Absolutely mystifying failure, 850 Commando Mk III

Having busy day so can't answer in detail but I had a similar set of symptoms including swapping plugs over. It was the trigger unit on one side. You see spark on both plugs but one is the wasted spark and the firing spark for that cylinder is not working.
 
dobba99 said:
Had similar when called to look at a commando that displayed similar symptoms. The owner had sleeved the coils with a thin rubber sleeve so the earth path was compromised.
Click to expand...
Earth path?? Ignition coils are essentially step up transformers. Wire wrapped around iron cores. I have seen coil housing crushed by the clamps and resulting in the housing shorting out the coil, but normally the coil housing is not grounded. The rubber sleeve might have solved that issue.
 
Ron L said:
Earth path?? Ignition coils are essentially step up transformers. Wire wrapped around iron cores. I have seen coil housing crushed by the clamps and resulting in the housing shorting out the coil, but normally the coil housing is not grounded. The rubber sleeve might have solved that issue.
Click to expand...
Yes, earth path. The other end of the high tension circuit. One end is the plug lead to spark plug and the other end goes to the coil housing, then coil bracket, frame and back to the engine and spark plug body. Sleeving the coil with a rubber sheet had effectively insulated the coil, making it work much harder
 
Baring a catastrophic internal engine failure, the only thing that can stop the bike running as if it was shut off is electrical. Carbs running out of fuel sputter a bit before shutting the cylinder(s) down.

I have seen ignition coils do weird stuff. The strangest was a car's ignition that would temporarily shut down if the car was in an aggressive left turn. It was fine under any normal driving conditions but if pushing it hard into a left turn the ignition would cut out and then come back in as the speed reduced.
 
dobba99 said:
Yes, earth path. The other end of the high tension circuit. One end is the plug lead to spark plug and the other end goes to the coil housing, then coil bracket, frame and back to the engine and spark plug body. Sleeving the coil with a rubber sheet had effectively insulated the coil, making it work much harder
Click to expand...
Nonsense, on a T 120/140 O.i.F. the coils are sticking only in rubber without any connection
to earth ! Without any problems in decades !
 
Being wasted spark: Have you swapped both HT leads and spark plugs together, as a unit? If it still fails on the right, doesn't that rule out ignition?
 
Have to agree with the thought that it is electrical due to sudden loss. Ohm test the coils separately, off the bike. Sometimes they can be just inside the design parameter and give trouble. Happened to me a few months ago.
Any chance you can BORROW a Pazon plate and rotor? If that makes a difference you might be able to recover some
of your investment with the seven year Pazon warranty.
Hate to be a parts changer but sometimes it is useful to entirely eliminate possibilities.
 
From their website:

CHECKING THE ROTOR

There is little to go wrong with this part, provided it is fitted correctly.
Excessive wobble of the rotor can give symptoms that include not running on all cylinders (on multi cylinder engines), mistiming and/or misfiring.

Altair

Pazon Ignitions. Electronic ignition systems for classic motorcycles, digital & analogue, Triumph, Bsa, Norton, Enfield, Velocette, Vincent & more.
www.pazon.com www.pazon.com
 
Both Boyer and Pazon state in their fault finding procedures that a failed unit will stop both sparks and any fault that only affects one side is nothing to do with their equipment. As the box is essentially a simple on/off switch that follows the signal from the magnets passing the coils on the stator that is strictly true. But wasted spark is putting more load on the harness and all the equipment with double the sparks. As in my case where the earth route from head back to battery was only good enough for one spark not two. For a reason I never found I lost the spark on one side, only two conditions got it back on that side, removing the HT lead from the spark plug on the good side or a dedicated wire from head steady back to battery.
 
Lannis said:
I appreciate every comment and suggestion so far.

I certainly don't want to insist that my testing has been exhaustive or done absolutely correctly, because the bike isn't running and something is wrong, so I don't want to fall into the trap of "defending" my troubleshooting.

The carb swap was "tight" but the carbs settled onto the flange and appeared to seal up with no interference. The balance tube is in place. Both carbs will run the Left side properly ... neither carb will run the Right side.

Coils are wired in series, and I have swapped them, the plugs, and plug wires separately.

The right side quit running on the highway at cruise like a switch had been cut off, and has not run since in any way except for the occasional pop. Both spark plugs are firing together on each upstroke (as evidenced by the spark detectors).

I have removed the right side silencer and run it; strong pulses coming through on each power stroke, but no power.

The valves are operating properly; the compression tester (at WOT) shows 75 on the first stroke, 125 on the second, and 175 on the third, exactly like the left (running) side.

If I hold the tickler down, fuel splashes out of the carb bowl as long as I hold it down, and stops dead when I let go of the tickler, so fuel is flowing. Both carbs act the same when connected to the non-running side in that respect.

Assuming it is an ignition failure with the Pazon, either on the circuit board or in the timing chest wiring .... What kind of failure mode would result in the right side never firing on time no matter how I swapped the coil wiring around?

Thanks!!

Lannis
Click to expand...
It is weird as it is a dual Spark.
I was thinking a bad resisitor, wire or connection at the plug cap.
But, you say you've switched them?
Just so we know, which Pazon is it?
 
kommando said:
Both Boyer and Pazon state in their fault finding procedures that a failed unit will stop both sparks and any fault that only affects one side is nothing to do with their equipment. As the box is essentially a simple on/off switch that follows the signal from the magnets passing the coils on the stator that is strictly true. But wasted spark is putting more load on the harness and all the equipment with double the sparks. As in my case where the earth route from head back to battery was only good enough for one spark not two. For a reason I never found I lost the spark on one side, only two conditions got it back on that side, removing the HT lead from the spark plug on the good side or a dedicated wire from head steady back to battery.
Click to expand...
I have read where a plug may spark in the open but not under compression.
I've also read where these dual/wasted spark units with two coils travel differently.
One plug sparks for the electrode to the ground, the other from the ground to the electrode.
There may be some validity in a weak ground...
 
MichaelB said:
There may be some validity in a weak ground...
Click to expand...
Lannis has a MK3, for the starter to work there must be a good earth path from starter to battery with those big fat starter leads, so in this case its unlikely but we could have an issue with a helicoiled spark plug hole in the head.
 
Hes swapped coils, he's swapped plugs, he's swapped leads, he's tested for spark under compression- now Im curious- for all those saying its ignition, what is left for him to verify?
 
The test results indicate that the engine should be running perfectly. :rolleyes:

I don't know anything about specifically testing a Pazon unit/its individual components. Do you have another E-ignition or the OEM points/AAU you could try?
 

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