Mikuni carbs

[SuzukiGS750EZ]

my 82 suzu gs750e has mikuni carbs on it and i believe its running rich. I say this because the plugs are pure black even after i clean em off and gray smoke comes out the pipes until i get it idling around 1000 rpm or so. My question is, is this something i should adjust or just leave? And if so, i saw the carb cleaning section on the resources homepage but i didnt see anything in there about adjusting them. They are squeaky clean if that helps any.

[chef1366]

How's your air filter? It will run rich with a REALLY dirty filter.
You've had these carbs apart and know for sure the internals are "squeaky clean"
If you have a bad battery and a weak spark it can create black plugs.

[Quasi]

Are they squeaky clean on the inside though?





Carbs are my favourite, spent many hours on them with mixed results. Mikuni are still the best in my opinion for reliability, many other carbs require frequent set up.

I may be repeating something that many of you know anyway but the basic error most people make with carbs are they don't realise that there are three sections to a carbs internal workings which perform right through the rev range of the motor they are attached to.

Many initial problems are with the starter circuit which have the smallest holes whilst not being very accessible either. You can generally smell if the bike is runnng rich by a strong smell of unburnt fuel emitting from the exhaust. The started circuit of a standard carb cannot be adjusted the slow circuit and main circuit can be, the starter circuit is fed by a fixed pilot jet and a fixed air jet which has been predetermined by the factory to supply the necessary amount for the engine to idle without the need for an open throttle.

I could bang on about this, but Im generalising here so don't shoot me if you disagree with what I have said, but you have to be confident that you have a clear starter circuit, by that I mean you have unblocked every necessary hole some of which you cannot see but carb cleaner will penetrate.




Quasi.

[SuzukiGS750EZ]

Well my grandfather is a mechanic, has been for a looooooong time. So i trust that he had cleaned the carbs thoroughly. My bike doesnt smelle when running, it just puts out a grayish white smoke. It pops sometimes too, not loud but if your behind it while its warming up you can hear it. The battery is brand new, the air filter is brand new and so is the oil. I checked the gap on the plugs and they are all the same. When it idles around 1000rpm or i rev it up it doesnt put out smoke anymore. Its not like a big cloud of it, it just comes out of the pipes for six inches or so and dissapears.

[mcan]

Are one or more of your float needles leaking? I had poor mileage and rich running and one of the other riders in the group noticed a strong fuel smell when following my bike. I did a "bench" test by attaching clear fuel hoses to the carburetor fuel inlets and then filling the lines with fuel and observing if the level went down. Sure enough, I was losing fuel through the float needles and into the carb throats. Not a major amount but the throats were always damp. I never saw any dripping from the vents but the curving of the tubes made them higher than the carb bores.