1974 850 commando trouble SOLVED

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nortonisthebest said:
On my 1972 Norton I had a Sparx electronic ignition system in place of my points. My bike started missing out on one side causing it to run intermittently on one cylinder. I finally located the problem. All electronic ignitions stater plates have two coils wrapped with copper wire. One coil for the left cylinder and one for the right cylinder.
Click to expand...

The system is wasted spark. The stator coils are connected in series so there is no "left" or "right" cylinder coil.
 
krullbeast said:
thank you i will! i hope it's not the head dangit. battery tested good. fully charged
Click to expand...

i re did the compression test and both sides are reading about 130. (better than 90 but not 150) i checked the plugs and the left side is fouling out quickly. i switched the plug wires and it is the same. left side won't fire under load it seems. i took off the valve covers and watched them go up and down as i kicked through. it looks right. i am still confused. thank you for trying to help!
 
illf8ed said:
If you have gas and spark the only thing left is compression. Take the valve covers off, kick through and make sure the valves are openning. After that a compression check. If all is good the spark plugs could still be suspect...replace them and see what happens.
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i did so and they valves are definitely opening and closing. compression reads about 130 on both sides. replaced the plugs and the left side fouls out quickly. any ideas? thank you!
 
Steves said:
I think we have all been here at one time or another. I don't think resistor plugs or caps are suddenly going to be an issue. I would check the plugs see what they look like, put new ones in. Then I would check the carbs from filter to manifold to see if anything amiss. Once that is done start either with carbs or electrics and work your way through. If it is a sudden change it is probably an electrical problem unless you find something amiss with the carb in the first check above. It really is a process of elimination, resist the temptation to overthink it, probably something really simple.
Click to expand...

thank you. i will now try dismantling and cleaning the carb, if i can't figure anything wrong, i will readdress the electrics. i appreciate the info
 
krullbeast said:
thank you. i will now try dismantling and cleaning the carb, if i can't figure anything wrong, i will readdress the electrics. i appreciate the info
Click to expand...
Take off float bowl and see if main jet has come undone and take cap off to make sure needle is in place. These can both be done with carb on bike.
 
Beach said:
Take off float bowl and see if main jet has come undone and take cap off to make sure needle is in place. These can both be done with carb on bike.
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the needle seems to be in place. it goes up as i add throttle and back down as i release. the main jet (a 260) looks fine and i securely put it back, but the problem persists. i checked the spark on that side and it definitely looks weak. my battery tested at 12.8. i switched plug wire sides and the same problem stayed on the left side. i just had newer cans installed when i had the trispark installed about a year ago. i have never had trouble starting it until this problem started. any ideas? thank you for your help! my compression tested at about 130 on each side.
 
Re-reading your original post you say one of the chokes is hanging down. You mean into the bore of the carb? This will cause that side to run rich and cause the bogging down at wider throttle openings. Maybe remove the chokes completely, plug the cap and see if it makes a difference. I run my bike without chokes, in winter takes a couple of mins warming up to pull away, summer no problems.
 
L.A.B. said:
The system is wasted spark. The stator coils are connected in series so there is no "left" or "right" cylinder coil.
Click to expand...

Looks like I need some schooling here. I understand wasted spark, but is not the fire for the left cylinder having to travel through the left coil? It sure looks that way.
And if the left coil had a problem, it seems that wd affect the left cylinder?
OP reports he has "new twin coils"...
 
Last edited:
Switch the coils and see if the problem persists on the other cylinder. If it does then you have a bad coil. Or test with an some extra long hi tension leads crossed to get the same result.
 
Mr. Rick said:
Looks like I need some schooling here. I understand wasted spark, but is not the fire for the left cylinder having to travel through the left coil? It sure looks that way.
And if the left coil had a problem, it seems that wd affect the left cylinder?
OP reports he has "new twin coils"...
Click to expand...

My reply was regarding stator (pickup) coils not being for left and right cylinders. Not ignition coils.
 
Mr. Rick said:
Looks like I need some schooling here. I understand wasted spark, but is not the fire for the left cylinder having to travel through the left coil? It sure looks that way.
And if the left coil had a problem, it seems that wd affect the left cylinder?
OP reports he has "new twin coils"...
Click to expand...

