[1 Thump]

I went up a couple of jet sizes on my electra. She runs better than ever. But, the plug has a coating of black soot on it. Is it bad. I hear it runs cooler when rich, but can something bad come out of it ?

[zentrax]

Nothing bad will happen in the short term, you will be using bit more fuel than needed, but you could carbon things in combustion chamber up quicker than normal. Unless you have done some big mods to motor, going up 1 jet size at a time and testing is plenty. Find correct mainjet size first, then work down to needle height, then pilot jet. Test mainjet by using at least 3/4 throttle on traveling up a slight gradient, then cut the motor with kill switch but keep throttle in same place when you do. After, remove plug and inspect, best is tan colour but a slight bit of black is ok, these motors do like things a fraction on the rich side. I installed a brand new 33mm flat slide mikuni designed for a DR 350 suzuki dirt bike so had to jet completely from scratch, ended up using different needle and all.......but well worth it.......TORQUE HEAVEN!.......and a boost of power

[singhg5]

It will be difficult to start if electrode gets carbon deposits.  May need to replace spark plug more frequently.

[PhilJ]

If your completely stock there was probably no need to re-jet. Do you still have the CV carb? If so the stock jet is 110, maybe going to 112.5 would make it a little more responsive on the big end roll on. If exhaust mods have been done then a 120 may work or even a 125 . Sooty, as said, in itself wont do great damage, but it's not the bests thing either.

Edit: Oops, I thought I was in the AVL section, so what I said was based on that presumption, but the premise is the same.

[1 Thump]

I have a KnN filter and shorty straight through exhaust.

[PhilJ]

Re-read the edit on my earlier post. I edited while you were posting.

[UncleErnie]

I'm not much with carbs, but could this be alleviated to any degree by playing with the mixture screw?

[boggy]

I had the same thing when I bought mine with a few thousand miles on it.

Wouldn't start.  Pulled plug.  Sooty as all hell.  I was running too rich.  Dialed the mixture screw to lean it out a touch (I think I did 1/4 turn at a time based on recommendations from here). 

A whole riding season later I'm soot free.

[clamp]

Main jet or metering jet controls the max amount that can flow through the carb at 3/4 to full. You dont need to look at plugs on a single if it runs better if you back off from full throttle then the main is small but hell how often do you do that.
   The idl jet  runs the bike up to 1/4 throttle as the needle jet is slowly fed into the system as the slide opens more.

     Your needle adjustment will compensate for your mods