation, but fuel flows freely when depressing ticklers, plus when there is a fuel restriction problem, like forgetting to open petcock, the motor will bog and sputter a bit before quitting. It does not do this. It just shuts down immediately.
 
Mart UK said:
When you get to the no longer starts point, is fuel definitely getting to the carbs?
kommando said:
Those coil resistances are too high, they may produce a spark in the open air but do they when inside an engine with compression.
Click to expand...
You know when I put my meter on them, I was kind of expecting something around 2-3 ohms, but since they both tested similarly, i second guessed myself. I did not remove coils from the mounting brackets when I tested them. I’m thinking this could be the cause of these high readings?
Click to expand...
 
No, a 6V Lucas coil should test as 1.9ohm primary resistance, mounted or unmounted. The mounting brackets being over tightened or just from time will create earth leakages from the coils as the internal coils touch the outer metal cover. So also test from the connections to the outer cover, there should be infinite resistance, even a high resistance is a leakage.
 
Resistance seems a lot higher than I remember. I have a Boyer Mk4? from my mk3 working perfectly when removed for pazon unit. Free if you pay postage. Roy.
 
kommando said:
No, a 6V Lucas coil should test as 1.9ohm primary resistance, mounted or unmounted. The mounting brackets being over tightened or just from time will create earth leakages from the coils as the internal coils touch the outer metal cover. So also test from the connections to the outer cover, there should be infinite resistance, even a high resistance is a leakage.
Click to expand...
So, somehow, my Fluke 87, which I clearly don’t know how to use properly showed avout 6 ohms when connecting probe clips together. I pushed the Rel button and it zero-ed out. Tested coils again and read 2 and 2.2 ohms respectively. I’m now swapping out BB with another mk3 I had in my random bits bin. Don’t remember what the story is with it, but we’ll see.
 

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