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#508682 10/02/13 10:17 am
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My previously ultra reliable [well since complete restoration 4 years ago, anyway] 1974, Interstate stranded me a few weeks ago with complete loss of power. It was towed home and, after evaluation, I found that the TriSpark module was faulty. I contacted Colorado Norton works who very kindly agreed to switch the module for no charge even though it was three and a half years old. Since installing the new module, [statically and dynamically timing it] I'm having a puzzling problem. It is severely misfiring on the left cylinder.
The bike starts easily with both cylinders firing smoothly [for the most part] in idle. As I slowly twist the throttle just off idle, the left cylinder cuts out. If I increase throttle it starts to fire again though with lots of popping and banging in the exhaust. At full throttle both cylinders fire but with intermittent misfiring. Suspecting carb problems (I have twin AMAL Concentrics, new with the rebuild) I took them both apart and cleaned them in an ultrasonic cleaner, even though they looked pristine. I have also done the following:
1. Measured the needle jets with gauge - perfect
2. Cleaned out the idle passageways with a #78 drill - twice
3. Checked both float bowl heights
4. Both slides move up and down synchronously and smoothly
5. Both choke slides are up and out of the way – i.e. not sticking
6. Swapped the high tension leads left to right - no difference
7. Changed both hypertension leads - no difference
8. Changed spark plugs probably 10 times
9. Added new bullet connectors to the black/yellow and black/white wires in the timing cover. These are heavier gauge marine wires, by the way.
10. I removed and disconnected the ignition switch and checked all connectors and cleaned them.
11. I pulled the handlebar module containing the kill switch apart and cleaned all contacts
12. Checked compression in both cylinders, and show 150 on the right and 147 on the left

I plan to have a jump lead from the battery directly to the Trispark module. However, I do not understand why only one cylinder should be a problem. The bike also has a hot coil from Colorado Norton works - could there be some false in this which is causing misfiring on one cylinder only? Any and all help would be greatly received.
Thanks in advance,
Paul.



Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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I had similar problems with a Boyer, cure was a dedicated earth wire from head back to positive terminal on battery. Worth a try as not much effort to it.

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Thanks, Kommando. I have several earth/ground wires to the frame and one from the +ve terminal to the head, but it's worth another. As you say, easy to do and it won't hurt anything.
Paul.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
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I'm starting to feel better about my "new-to-me" MKIII still having the original points and coils!

Sometimes those "black boxes" work (the one on my Firebird has been working great for years) and sometimes they don't (the one on my Guzzi Cal III had to be replaced twice) .....

Lannis


It's easier to fool people than to convince them they have been fooled.
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I had similar misfire troubles with the OldBritts powerarc system on my 71 Cdo. The culprit was a bad ground wire to the unit, but the only way I found it was to run a dedicated ground right from the battery to the unit, bypassing the existing harness.


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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Maybe check the valve clearances....


Bill
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1966 Lightning
1965 Lightning Rocket
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I have had the dual output coils do this. it will misfire on one side as it crosses over internally. the coil coil could of been the cause of the trispark failure also.

Originally Posted by Paul Sammut

The bike also has a hot coil from Colorado Norton works - could there be some false in this which is causing misfiring on one cylinder only? Any and all help would be greatly received.
Thanks in advance,
Paul.



windy
72 combat
if it aint broke fix it till it is
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Thanks Bill - forgot to mention in the long list of things I'd done - I had rechecked and adjusted the valve clearances before checking compression. It made no difference.

Interesting to hear you had a similar problem with a dual coil, Windy - I'm ready to try a new one. The thought had crossed my mind that a bad coil could have damaged the module.

Thanks all - I'll let you know how it goes when I get a coil. Meanwhile, any other ideas will be most welcome.

Paul.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
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Paul, it is possible that the wiring has an internal fracture where it goes into the points cavity of the engine.
This is not always visible from the outside.
The motion of the engine in the isolastic rubbers may cause the copper wiring strands to break, and cause a misfire.
I had failed wiring on my Commando at the same spot, and this fault was not easy to detect.



Peter.
1974 Commando 850
1972 Trident T150T
1961 Goldie DBD34
1969 Benelli 250 sport special
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for the last time, his name is not Bill! It's Wendy.

Hi Mike,


Rich
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
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Hi Rich....hows the MG comming along?


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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Haha..... He wishes it's an MG smirk


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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this TRIUMPH ain't got enuf rust to be an mg. and it don't miss and backfire off idle.


Rich
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
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Originally Posted by Richrd
this TRIUMPH ain't got enuf rust to be an mg. and it don't miss and backfire off idle.


Give it time then.......... whistle


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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had this problem before,,,recently on a harley shovel,,,,was always a bad dual fire coil,,,you can put back the original 6 volt coils in series,,or 12v in series,,,{+ to -} for a test

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Thanks, bsatrinor - hope you're right. Just borrowed another 12v coil off Rich to try, before purchasing another. Of course, we took it off his BSA (aka Blonde Bitch) so who knows how it's going to mess up up my lovely Norton smile


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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the dual lead coil worked good on my bike thank you!

but the Diva Norton is still acting up. Next he's going to be wanting to borrow two new carbs.


Rich
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

69 bonney
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and a Honda?
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I notice no updates from Paul, so here's my version.

no difference with the other coil.

the motor will start and idle on the right cylinder. left is dead. pulling up on the left throttle cable does nothing. I can see the pilot system being blocked somewhere, but why won't it kick in on the needle?

pulling up the right side cable will rev the motor and cause the left to backfire.

Only thing left is to light a cigar and go home while he installs a set of old carbs.

Latest report is bike now runs on both sides.

Someone please tell me what would keep a fairly new carb from working on any of the metering systems, (pilot / needle / main)


Rich
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

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Ok, scratch that post.

the bike is back to being a single cylinder. the left will only spit and bang intermittently.


Rich
"It's not always about going fast. Sometimes it's nice to slow down" (Wendy E.2016)

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Now on it's 3rd carb body, the bike still barely fires on the left, except intermittently, and frequently spits back through the carb and bangs in the exhaust.
Swapping float bowls didn't help; all four valves move normally; there is no air leak in manifold or around exhaust headers.
Rich has a useful thought (on occasion, he does) - maybe one of the magnets in the Trispark's rotor is weak. I'd not changed it; only change the stator.
Will see tomorrow if that makes any difference.




Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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Originally Posted by Richrd

Someone please tell me what would keep a fairly new carb from working on any of the metering systems, (pilot / needle / main)


No fuel flow to that carb??


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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A reasonable thought, MikeG, but there's great flow - float bowls fill easily and plug's wet.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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Question - would I have the above symptoms if an exhaust valve spring was broken?
Tomorrow, I will pull the head, but would love to know what I'm looking for, ahead of time (so to speak.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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Well - nothing wrong with the head, valves, tappets, push-rods or cams. Still flummoxed!
Any and all ideas, no matter how weird, gladly considered.


Paul

'74 Commando - Interstate
"74 Commando - Hi-Rider, possibly
'65 Atlas, mostly anyway
'15 R1200 GS Adv
'51 Vincent Rapide
'58 Ariel Square Four
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Paul-quick easy test to make certain if it's a fuel or fire problem. Hook an inductive pickup timing light to the bad cylinder and see it it flashes as it should. At least you will know you've got fire up to the plug. Perhaps you've got a dead cat or something stuck in the points cavity?? whistle laugh


1960 BSA A10
2007 Suzuki Bandit
1957 A10
(Used to be a Triumph here)
71 Norton Commando
17 Triumph Bonneville

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