Commando Quits

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Hello everyone. My first post here.
I’m working on a interesting problem with a ‘71 Commando production racer. The bike is very original, one owner, low mileage, never raced. These days it gets ridden 2-3 times a year. In the last few years the bike will start and run fine but come to a dead stop after about 10 miles. It can’t be kick- or bump-started until it sits for 30 minutes or so. Then it starts and runs fine again. This is surely an electrics issue as there’s no fuel starving exhibited when it halts. The bike is well tuned - timing,plugs, air cleaner, etc. After several episodes of this the owner put a Boyer Mk III ignition on the bike. So now it starts more easily but still exhibits the same problem.
Before I replace the entire wiring harness or something equally drastic, has this happened to anyone else? 2MC capacitor nor zener diode have ever been replaced but symptoms don’t seem to reflect failures there. Battery is fresh and charging system is working properly.
Thanks in advance.
 
Hello everyone. My first post here.
I’m working on a interesting problem with a ‘71 Commando production racer. The bike is very original, one owner, low mileage, never raced. These days it gets ridden 2-3 times a year. In the last few years the bike will start and run fine but come to a dead stop after about 10 miles. It can’t be kick- or bump-started until it sits for 30 minutes or so. Then it starts and runs fine again. This is surely an electrics issue as there’s no fuel starving exhibited when it halts. The bike is well tuned - timing,plugs, air cleaner, etc. After several episodes of this the owner put a Boyer Mk III ignition on the bike. So now it starts more easily but still exhibits the same problem.
Before I replace the entire wiring harness or something equally drastic, has this happened to anyone else? 2MC capacitor nor zener diode have ever been replaced but symptoms don’t seem to reflect failures there. Battery is fresh and charging system is working properly.
Thanks in advance.
Have you checked the plugs for soot? I had Norton do the same thing and it had worn out needle jets. I also checked everything electrical before finding the problem.
 
Coils maybe over tightened , heat expansion cause failure ?
 
I installed a Wassell ignition last year & had developed some missing at higher revs. along with engine shutting down when hot. Anyway installed some new coils and the shut downs vanished only leaving minor missing for trouble shooting. Mine also started right up after a cooling period, but since there were multiple issues I can't just point the finger at the coils though I believe they were complicit. My spark wasn't very intense and with the new ones it is very bright.
A pair of coils is not expensive and goes a long ways in eliminating the items from the list, and taking their age into consideration is another factor making them suspicious.
 
Boyer Mk 111 requires either resister spark plugs such as NGKBPR7ES with the R being resister or resister plugs wires

did the previous owner also do this in addition to installing the new Boyer?

also, is the Boyer mounted in a location of good air flow?
it can shut down in self defense if overheated and 10 miles can do that

just some ideas
 
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Boyer Mk 111 requires either resister spark plugs such as NGKBPR7ES with the R being resister or resister plugs wires

Boyer MkIII DOES NOT require resistor caps, plugs or wires/leads.

http://www.boyerbransden.com/faq.html
"Why Do I Need To Use Suppressed Plug Caps?
MKIII and MKIV do not require suppressed plug caps for operation although we recommend using supressed 5000 ohm plug caps. Micro Digital and Micro Power units must be fitted with supressed plug caps. Plug caps fitted with suppression resistors are usually fitted to prevent radio interference. Radio interference (noise) can cause more complex electronic circuits like radios and computers to malfunction."
 
I stand corrected, suppressed and not resister as I wrongly stated

thanks for that LAB, I thought they were/did the same thing
 
I stand corrected, suppressed and not resister as I wrongly stated

thanks for that LAB, I thought they were/did the same thing

The Boyer MkIII (or MkIV) doesn't require resistors (caps, plugs, leads) for suppression.

http://www.ngksparkplugs.co.za/products/ngk-resistor-caps/
"Plug covers are manufactured to suit many applications and many are of the resistor type which provide electrical noise suppression across all frequencies whilst engine performance is not adversely affected."

So, resistors are recommended for MkIII & MkIV but they are not required.
 
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Yup , I have Boyer mk4 in use no suppression/resistor in circuit ,works great with champion or NGKBP7es plugs ,
 
Was the points ignition in use before the Boyer? If yes, then a coil problem would have affected only one cylinder. The only thing common to both cylinders would be the ballast resistor (not used with EI) and the kill switch.
 
I had a similar problem on the Trident. Run good for about twenty minutes or so then splutter out. Turned out wire from alternator was down to a few strands at connection. Would start out with full charge off charger but battery would gradually run down. Given a little time to recharge itself it would eventually restart. Take a voltmeter with you and check battery voltage when it has the problem or else give the charging system a good checking over.
 
Both the coils on my bike had been equally overtightened by previous owner .... have seen same thing on another bike both coils squeezed way too much .... just sayin coils “could” be problem , similar symptoms only after hot would they fail ..
 
Don't know whether your running an ammeter or not but I had the same issue and it was caused by a defective unit. Easy enough to bypass if you need to check it.
 
Thanks all for the good brainstorming. The weird thing about this is that it's happened for several years, and happened when the bike ran on points/old coils and then again after the Boyer and new coils were installed.
Regardless, I'm going to check coils, even though they were installed new with the Boyer box. I will also give the charging system a thorough going over, starting with the voltmeter check for proper charging, then maybe have a good look at each connection in the charging circuit. I'm intrigued with the suggestion of the kill switch so that will also get a thorough look.
Thanks again.
 
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