what the heck.....????

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Sep 19, 2007
My 850 commando starts only on 1 cylinder and when I attempt to ride the bike, it occasionally fires on 2 cylinders ( brand new Boyer and new spark plugs/cables).
This night I discovered that when I pull the left hand side sparkplug cover from the spark plug and let it just sit loosely on top, it fires on 2 cylinders ????
I rode it for 40 miles with no problems, but as soon as I push the spark plug cover on the spark plug again it only fires on 1 cylinder....

What the heck?????????

Josh in Calgary, Alberta.
Might be one of the new plugs is bad. Try switching the plugs and see if the good/bad cylinder reverses.

Leaving a small gap from the plug cover to the plug is an old trick to create a bigger spark to get a partially fouled plug to fire which seems to be what you experienced.

Careful doing that with a Boyer though as I understand the Boyer should always be grounded via the plug. Not sure if doing that could hurt it or not.

Good luck, hope it is something simple.


Just what I was getting ready to mention, for some reason pulling the cap off the plug seems to give a bit of a kick sometimes. But not always. His question jolted a very old memory of such symptoms. Good answer!
Think cable too. Reverse these also if plug reversal doesn't help.
If I am not mistaken the system is a wasted spark set up so both sides fire whether they are on ignition stroke or not. so you can reverse everything in sight in the hunt for the culprit.

Thanks for your advice. I replaced the suspect NGK spark plug for another brand new one and problem is solved! Weird that a new plug can do that!!
time for some riding now... Thanks.
You could also have a weak coil on the "bad" side. Fitting new plugs enables the weak coil to fire on the power stroke but when the plug gets old and requires a bit more voltage to fire, the problem could come back.

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