Commando 850 1974 misfiring

Hi Philippe,

First question is do you have electronic ignition ? If so which one (Boyer / Pazon etc.)

Tony

Previously philippe_perreault wrote:

Hi guys,

I am new here and in the Commando's World I will try to explain the better i can my problem.

When I start my commando, everything goes well, starts at 1st kick. But after a couple of minutes, like 10 or 20, when i am at normal speed, or when i accelerate, the bike begins to misfire, but not every time, only at every 2 or 3 minutes, and she does it randomly.

And when i am at hight speed, she seems ok. Do you know what goes wrong, my sparkplugs are new, my bike as a single carb with no pushing buttons to tickel, only a choke lever.

thanks!

Hi Phillipe

Tony's questions is relevant. if you have electronic ignition, eg Boyer, there are two wires in the stator (where the points used to sit) joined to the wires leading from the ignition box. not infrequently one or other of these wires seperate due to vibration. You cannot see this as the outer plastic covering remains intact. As the engine warms the covering expands and seperates the inner wire. Not always enough however to stop the spark partially passing through. The best and easiest test is to take out a plug, switch the ignition on and waggle the wires on the stator. If there there are sparks at the plug you have found your problem. Sticking with ignition, another less common problem, but it happened to me recently, is that if the magetic rotor unit behind the stator moves (it shouldn't it's generally very tight), if this happens the ignition timing will be affected but the engine may well start cold and run ok at high speeds.

Tim

I assume you are running a singleAmal Mk1 32mm carb.

My Mk 3 has this set up with the 750 paper air filter, also a Boyer. I have had this carbset up since 2004. At first, flat spots etc were really bad but gradually and with advice from John Dunn it is almost running right.

The best movewas to fit a 260main jet and to raise the fuel level on the stay up float.

Apart from sometimes pulling back etc above 2,300 ishRPM it is clear once you get near 3,000 and smooth all the way up.

My next move is to raise the fuel level a fraction more, then check the banjo filter. If any 'crud' in there then I'llfit an inline filter. If none of that works then I'llmove the needle to the bottom notch. (Slightly richer)

Make sure you have the 4 ring (not 2) needle, designed for 850 Commando's and the correct spray tube.(Again, for 850 Commando)

Taken all this time coz too much time spent riding singles and working out the knocking noise on the 650....Still on with that..

They can be made to work well though.....Good luck.