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Commando Mk2a only runs for about 5 minutes only and then stops

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The bike starts fine, but only runs for about 5 minutes and stops. After sitting it once again starts, but stops again. Anyone with an idea about this.

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Check the breather on the petrol tank, if the tank is not full open the cap and see if the bike runs straight after it stops. Next would be to check the taps flow enough, some have a rubber seal than expands and blocks the flow, drilling a bigger hole fixed that one. Next is electrical e.g. a hot coil, do you get a spark straight after it stops.

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Air: Are the choke slides up?

Fuel: Is the fuel supply good? Both out of the taps (fuel filters in tank may be blocked) and in the carbs (i.e. are the float needle jets blocked)? If when it stops you immediately turn off the fuel taps, are the pipes empty? Are the float bowls empty?

If the tank is very full, is the vent blocked? If you open the filler cap does it restart more quickly?

For ignition related possibilities,  please let us know ignition type.

Also, is this running on the street or just idling? Does it instantly stop or more slowly shudder to a halt?

Regards, George 

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Hello there  is a Commando forum on this web site this forum is for Heavy twins with the Featherbed frame or the diamond frame ie  model 7  and Model 77 600ccAnd Nomad 500/600cc and Not To forget the 1950/1Model 77 ridged 500cc export yours Anna j

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It has boyer electronic ignition and it happens running on the road.

Thank you Anna for your pertinant observation. I am doing this for my technophobe friend and am not familiar with such technicalies. Sorry.

 

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Boyers can be susceptible to the ignition pickup wires internally fracturing causing the problem you describe. Try wiggling them and see if the problem occurs.

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In addition to the well documented internal fractures in the leads, I had a fracture in one of the pickup coils. It did exactly as described - the bike would run for a short while, then stop dead, then start again after a rest. It looked as if the two ends of wire were making contact when cooler then going open circuit as the engine ran and things heated up again. Try a replacement pickup plate and/or run the bike until it stops then quickly get a meter onto the leads and look for an open circuit.

Fuel problems will usually present as a faltering before the engine stops; an electrical fault will usually cause an instantaneous stop.

 

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