Update - running like new...

Turns out it was never my carbs that were giving me headaches, it was the alternator (who knew??? Mitch did). I'd installed a Tri-Spark ignition months ago, so since I was now replacing my alternator I decided to switch over to CNW's single coil set up and Wassel 3-phase alternator / Tri-Spark regulator. This seems to have cured all issues. One, two kicks max, and my bike starts and idles with no throttle. It starts and holds at 800 rpms, then rolls up to, and holds at 1000 when warm. Acceleration is even and smooth, deceleration is equally even and smooth - always returning to 1000 rpms at idle.

BIG THANKS go to htown16 who correctly identified the issue I was having with my 73 850 Commando and suggested corrective action. BIG THANKS also to Matt at Colorado Norton Works for talking me through an unfamiliar installation.

I've had the bike for just over a year now. I've replaced all isolastics and head steady. Phil Radford rebuilt my rear brake drum (great job, fair price). I followed My Ty Garage's YouTube video on rebuilding the swing arm, adding the spindle kit from NYC Norton. Replaced all cables. Removed and installed a new Lucas wiring harness, headlamp harness too (lights, turn signals, kill switch - everything works). Drained and replaced all oils and lubricants (twice). My goal has been to make the bike safe and reliable... which I believe it is now.

Thank you Access Norton members for all your guidance and advice.

later dudes... I'm going riding
Chris - San Diego, CA

@Chris Larkin be sure to run an extra earth from your Tri-Spark up to your coil for peace of mind.

90% of all carb problems are electrical.

...and Vice-versa!

90% of all Commandos are probably jetted too rich. If you are jetted lean and have electrical problems . . . ?

gtiller said:

@Chris Larkin be sure to run an extra earth from your Tri-Spark up to your coil for peace of mind.

Click to expand...

The Tri-Spark gets its ground from the engine. It's important to ensure that the ground harness connects solidly to the engine cases (or head).

As I recall, your bike stumbled and ran poorly at low RPM's, which seemed like a rich carb issue. A weak spark can also seem like a richness issue. This should make sense to you... poor spark doesn't burn up all the fuel so the plug looks rich...

Possibly,... you had a weak coil/poorly grounded coil and the new CNW coil alone cured your rich condition at idle and low rpm's. If your battery was good and charged, a weak alternator wont effect the bike until the battery begins to lose it's voltage, so you would only get poor running after the bike ran for a while, especially if you use a battery tender to keep your battery topped off...

My guess is your issue was coil or coil/engine ground related... all the new parts are great too, so no harm in upgrading... I'm glad you got it going well. I know you were pretty frustrated. Good perseverance on your part!!!

@maylar yes I know where the Tri-Spark gets it’s positive supply from.

The harness feeds a positive to the head - hopefully to the engine side of the headsteady, not the frame side.

However, with the exception of electric start bikes, you are wholly reliant on getting a positive supply to the crankcase through paper gaskets, loctite, composite gaskets, rubber washers, tacho cable, paint and powder coat.

It‘s a precarious route and I feel it’s one of the reasons that Tri-Spark gets a hard time , hence my recommendation to run an extra cable from the coil down to the ignition.

gtiller said:

It‘s a precarious route and I feel it’s one of the reasons that Tri-Spark gets a hard time , hence my recommendation to run an extra cable from the coil down to the ignition.

Click to expand...

But the coil isn't grounded. If you want an extra ground it should go to the harness ground. And I agree that it may be why the trispark gets a bad rap.

edit: The coils are indeed grounded on a positive earth machine. But not on negative earth.

gtiller said:

@Chris Larkin be sure to run an extra earth from your Tri-Spark up to your coil for peace of mind.

Click to expand...

I've read about this... where you not only ground the unit on the post, but add / pull an 18 gauge ground wire outside of the contact breaker cover and ground it to the frame. It is a good idea, something I should do.... once I get some miles on this gem... I just gotta ride right now.

Thank you

maylar said:

The Tri-Spark gets its ground from the engine. It's important to ensure that the ground harness connects solidly to the engine cases (or head).

Click to expand...

The main ground is attached to the head - as it was when new.. Thank you

grandpaul said:

90% of all carb problems are electrical.

...and Vice-versa!

Click to expand...

I'm learning this... Thank you

o0norton0o said:

As I recall, your bike stumbled and ran poorly at low RPM's, which seemed like a rich carb issue. A weak spark can also seem like a richness issue. This should make sense to you... poor spark doesn't burn up all the fuel so the plug looks rich...

Possibly,... you had a weak coil/poorly grounded coil and the new CNW coil alone cured your rich condition at idle and low rpm's. If your battery was good and charged, a weak alternator wont effect the bike until the battery begins to lose it's voltage, so you would only get poor running after the bike ran for a while, especially if you use a battery tender to keep your battery topped off...

My guess is your issue was coil or coil/engine ground related... all the new parts are great too, so no harm in upgrading... I'm glad you got it going well. I know you were pretty frustrated. Good perseverance on your part!!!

Click to expand...

Your recollection is correct... all problems seemingly pointed to the carbs as the issue. What I couldn't wrap my head around was having such dramatic issues with the carbs when they were brand new. - and cleaned / inspected twice.

When I upgraded to the Tri Spark ignition, I installed new coils, plug wires, resistor plugs and new battery. With a fully charged battery and cleaned plugs I was able to ride (stable idle too) for 30 or so minutes before it went to crap. That's when htown16 said "have you looked into your alternator?" He suggested testing, but I'm too impatient (plus the og equipment is 47 years old) so I swapped it all out for the single coil and three phase alternator / regulator I have in now.

