[Eagle56]

Hi

The electric is missing on normal revs and clears at full revs pulled the plug and it is black showing a very rich mixture

Any suggestions why

[Arizoni]

I don't recall which RE you have and the answer to that question has a lot to do with the suggestions we can give.

For instance, a lot of our members living in India have a carburetor on their UCE powered motorcycles.  Others world wide have fuel injection.

My first suggestion would be to tell you to remove and examine the paper air filter.

If it is dirty or it has any oil on it, that could explain your fouled spark plug.

My second suggestion would be to change the spark plug(s) and see if that doesn't temporary cure the problem.  (This is temporary because doing only this doesn't solve whatever is causing the black carbon accumulations.)

[Eagle56]

It's an Electra efi 2009 no oil just black plugs
Looked at the airfilter which still looks like new.

Misses so much it nearly cuts out.

Ordered a new plug the one I put in which ran fine to up to now was a triple contact type

[Vince]

     The negative battery cable end tends to break, but is held sort-of-together by the rubber cover. There is just enough continuity to run, but not enough electricity to run well. The engine will pull poorly and/or erratically, and foul plugs.
     Those fancy plugs are best at making you feel good about spending extra money. Use NGK BPR6ES. They are cheap and they work fine. If that isn't working then you need to fix the actual problem with the bike.

[Eagle56]

I will check e battery earth tomorrow

What is strange to me is when I open the throttle wide open it pulls without and missing

[NorEaster]

1st thoughts... check the negative battery wire and check and possibly change the plug.
Many recommend to change from the OEM Bosch to a NGK; and I did initially but got better performance on my 2014 C5 with the Bosch.

[Ducati Scotty]

If it's not the battery terminal, check that the throttle body and manifold are not loose and that there are not vacuum leaks.  If they are loose or a gasket is damaged, it can let in too much air and cause the mixture to be off.  But I'd bet it's the battery terminal.

[Eagle56]

Battery connections are good changed the plug and it seems better (NKG) but need to ride it more to really test it

Thanx

[Vince]

     It's not the battery connections, but the cable end that causes the problem. They tend to break in the rubber cover, then the cover holds them so the broken ends make some kind of poor connection.
      Also, FI systems have a start default mode. For about a minute after any start up it will run rich, even when warm. If you are taking a lot of short runs you may foul the plug, as the engine is not getting warm enough to burn off the excess rich mixture.

[Eagle56]

The ends look good as far as I can see by removing the battery

What happens if I've started it before the system checks have been completed

[Arizoni]

The lead battery terminals and the steel/copper connectors attached to them are not the possible problem.

When folks say "Battery Cable" or "cable ends" people think the steel/copper connecting terminals that are attached to the lead battery terminals are the thing that is being suggested.  They, and their connection to the lead battery terminals are NOT what people are talking about.

The Negative battery cable assembly actually consists of two wires attached to the steel/copper connector.  One heavy or thick one and one thin wire. 

The heavy wire that is connected to the steel/copper connector carries the ground or negative power to the frame or starter motor. 
This wire seldom causes a problem.

The light weight wire is also connected to the steel/copper connector and it is this wire that causes the problem.  This is the wire that grounds all of the other electrical things on the motorcycle and if it is broken or disconnected, all of the electrical parts may work sometimes and not at other times.

There is a rubber sheath that covers up the area where both the heavy and the light wire are attached.

This rubber sheath holds the wires "almost" together if one of them breaks.
That makes them sometimes work and sometimes not.

Because the sheath covers up the area, it must be split and removed to see if the small (light) wire has broken inside of it.

Splitting and removing the cover is the only way to really check out the condition of the thin wire.  Just pulling on it won't do because sometimes the wires insulation tends to keep the wire ends on both sides of the break together.  (That's why it sometimes works and sometimes doesn't).

[Eagle56]

Brilliant explanation, now I know where to check

Thanks

[Vince]

     Good job, Arizoni.
     Eagle, When you turn the key on listen for the fuel pump. When it stops spooling up the bike is ready to go. It just takes a few seconds.

[The Old Coot]

Here's the end of the cable terminal on my C5 yes it was tight but after I pull the c over back it more or less just fell apart.

[mattsz]

What those guys said.  Only - just to be clear...

The heavy wire that is connected to the steel/copper connector carries the ground or negative power to the frame or starter motor. 
This wire seldom causes a problem.

The light weight wire is also connected to the steel/copper connector and it is this wire that causes the problem.

...for me - it was neither wire, but the metal terminal end that caused the problem - twice! - into which both wires were crimped.  So while it may be the interruption of current flow in the smaller wire that caused the problem, the connector itself broke, not the wires.  I had to strip the heat-shrink insulation away to find it - here: