Cylinder balance

I have a MK III Commando Roadster. I am running a Boyer ignition and it is converted to a single Mikuni carb.

I seem to have a consistent problem with the left side spark plug seems to be running rich and carboning up the plug. The right side looks okay, but the left get covered with black soot very quickly.

Someone recently told me that could be corrected with valve adjustment, but that doesn't seem right to me.

Any comments?

Valve adjustment can do the trick.

I would suspect oil consumption on that side. Does the exhaust smoke out one pipe?

I don't see any smoke on startup or while running. It has been my experience that rich on fuel deposits a sooty carbon on the plug, where oil will be a little more shiny. I have checked compression and it is well balanced between the cylinders. I put a small quantity of oil in the cylinder and there was no appreciable change in compression. I have also not noticed any appreciable loss of oil in the tank that would indicate it was burning oil.

The thought of valve adjust interests me before I start ripping things apart, since I have never thought of that angle. Could the carbon indicate to loose or to tight on that side?

By the way, thanks for all the input both on this question and in the past, this is the best forum I have ever been on.

Try removing the plugs and bring the pistons to TDC. Using a torch see what crud is on top of the pistons, it should be dry and light brownish, you could carefully scrape a little off to get a better look. Next rotate the crank until an inlet valve comes into view, they should be dry.

Cash

I had the same issue on ly the right cylinder. however, this is before I synced up the carbs. I'm hoping after it's back together that the carb synchronization will get them both running at the same level of hotness etc......

we'll know by the end of the weekend 8) and I'll report back

kfh

If your valves have proper clearance, do a compression test, if that turns up a differential of less than 10% try a new plug in that hole, if that doesn't change the situation try swapping the coils and see if the problem migrates. You have stated that oil consumption isn't an issue, my gut says ignition, old connections cause high resistance, do check every connection by pulling the connector and re-making the circuit. If the Boyer is old consider a new unit, or better yet a TriSpark or Pazon.

Lastly, you didn't say how you run the Norton, it is a sports motor and needs to be flogged (gently) every time you ride and it needs to be run long enough to stablize in its normal operating tempature range; a bunch of trips to the local post office will do more harm than good.

RS

Hey - Thanks for all the in put :lol:

When I ran the compression check the two cylinders were pretty equal as I racall. As for my riding style - I am not afraid to put the spurs to it at the proper time.

I am not sure how old the Boyer ignition is, as it was on the bike when I purchased it. I have entertained the idea of a coil problem. I ordered up a new Dyna coil, plug wires and caps yesterday. I thought I would start with ignition.

The entire wiring loom is new (for the second time - I let all the smoke out of the first loom I bought) :roll: This plug fowling has been a consistant problem since I bought last August. If this doesn't help, I'll consider a new ignition to replace the Boyer. I know it is like which car do you like, but which is the better ignition system?

Thanks again for the help

I thought I would give a brief update on the fouled plug problem. I decided I would eliminate other possible sources before I started playing with things like altering the valve adjust.

Since I did not know the age or condition of the ignition system, I elected to replace the two coils with a single Dyna 5 ohm coil and new plug wires. This seems to have stopped the fouled plug. I made a combo street/freeway run today. The plugs are now almost to clean. They are both pure white. Looking at the gold the new head pipes are starting to turn, it might be time to adjust the needle valve on the Mikuni and richen it up a bit.

Thanks for all the input. I post again if something changes.

did you ever replace the twin wire that runs from the ignition pick up to the coil,although they look and seem good the copper wire turns to crap at the corner were it goes through the case.I run the same set up on my bike,one kick starting,good mid range,clean plugs,even idle,the pipes run gunmetal blue down to the second bend, my only complaint is it runs out of steam at about 100mph,fit the cable choke set up it alot nicer to use.