running like crap - 2000-3000 RPM - a bit stumped and not sure where to go

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Have you checked static and operational voltage as gortnipper suggested, especially at the RPM range where things go sideways? Have you done a plug check after being in the RPM range for about 30 to 45 seconds as Torontonian suggested?

The suggestions made by the members who have contributed to this post are all good, but should be done one at a time.

If the static and operational voltage readings are as gortnipper outlined, my suggestion would be to tighten (or slack) the ISOs and see if the issue occurs at a different RPM range. This would indicate carburation as DynoDave mentioned.

Any EI likes a good ground and a power path, if either the supply or the ground is not doing it's part the issues mimic each other. If the harness is original and the wires are brittle patching the bad sections may solve the problem, but not for long, and Lady Luck may well cast you adrift on some lonely back road when your mates are ensconced, social space permitting, in your favorite pub mikes away.

In which case the best set of tools to carry are your cell and credit card.

Best.
 
The curiosity part of this situation to me is that electrics (whether primary or secondary) don't usually fail in the middle of an RPM range while working correctly above and below that range. That's why it strikes me as some sort of vibration-related thing since the Norton vibrates considerably in the range described. In any case, it will be very interesting to find what the actual problem is!
 
RoadScholar said:
In which case the best set of tools to carry are your cell and credit card.
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If you can't get any mobile phone reception, and the breakdown people haven't got any bank details then it's sod's law you are out on a limp in the middle of nowhere. . . . .
 
Bernhard said:
If you can't get any mobile phone reception, and the breakdown people haven't got any bank details then it's sod's law you are out on a limp in the middle of nowhere. . . . .
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Good point. So consider adding camping gear and the means to start a fire to send smoke signals; naturally you'll need to carry food and water, perhaps enough of your favorite spirit to drown your sorrows, maybe rent a sat-phone?

running like crap - 2000-3000 RPM - a bit stumped and not sure where to go


Such preparation would seriously dampen any desire for a spirited ride in unknown territory. As has been mentioned many times: A motorcycle ride isn't an adventure until something goes wrong.

Makes a good case for taking any repair a few levels beyond the obvious failure point.

Best.
 
That image you supplied looks like someone who is going around the world......but looks like they're forgotten something.....kitchen sink perhaps?
 
FWIW, I rode a Commando as my "only vehicle" for several years back when they made Commandos. I never carried any tools/other articles. Just put on my office work clothes (suit/tie), added a jacket, helmet and gloves, and rode the 12 miles to work, back in the eve. On weekends I rode to the local race track and attempted to compete/got my racing license. I was not all that successful as a racer but the bike never let me down.
 
Bernhard said:
That image you supplied looks like someone who is going around the world......but looks like they're forgotten something.....kitchen sink perhaps?
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Swiss bike by the looks of it - Not surprised.
 
Craig said:
What is your new R/R supposed to do , you have already proved that your present R/R (podtronic) is functioning as it should ..... do you expect divine intervention ......
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don't know, probably nothing. the new R/R is just an upgrade i've been wanting to do for some time now. haven't had much time to devote to the commando - busy on my 66 Spitfire restoration project. rest assure, i will test the podtronics unit. i ordered a mosfet R/R and tri-spark for the Spitfire, so i just added in an additional R/R. ...and, no on the intervention.
 
So sorry Joe. These old Nortons, or any old British bike; can make you pull your hair out, what with all their frustrating "niggles." ... and seemly endless troubles. Like most modern electronics (I work on FAA Radar displays and servers that generate the display data, and they can have some very oddball, solid and intermittent electronic problems. And then fixed by you guessed it, swapping with "known good" parts.) So, you may have to just start "swapping parts" … with know "good" if possible. Can be expensive, but you want it running right.

Since it is a solid problem, and appears at a specific resonant frequency, you have to start eliminating possible "electronic" suspects. If it were mine, I would switch to the ORIGINAL type contact breaker points, and the AAU. Ride it and troubleshoot from there. Just my 2 cents ...
 
nortriubuell said:
So sorry Joe. These old Nortons, or any old British bike; can make you pull your hair out, what with all their frustrating "niggles." ... and seemly endless troubles. Like most modern electronics (I work on FAA Radar displays and servers that generate the display data, and they can have some very oddball, solid and intermittent electronic problems. And then fixed by you guessed it, swapping with "known good" parts.) So, you may have to just start "swapping parts" … with know "good" if possible. Can be expensive, but you want it running right.