Yes, each ignition coil is for a specific cylinder. LAB's post was with regard to the coils on the pickup stator, which have no association with a particular cylinder.

I have had ignition coils fail on Commandos from over tightening the clamp, which deforms the coil body. This is with stock Lucas coils though, not aftermarket. My Tri-Spark coils are much beefier than stock.
 
Its a good idea to swap the coils, not just wires and plugs.

If you are running stock coils its a good idea to get rid of them due to compatibility issues with the TriSpark.
 
Lee

A couple of checks worth trying.

I'd start by sorting the choke so that it works correctly by adjusting the cable or replacing it.
I've known the nipple break off at the slide end of the choke cable.

Also I've had similar symptoms to yours twice on my Commando when the throttle needle and clip have been 'picked-up' by the throttle slide spring like this:

1974 850 commando trouble SOLVED


Causing one side to run very rich. I've also seen this occur on another Commando.

You'll need to remove the carb to check for this and correct it.

Andy
 
krullbeast said:
<..> i just had newer cans installed when i had the trispark installed about a year ago.
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Battery voltage is OK, but you should check voltage at the left side coil while bike is idling. Maybe you have a drain in the electrical circuit? Bad earthing? I take it you mean "newer coils installed ...". So they were not new? The left side coil may have an internal short, this often happens when clamps are overtightened, and of course with age. The error could occur intermittently with load, heat or vibration. I would definately swap coils with new ones to eliminate this potential error.
Furthermore, you should check your carb and manifold for air leaks. Flatness of manifolds is essential. Flanges warp if overtightened.
Is your petrol tank rusty inside? Debris may have blocked your carb. Fitting an inline petrol filter may be necessary for the future.

-Knut
 
L.A.B. said:
My reply was regarding stator (pickup) coils not being for left and right cylinders. Not ignition coils.
Click to expand...

i swapped out coils and i think i found the culprit. new coil gets here on friday. the bad one didn't get hot though and had no cracks whatsoever. hmmm.
 
mdt-son said:
Battery voltage is OK, but you should check voltage at the left side coil while bike is idling. Maybe you have a drain in the electrical circuit? Bad earthing? I take it you mean "newer coils installed ...". So they were not new? The left side coil may have an internal short, this often happens when clamps are overtightened, and of course with age. The error could occur intermittently with load, heat or vibration. I would definately swap coils with new ones to eliminate this potential error.
Furthermore, you should check your carb and manifold for air leaks. Flatness of manifolds is essential. Flanges warp if overtightened.
Is your petrol tank rusty inside? Debris may have blocked your carb. Fitting an inline petrol filter may be necessary for the future.

-Knut
Click to expand...

thanks! i swapped the coils and it ran bad on the right side, so i'm waiting on a new coil to remedy it. the coils were new, yes, when purchased less than 2 years ago. every flange looks pretty flat, but i will retest for air leaks. i appreciate it
 
DevonNorton said:
Lee

A couple of checks worth trying.

I'd start by sorting the choke so that it works correctly by adjusting the cable or replacing it.
I've known the nipple break off at the slide end of the choke cable.

Also I've had similar symptoms to yours twice on my Commando when the throttle needle and clip have been 'picked-up' by the throttle slide spring like this:

View attachment 6181

Causing one side to run very rich. I've also seen this occur on another Commando.

You'll need to remove the carb to check for this and correct it.

Andy
Click to expand...

thanks andy! i will replace my bad coil first and hope that was the problem, but i can see how that throttle spring issue would be baffling if i didn't fully remove it. i think i'm going to cap off my choke after this. i just doesn't seem necessary, what do you think?
 
rvich said:
Its a good idea to swap the coils, not just wires and plugs.

If you are running stock coils its a good idea to get rid of them due to compatibility issues with the TriSpark.
Click to expand...
thanks rich! i swapped them and it ran bad on the other side, so i'm hoping that fixes it. i appreciate your responses!!
 
CanukNortonNut said:
Switch the coils and see if the problem persists on the other cylinder. If it does then you have a bad coil. Or test with an some extra long hi tension leads crossed to get the same result.
Click to expand...
thank you! i swapped them and it ran bad on the other side. waiting now for a new coil! fingers crossed!
 
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