74 850 left me stranded

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I once had a coil fail when it got hot, once I worked out it was the coil getting hot, I made my way home the 10 miles by running the 250 yrds the coil would spark for after a 20 minute cool and then free coasting until I met an uphill slope. As it failed in the Lickey Hills I was able to coast most of the way home.
 
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YING

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Maylar,
Please let us know when and if you find your problem.
Thanks,Mike
 

motorson

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I read through most of this, didn't see this recommendation for the coils. My Norton friends around here, and I, recommend taking the spade lugs off of the coils and replacing them with ring connectors and a nut.
 
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Fire it up & jiggle/play with all related wiring, might get lucky & easy stuff 1st.
 

Fast Eddie

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A friend of mine was touring Europe on his MK111 some years ago and suffered cutting out / poor running problem. He was in the Alps. Riding alone.

He couldn’t see any obvious faults, but jiggled things around and the problem seemed to go away, so he crossed his fingers it’d make it home and spent the remaining days of the ride listening carefully to the running of the engine and planning a thorough re wire.

But it never happened again, and the urge to re wire diminished, And several years later it still hasn’t been re wired and is still running fine !
 

Onder

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A thought about the coil-heat issue. I knew a radio guy who told me he used to trouble shoot radios (remember them?) by
hitting the capacitors with a compressed air can so as to freeze them. If they were dodgy he said they would work and as soon
as they warmed they would quit. Said he did it all the time. Perhaps a can of compressed air would be useful here. I know I use them to clean computers and they do work well as a refrigerant.
 
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Went for a ride yesterday with intentions of doing about 150 miles with a mate. Lovely clear day in the 70's. The Norton ran flawlessly... until it didn't. At about 30 miles it gave me a pop-pop-pop and wouldn't stay running. Coasted to the side of the road and had a look-see.

This is a superbly maintained 74 850 MKII. Amal carbs, TriSpark ignition, TriSpark coils.

I had fueled up before the ride. Pressing ticklers made no difference. Both cylinders were affected. Thank God for e-start, as I was able to just push the button during troubleshooting.

Took the points cover off and did the TriSpark self test. The LED came on but it flickered, it was not steady as it should be. I carry a spare TS ignition and it's a simple swap even at the roadside. No difference, including the self test indication.

I checked the coil wires by tugging on them and everything was tight. Resigned to failure, I called a tow vehicle (a $375 ride, ouch).

When I got the bike home it sat in my garage for a half hour while I had a beer and sulked. Eventually I put the key in it, tickled the carbs, and she fired right up like nothing was wrong. Warmed up and idled steadily. Great. How do you fix something that's not broken? I'm not sure how I'm going to proceed here.
Dave, I have loads of experience with EI ignition failures. That said, I have none regarding the TriSpark. The issue you describe is most common due to either an ignition coil or EI "black box" failure that is temperature related. In other words, once the defective unit heats up, it fails. Once it cools down, it will function until it heats up again. This was a common problem on early automotive EI systems.
 

maylar

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Dave, I have loads of experience with EI ignition failures. That said, I have none regarding the TriSpark. The issue you describe is most common due to either an ignition coil or EI "black box" failure that is temperature related. In other words, once the defective unit heats up, it fails. Once it cools down, it will function until it heats up again. This was a common problem on early automotive EI systems.
OK. But having replaced the EI on the roadside with a cool one would rule that out. And the TriSpark coils are extremely robust, so I think chances of one being intermittent are slim. Not impossible, of course, but unlikely.
 

maylar

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Troubleshooting Update

Recall from post #1 that my motor ran when I got the bike home. That was using my spare EI module. Yesterday I put the bike on my lift, took the tank off, and hooked up a remote fuel supply.

A consequence of ham fisted roadside troubleshooting is that I had stripped out the threads for one of the points cover pillars, so the first item on my list was to helicoil those 2 holes (2BA threads), and I reinstalled the original IE. Motor would not start after that. TriSpark self test would not pass. No spark at the plugs.

Coils check fine. 12 volts to the coils, 6 volts between them when I grounded the wire to the ignition. I created a "points simulator" by sparking that wire to ground (with a condenser) and both plugs sparked. I measured 12 volts at the kill switch fed IE power wire, but that's with no load. Bypassed the kill switch and the self test passed. Sparks from both plugs.

Turning the engine over however did not produce sparks. The LED on the TriSpark didn't flash. Rotor is tight and rotating. I put the spare IE back in, and the self test works and I get sparks with the engine cranking.

I now have fuel and spark but the engine will not fire. Not even a pop. Put a charger on the Shorai, and called it a day. To be continued today.
 

RoadScholar

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Talking of simple things… a blocked tank vent is not a possibility ?

This is my guess as well; you said the bike died shortly after refueling. A plugged vent can cut off fuel flow in as little as 10 minutes with a full tank, longer with less fuel.

Tri-Sparks (and Boyers) like 3 ohms of total primary coil resistance, they will function reasonable well with a range of 2.8 to 3.2. Below 2.8 asks the box to handle greater current flow (amps), above 3.2 and the box begins to lose it's ability to interest the coils in making a hot enough spark to do much more than knock a careless technician on his/her butt.

I suggest that, after you do the vent test that you measure the combine resistance across both coils, if it is beyond the range then measure each coil separately, you should see a range of 1.4 to 1.6, if you have a bad coil it won't hide from you. If you do detect a bad coil I figure that the "good" one has a packed bag and is getting ready to follow it's ailing mate. A twin tower 3 ohm coil is less expensive than 2 individual coils.

Best.
 

baz

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Went for a ride yesterday with intentions of doing about 150 miles with a mate. Lovely clear day in the 70's. The Norton ran flawlessly... until it didn't. At about 30 miles it gave me a pop-pop-pop and wouldn't stay running. Coasted to the side of the road and had a look-see.

This is a superbly maintained 74 850 MKII. Amal carbs, TriSpark ignition, TriSpark coils.

I had fueled up before the ride. Pressing ticklers made no difference. Both cylinders were affected. Thank God for e-start, as I was able to just push the button during troubleshooting.

Took the points cover off and did the TriSpark self test. The LED came on but it flickered, it was not steady as it should be. I carry a spare TS ignition and it's a simple swap even at the roadside. No difference, including the self test indication.

I checked the coil wires by tugging on them and everything was tight. Resigned to failure, I called a tow vehicle (a $375 ride, ouch).

When I got the bike home it sat in my garage for a half hour while I had a beer and sulked. Eventually I put the key in it, tickled the carbs, and she fired right up like nothing was wrong. Warmed up and idled steadily. Great. How do you fix something that's not broken? I'm not sure how I'm going to proceed here.
Remind me never to buy a trispark!!! :D
 
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