Hello,

I recently purchased a MC21 here in the US. Everything was working good but now one cylinder is not working some how. I am new to working on motorcycle also.

The engine starts and runs. If i am sitting on the bike the pipe next to my right feet does not get hot. That is the side that is not running. I see one spark plug behind the front tire and I took that out and inspect it and it felt little warm so I am guessing that one is the Ok one. The other spark plug seem to be under the tank I am not sure if the tank need to be removed to get to it?? DO I need to drain the gas first to remove the tank?? Never done it before.

Any quick easy fix?? thanks.
Also I am also wondering what model I have?? Wet or dry clutch?
I will post picuture later

thanks.
Jim

Yes, you will have to remove the tank to get at the other spark plug. Make sure you first put the fuel petcock in the "off" (horizontal) position to stop fuel flow. When you lift the tank at bit, you'll need to disconnect the fuel line from the petcock before you can lift it completely off. The line likely will have a spring clip of some kind holding the rubber fuel line tight on the metal part of the petcock. Push that off before trying to wiggle the fuel line off - may need to use a flat blade screwdriver to lever the line off. Good luck with it - once you've done it once it will seem easy enough.
_________________
-Jim
'93 MC21

The right pipe runs to the cylinder that points at the front wheel - the spark plug you removed. It may have been getting warm through conduction of heat from the other cylinder.

Remove that forward plug again, and plug the lead back onto it. Rest the metal portion against the metal of the engine, and have someone crank over the enigne (with ignition on and kill switch set to run) while you watch for a spark.

Come back and tell us what you found.
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MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Thanks for the replay actually I checked for spark at the front spark plug already last night. I put a inductive timing light on the spark plug wire to check for spark but nothing so I was thinking no current coming and while the engine was running I pulled the wire off the spark plug and the tic tic spark jump was there and going strong so that lead me to believe the coil and wire is good but maybe the spark plug or cylinder it self??

Ah right, in that case, either fit new a new plug, or swap them over and see what happens.

What colour is the electrode on the suspect plug?
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

I did some reading and it's looks this color is the R model with wet clutch??

Admin Edit: Images must be hosted on a public server!

That's very nice Norcal, but what colour is the end of the sparkplug!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

I took the lower spark plug out and it is black. I didn't have a replacement so I used a car spark plug to tried it. I can't really tell if the cylinder is running or not with the car spark plug but the exhaust is little warm but left side is much hotter. With the OEM NGK the RPM is ~1400 with the car plug the rpm is ~2000 so I guess the cylinder is somewhat running ??

I just got two new plugs from the local part store and will be trying it again tomorrow, thanks.

You're brave! The wrong plugs won't help much, and may damage things, but it seems you got lucky.

Anyway. The plug is black because it is not fully burning the mixture, which can be for a variety of reasons: Weak spark, poor timing, poor caruration to name a few.

Sometimes, if the cylinder doesn't fire up straight away, the misture wets the plug and shorts out the spark. When this happens there's not much you can do but remove and clean / dry the plug and try again. Better still fit new plugs.

Let us know how you get on!
_________________
MC21SP Plaything
BMW F800GS Bumblebee
Triumph 9551 Daytona Big boys toy
FJ1100 Sporting relic
GTS1000 oddball

Ok so I put the new correct spark plug in and the cylinder seem to be running now but it runs not as well as the left side.

The right pipe is not as hot and the left.
Lots of black spots of the right none of the left
Right side pop pop pop a little.

Seems to be too rich on this side??

thanks.

Ah, let me jump in with my old favorite....check your coil connections! Make sure it is very clean, no sign of arcing, and a good tight connection. Mine was not, and it did the popping thing, fouled a plug, went cold, and quite generally drove me mad until I figured it out. I still haven't recovered completely, some would say, even though the bike has. If the connection is iffy, just change the female connectors. Good luck.
_________________
-Jim
'93 MC21

pop pop pop lol sounds like a ign feed or coil breaking down.
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If I have to take the carbs off once more...

Now I open up the side cover so I can see in there.
The right side is running now but something is weird I hear tic tic tic somewhere like spark arcing. If I remove one connection from the coil then the right side goes quite and tic tic tic is gone.

It sounds like a spark leak but I look everywhere and nothing. Normally with this loud of tic I should see the arc or feel it lol.

Just can't locate where the tic is maybe engine internal?? but with the right coil disable the tic is gone.

The right exhaust is still rich like and pop pop little pop.

I tried the coil connections and they are very very snag. Getting them on and off takes little force.

So what now?? I have no coil to try so???

If it's arcing you should see some evidence of it on the coil blades I would think - burnt look, pitting, etc. In any event, you can try swapping the coils with each other and see if the problem switches cylinders. You basically want to rule out the coil itself versus the connections.
Does "snag" mean loose? If so, you can try gently pinching the female connectors together with needle nose pliers to try to get a firmer connection (if it were only so easy with human females, but I digress!). If this gets rid of the problem, I would view it as a temporary fix and suggest you go to Radio Shack or some such place and get a couple of female connectors and replace them. If you rule out the connections, there are tests of the coils themselves that can be done if you have a volt meter, though I'd have to dig through old notes to be able to tell what the readings should be. Others probably know from actual knowledge.
_________________
-Jim
'93 MC21

coil readings using a multimeter should be:

Primary resistance - 0.1~0.3 Ohm
Secondary (no cap) - 2~4K Ohm
Secondary (cap) - 5~11K Ohm

thanks to Matt@tyga for info from a reply to my earlier post.