Re: A lot of carbon on spark plugs. How to fix?

[rrgunslinger]

You can do two things, change your jets and or lower you needles.  Only do one at a time.  But before you do that put new plugs in your bike, find a three mile stretch of road and run the bike at 70mph or at 5-6000 rpm for 3 miles.  While still running shut the motor off and at the same time pull the clutch in.  Pull over and check the plugs (take a plug wrench with you).  If black change the jets to a smaller size.  If they are a light brown the jets are ok and I would lower the needles (on the ones that were bad) one notch at a time until you get a good tan spark plug.  

I am just now starting to go through the same thing.

On Thu, Jun 14, 2012 at 5:54 PM, Lucky 1 [via Honda CB750'S] <[hidden email]> wrote:

I cannot help you without all the important information.

YEAR/Size?
Exhaust type and muffler?
Intake system?
Slide needle position?
Main Jets?
Slow Jets?
Mixture screws?

I do not need any other info but carbs is the last thing in the tuning process.
So if the floats are not adjusted, valves are not adjusted, timing not correct,
you are not ready to work on the carbs.

1978 CB750K Completely restored cafe style

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[Re-run]

Well there ARE more things you can check.
It is usually something intake related but not always.
Dirty air filter
choke stuck
retarded timing
bad plugs
bad plug boots or wires
jets too big or dirty(yes dirty, if the idle jet is plugged, it pulls on the mains. I had this on #2 a number of years ago.
Air/fuel screw incorrectly tuned
These are all possible issues.

[rrgunslinger]

good point