Can't accelerate over 2'000 rpm

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Marcel

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Hi there

Went for a ride today. Weather was quite hot over 30 °C. Norton Commando MK III with tri-spark ignition and standard amals. Normaly starts on first kick and idels steadely below 800 rpm. No problems for the last few years. After riding for about 2 hours I had a loss of power and couldn't rev her over 2'000 rpm. Starting her again was not a problem, but without trottle she would die shortly. Finally managed to get home at speeds of max. 30 mph.

Now where to start finding and solving the problem? Electronic ignition, carbs?

What would you recommend?

Greetings
Marcel
 
Sounds like you may have been riding on one cylinder. A bad coil maybe? Spark Plug bad?

Check for spark on both sides. If you get spark on only one side, swap the wires to the coils and see if the issue follows the coil.

If after a full cool down, all seems well, you could have a coil that is failing when it heats up. I had one on another bike and I could ride about 20 miles and it would start to fail. Let it cool and I could continue.
 
Cdo's will pull highway speed on one jug, just rougher less power is all.
Trisparks reported over heated but why yours now, naw.
Suspect air leaks like carb bowls to manifold stuff.
Suspect vibration sensitive conduction path,
Suspect crap in fuel tank or bowls.
Suspect need new plugs now regardless.
Suspect you were feeling too smug on a fine runner prior.
 
Check battery and charging system. (quite possible)
Check for fuel flow. (not likely)
Check to see if a needle dropped. (somewhat possible)
 
Remove the air cleaner and have a feel for the carb slides and needles while twisting the throttle. My brother had a problem once where a sleeved slide had come unsleeved..
 
I doubt the trispark is the problem

there were a few early ones who had a bad plastic mold mix that under very high heat would allow internal wire fracturing, at least was some amateurs opinion a few years ago, and trispark did acknowledge a couple with mad molds

the trispark is self grounding and if there is a loose or intermittent ground this can cause internal interruption

always make sure your trispard is nipped solid in place inside the points cover, also that you have an extra thick wire ground from a good motor mount to a clear frame bolt location, ground ground ground, can't have too many!

I run my trispark Commando in 100 degree plus temps here in the desert SW with no extra points cover venting and have had no issues
 
Check that the choke lever hasn't loosened up and allowed the choke slides to drop. Happened to me once, I spend a lot of time, energy and money trying to fix the problem. Finally one day I noticed the choke lever had slipped allowing the choke slide to drop into the venturi. Tightened up the screw in the center of the lever, opened them up, and problem solved. Remember that open is with the cable pulled tight, unlike most other chokes...
 
Thanks for all the hints.

Just did some examination...

There was some oil in the electronic ignition; so I cleaned that out.
Spark is fine. Battery also.
Dismanteld the carbs; they look quite clean.
The rubber connection between the airbox and the carb was loose.
The hint with the chokelever was excellent! Maybe just that was the real problem! Tightened the screw and will put the carbs and everything together hopefully by tomorow.

Will report later...

Marcel
 
Sounds to me like your enricher slides are down. Pull the cable all the way tight to pull 'em all the way up. Pull the air filter and MAKE SURE they are indeed all the way up be opening the throtle and ensuring that they are fully up inside the slides when fully open.
 
The only thing I found when I forget to take the air valve (choke) off is that it bogs down with hard acceleration. Otherwise it seems to run fine. I learned that one day riding home and wondering what was wrong.

Dave
69S
 
I know everybody's been pointing to carb issues but it seems the onset was so abrupt and with the high ambient temps after years of trouble free riding..so I'm going with electrical. The TriSpark would be number one because it has a history. I don't know if all of the problems they've had are transient so they clear when the bike has had a chance to cool or not. Did you get a chance to ride the bike after you got home before you worked on it? Whether it's the TriSpark or not, I like to rule out electrical possibilities first because it's either right or wrong.
 
Problem possibly solved. Rotor looks like this:
Can't accelerate over 2'000 rpm


Is there a magnet missing, isn't it?

Greetings
Marcel
 
Problem solved :D :D :D

Found the little magnet, was just slipped to the back side. So applied some glue and hope it will stay on place!

Greetings from Switzerland and thanks for your help.

Marcel
 
Is this one of the new reliable alternatives to the Boyer ? On the bright side, Marcel, you can now add to your c.v. - "Manufacturer Development Tester, Electronic Ignitions". :)
 
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