Since it is a solid problem, and appears at a specific resonant frequency, you have to start eliminating possible "electronic" suspects. If it were mine, I would switch to the ORIGINAL type contact breaker points, and the AAU. Ride it and troubleshoot from there. Just my 2 cents ...
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Your statement still makes me think you have disregarded the nonlinear air flow cylinder pressures and carb throttle setting nonlinear F/A ratio. Going directly to electric power/electronic as cause, rather than effect, without testing can lead you down the path to continued confusion. Now we are at post 51 with no end in sight.
post# 23 clean hot plug test? = fuel problem or not? swap in good carbs?
I've seen it many times but YRMV
 
MexicoMike said:
The curiosity part of this situation to me is that electrics (whether primary or secondary) don't usually fail in the middle of an RPM range while working correctly above and below that range. That's why it strikes me as some sort of vibration-related thing since the Norton vibrates considerably in the range described. In any case, it will be very interesting to find what the actual problem is!
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Agree , to rule out electrics in part, a simple test is to turn petrol off , as it is happening , if engine revives then I would look to vibration causing flooding at float needles
 
oldmikew said:
Agree , to rule out electrics in part, a simple test is to turn petrol off , as it is happening , if engine revives then I would look to vibration causing flooding at float needles
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I was going to say "frothing"... similar result
 
Leaving in bad/border line fouled plugs and trying to determine if a carb fault seems like very flawed trouble shooting.
I receive dozens of crappy plugs to run in my various nortons which cleans them, and fully restores smooth running. They go in dirty and come out burned clean.
Last set of plugs I bought was over 30 years ago.
reduce reuse recycle plugs
 
dynodave said:
Your statement still makes me think you have disregarded the nonlinear air flow cylinder pressures and carb throttle setting nonlinear F/A ratio. Going directly to electric power/electronic as cause, rather than effect, without testing can lead you down the path to continued confusion. Now we are at post 51 with no end in sight.
post# 23 clean hot plug test? = fuel problem or not? swap in good carbs?
I've seen it many times but YRMV
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Post #2 "What do the plugs look like?"
 
Schwany said:
Post #2 "What do the plugs look like?"
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Well yes in a way I agree. However the actual carbon and residue is constantly changing based on throttle opening affecting the plug tip temperature which changes, therefore the carbon and residue coverage up and down like surf at the ocean. A blast up the highway can clean up the plug for smooth running then returning to a low throttle run bring the misfire back relatively quickly with very bad carbs. (rich cutaway or worn out needle jet)
On the dyno I have seen sub 900 degrees which blackens the plugs. Then same bike WOT to 1350f EGT which in very short order will make the plugs screaming white clean.
 
dynodave said:
Well yes in a way I agree. However the actual carbon and residue is constantly changing based on throttle opening affecting the plug tip temperature which changes, therefore the carbon and residue coverage up and down like surf at the ocean. A blast up the highway can clean up the plug for smooth running then returning to a low throttle run bring the misfire back relatively quickly with very bad carbs. (rich cutaway or worn out needle jet)
On the dyno I have seen sub 900 degrees which blackens the plugs. Then same bike WOT to 1350f EGT which in very short order will make the plugs screaming white clean.
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Yes, that's how it all works, but one should already know that shouldn't they? Kidding, I wrongly assumed too much tuning knowledge on the part of the OP. Kinda of silly on my part. Anyone with tuning knowledge wouldn't be stumped or looking for help here. A plug chop (How do the plugs look?) at 2800 RPM should work to identify the rich condition. Plugs should start to clean up above 3000 RPM according the the described symptom. But who knows what's really going on. Only real way to be of any help would be to have somebody ride the bike that knows Nortons, or any old carbureted twin.

My Norton shows exactly what you are talking about. With the big 35mm Keihins on a little 750, extended idle and blipping for say 15-20 minutes checking out one thing or another creates black velvety carbon on my plugs with just a little fuzzy white ring on the tip of the center electrode. If I get out and ride it with a load on the motor and occasionally hold a gear and turn the wick up, all that carbon gets burned off and the plug actually looks like I'm running on the lean side. That said I'm running with Autolite 5224 plugs for grins. A tad more tip projection than the commonly used plug, but they are working well enough so far.
 
joe czech said:
don't have vast experience on these old twins but i don't think it's carb related, but leaning toward electrical and and maybe frequency dependent. need some help and comments. TIA....
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Joe, any updates? A lot of good ideas; any progress?

Best.
 
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