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Is my coil on the way out ?

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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 08 Apr 2022 at 18:47
If you can safely, next time, stop but don't turn off the ignition. Then pull a plug cap off, or remove a plug (ouch) and see if there is a spark when you spin the engine.

Brian.

Better 5 minutes late in this world than years early in the next.
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 08 Apr 2022 at 20:21
I am starting to suspect kill switch or ignition switch. Memory (but which is fallible and can also tell me fibs) says that the ignition switch has 3 outputs, one of which goes to the ignition circuit, via the kill switch. Note that this path does not involve the fuse box, but is a direct connection to the ignition coils. I now suspect dodgy contact(s) in the ignition switch, also the connectors are bullets plugged into the bottom, 4 of them, which could be loose or crudded up (guess how I know that can happen). This could explain why turning it off then back on fixes it, until the next time it decides not to work. Of course on the LM this is a tank off jobbie to get at the ignition switch. Bear in mind how old it will be, also your handlebar switches (and specifically, the kill switch) if they are still the originals. Also there are connectors in between.

Appendix: I know some people don't like to use the kill switch to avoid wearing it out, but also bear in mind that often these kinds of switches, as used in motor vehicles, have sliding contacts, so that they are self cleaning. So if left undisturbed, tarnishing and oxidation can build up to block the electrons. Use it or lose it! Big smile





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Simond Quote  Post ReplyReply Direct Link To This Post Posted: 08 Apr 2022 at 22:23
I’d certainly agree with Mike re using the kill switch regularly to clean the contacts, but that doesn’t explain it dropping onto one cylinder.  

I agree with Brian too, it’s not about getting warm, it’ll be well warmed up after 50 miles.

I’d suspect a dodgy connection somewhere.  Might be a tired spade connector or bullet socket, or a grotty ground.  

All these degrade with age, and might need new terminals crimping onto the wires, and any of them might shake,rattle and roll a bit as you’re riding, though it’s not obvious why it would take an hour or so to fail, nor why it should get better when you start again.


Edited by Simond - 08 Apr 2022 at 22:27
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ranton_rambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2022 at 07:42
My kill switch is soldered together, but I agree it’s worth looking at the ignition keyswitch. I had an intermittent issue on my Spada which turned out to be that.
It never caused any misfire problems but the charge light would randomly come on, although only when headlight on. It happened when I was following a car one day and I realised the light went off at the same time. There was some other clue as well, but studying the wiring diagram meant it could only be the ignition switch or something in the loom.
But this case seems to be different in that it only causes one cylinder to drop out if I remember right?
Ian 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2022 at 07:59
I have been watching this thread it points to something failing through vibration or heat 

Have you looked beyond the electrics? An inlet overheating? 

That was the reason the Guzzis with metal inlets had 2 fibre gaskets to the head just a random thought. 

But an easy check if the inlet is real hot. However the issue does appear electrical. I take it everything was fine prior to the Sachs ignition? So just maybe that has a faulty component it is not unheard of
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2022 at 09:32
Worth spraying electrical contact cleaner into every switch you can find, including the ignition. Then operate the switch several times.
Not only will ti=his clean the contacts, but it leaves an oily film which keeps the green gremlin away.
Worth spraying every connector too.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ranton_rambler Quote  Post ReplyReply Direct Link To This Post Posted: 09 Apr 2022 at 10:30
Yes, I agree.
When I did my top-end refurb I pulled every connector apart and cleaned the contacts, and also replaced hardened/cracked sleeving etc while everything was accessible. No electrical problems since.
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Ken-Guzzibear View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Ken-Guzzibear Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2022 at 07:20
That is tempting the fickle finger of fate mate ....
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Brian UK View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Brian UK Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2022 at 08:19
Most electrical problems are caused by poor connections. Components don't actually fail that often.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cowboy Quote  Post ReplyReply Direct Link To This Post Posted: 10 Apr 2022 at 08:59
I have a 73 MGB GT which are notorious for electrical gremlins and I do what Brian suggests. Every time I am working on it and see any wiring connections they get a spray of contact cleaner. Do the same with the Sport now too. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2022 at 22:22
This is a new angle on my problem for sure. Looks like tis back to basics. I may have to get a fresh can of electro-lube, It is good stuff alright
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Mike H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 11 Apr 2022 at 23:13
Originally posted by Simond Simond wrote:

I’d certainly agree with Mike re using the kill switch regularly to clean the contacts, but that doesn’t explain it dropping onto one cylinder. 


Should have explained more - I was thinking more in terms of a Voltage drop - suppose one ignition circuit was weak for some other reason, it might also be reasonable to suppose it's the first side to pack up working.

But the something heating up idea also has merit. Big smile


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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gianni Quote  Post ReplyReply Direct Link To This Post Posted: 12 Apr 2022 at 09:52
Originally posted by ranton_rambler ranton_rambler wrote:

but the charge light would randomly come on, although only when headlight on

That is probably the "second fuse down is loose" problem documented hereabouts.

The +ve feed to the headlight main/dip circuit also feeds the +ve side of the charging lifght and (usually) the front brake switch. When the fuse is loose and is stressed by one or more of the above functions it goes sulky. The feed to the charging light then works in reverse (so it lights up) and the headlight/brake lights stop working.

Look for the fuse with the red/black and red wires coming out and wiggle it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 14 Apr 2022 at 08:30
Originally posted by Brian UK Brian UK wrote:

If you can safely, next time, stop but don't turn off the ignition. Then pull a plug cap off, or remove a plug (ouch) and see if there is a spark when you spin the engine.


I am certainly going to try this next time it happens Brian. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote TheWrongTrousers Quote  Post ReplyReply Direct Link To This Post Posted: 30 May 2022 at 17:32
Well I did over 400 miles on this bike over the weekend down to Dartmoor and back. Had all of this advice in mind in case it played up. Now it refuses to go wrong at all. Perfect bike in every way. Whatever it was is in remission and long may it stay that way. But jeez the price of fuel !!!
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