Right now - one kick, no throttle, and it starts perfectly. I rode for 90 minutes yesterday with zero issues, a solid 1000 rpm idle, smooth acceleration and deceleration (no coughs, wheezes, spits or blaps) - plus reaching 80 mph with plenty of throttle left.. zooooom.

You were a big help to me too... pardon my for not giving you a proper shout out...
THANK YOU o0norton0o

Chris Larkin said:

The main ground is attached to the head - as it was when new.. Thank you

Click to expand...

When new, the ground connected to a bolt on the head steady mount, and as Grant noted that can be precarious. Corroded fasteners, painted or powder coated head steady bracket etc can be iffy. The frame is not technically a ground either, as the ground wires connect to the right hand Z-plate near the zener and to the coil mounting bracket for the points ignition condensers/capacitors. All of these connections are subject to age failures. That being said, I had the stock ground wiring for over 40 years without any problems.

maylar said:

The frame is not technically a ground either, as the ground wires connect to the right hand Z-plate near the zener and to the coil mounting bracket for the points ignition condensers/capacitors.


All of these connections are subject to age failures.

Click to expand...

The frame isn't ground as you say, however, "the ground wires connect to the right-hand Z-plate" could be misinterpreted to mean that the Z-plate is some form of ground point for the electrical system so just to make it clear, the red wire connected to the right-hand Z-plate provides a ground connection (to harness red) for the Zener diode, therefore, under normal circumstances, the Z-plate doesn't require an electrical connection to the frame as the red wire attached to the Z-plate is the 'ground' but could provide a secondary ground path through the frame to another red wire attachment point in the event of a Z-plate red wire failure.

That's true, and even though there are 3 bolts joining the Z-plate to the frame that wire was not intended to be a frame ground. As far as I know, the only intentional frame ground was to the condenser pack. We do need a frame ground for the rear blinkies.

maylar said:

That's true, and even though there are 3 bolts joining the Z-plate to the frame that wire was not intended to be a frame ground. As far as I know, the only intentional frame ground was to the condenser pack. We do need a frame ground for the rear blinkies.

Click to expand...

Yes, although the actual frame connection to 'ground' would normally be either a ring terminal or spade tab at the rectifier.

You will notice the main symptom was that the bike ran well for about 30 minutes then started running poorly. I had a similar problem on my Trident and found a severed wire from the alternator. 30 minutes of riding is about the amount of time that it will take to discharge the battery without the alternator charging even if the battery is new and has been on the charger. Chris also reported that turning the headlight on and off made the running worse. Another sign of the voltage going to the ei being marginal.
Kudos to Chris for hanging in there and solving his problems.

maylar said:

... And I agree that it may be why the trispark gets a bad rap...

Click to expand...

Trispark isn't getting any worse of a rap as any of the others.

Over several years that I've been paying some attention, I started out bad-mouthing Boyer ignitions because I found so many failed ones on old bikes I restored. That was somewhat supported by general comments on several forums I've been on.

About 6 or 8 years ago, I started hearing an increasing number of negative reports about Sparx ignitions (that did not comport with my personal experience of several dozen units installed by that time).

Over the last 5-6 years, I've been hearing more and more tales of woe regarding Tri-Spark ignitions.

What this has all "boiled down" to (in my mind, at least), is that there were more failed Boyer ignitions out there because for quite a number of years, that was THE most popular ignition on the market, and with THAT many installed units, the odds of individual failure had to be higher, even if the "per-capita" number of failures was actually LOWER.

When the installed base of Sparx units reached a high enough number, the failure rate started becoming significant enough that reports filtered into the internet.

Same goes for Tri-Spark. With the significantly higher price of Tri-Spark units, it just took them longer to get to "critical mass"...

grandPaul - very much enjoyEd your book!

The sparks issue was very real. The spacing and positioning and the way it interacted with the mounting bolts and Rotor was not right. At least in the 3 units I installed. I have had boyers that lasted for decades but out of the box the sparks stator / rotor was a poor product. that was true in 2010-12 when they knew there was an issue and replaced units without question before stopping making the product.

grandpaul said:

Trispark isn't getting any worse of a rap as any of the others.

Over several years that I've been paying some attention, I started out bad-mouthing Boyer ignitions because I found so many failed ones on old bikes I restored. That was somewhat supported by general comments on several forums I've been on.

About 6 or 8 years ago, I started hearing an increasing number of negative reports about Sparx ignitions (that did not comport with my personal experience of several dozen units installed by that time).

Over the last 5-6 years, I've been hearing more and more tales of woe regarding Tri-Spark ignitions.

What this has all "boiled down" to (in my mind, at least), is that there were more failed Boyer ignitions out there because for quite a number of years, that was THE most popular ignition on the market, and with THAT many installed units, the odds of individual failure had to be higher, even if the "per-capita" number of failures was actually LOWER.

When the installed base of Sparx units reached a high enough number, the failure rate started becoming significant enough that reports filtered into the internet.

Same goes for Tri-Spark. With the significantly higher price of Tri-Spark units, it just took them longer to get to "critical mass"...

Click to expand...

Yes ,it's a per - Capita , number of units being used thing. Of course there were more failures because most units sold were that. I dumped my early Tri-Spark and purchased a Boyer MK 1V unit and have been happy ever since.