My MC21 dint idle, then i notice that the lower cylinder doesn't fire. checked . What i did i reduced the spark gap from .7 to .4 and then it fires, is there i case that my coil is weak?

I guess reducing the gap will make the current more powerful?

rgrds
Demetris

http://www.ngkntk.co.uk/technicaltips/sparkpluggap.asp
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Andy.
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THanks Andy

thought was the opposite situation. Except of that is it possible is the coil fault because the cylinder doesnt run with the normal gap.

Not my field I'm afraid, but I would consider replacing the coil and plug cap.

Make sure all the connections between the PGM-III and the coil are clean and tight too. Put a multi meter between the pin on the PGM-III plug and corresponding connector on the coil. I don't know what it should roughly read, but there are some guys with electronics experience here who will probably have an idea.

Maybe if you test all 4 coil connections and post the resistance readings for each, someone can spot something?
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Andy.
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Guys

after 10 months of mess, cleaning carbs, replacing things, the problems with lower cylinder where solved with the coils.

So anyone has the same problems please save that 10 months by replacing the coils

sounds like good advice

have a look at my query posted yesterday. guess replacing the oem part after twenty years might be the first thing to think of.

have you found a good place/price for your coils and are you buying two.

thanks

My god thought i was messing long time with it.

I went throught most of the electrics, carbs, PGM's and i ended up on coils, that was the last thing to look, i gues should be the first

Got them direct from Japan, 35 each.

Try checking the coil spade end connectors before actually replacing the coils.

The vibes can make these go loose, which causes arcing and then you drop a cylinder.

You can spend ages running around, swapping plugs and components, when all you needed was a quick squeeze with some pliers.

The first time I had this problem I spent the time looking for bigger problems first. The next time I had the same problem on another bike, the first thing I checked for (and found) was a dodgy connection.

Might not be this but can save you a few quid.