It doenst happen often just so happens i went through a small town that was having election day yesterday. i didnt really want to make to much of a racket.
there is some soot in the exhaust and the plugs are darker then they should, i had them out while doing the cams. Honestly i dont know much about carbs or bikes for that matter thats why im here. To learn
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On the 42 mikuni there is a BIG brass plug on bottom of float-carb. to remove..... GAS WILL COME OUT when you remove it..... the MAIN JET sits there in plain view.....
Straight bladed screwdriver to CAREFULLY remove it and with YOUNG EYES,,,, A MUST,,,, you should be able to see the size of that jet..... LOOK at the SCREW DRIVER SLOT END on jet.. size stamped there....
the carbs usually use come with a 155 installed, mine did.... a .150/.155/.160/ and bigger can be had...
If your jet is a .155 or .160 you need to go to a .150 or .155 respectfully... IF IT was RUNNING RICH... usually 5 represents .005 thousands of a inch... and .005 will change the fuel mix a lot..
There is a SLOW SPEED up and behind the MAIN JET and for now I would leave it alone... it comes in .0025 increments and is located in a tunnel and takes a very small screw driver to take it out.... I have found the one it comes with to be close enough and by setting IDLE MIXTURE as described will prove it to be the right size OR NOT.....
the IDLE AIR ADJUSTMENT is in plain view toward rear side on mikuni... DON't TIGHTEN DOWN on it hard but .... CLOSE IT then GIVE IT 2 FULL TURNS OPEN.... START BIKE after bike is warmed WARMED means HOT from a RIDE not just sitting and idled to a warm condition..
turn the screw in to listen if it raises the RPM a little or OUT to raise and smooth out the idle.... THAT KNOB on the flex cable is JUST TO SET engine SPEED at idle... NOTHING to do with FUEL MIXTURE just IDLE RPM adjustment. 1000 to 1200 RPM is needed by most HD's and TOO slow at 950
IF YOU LUG THE BIKE AS SLOW AS YOU Said YOU WERE IN 3RD GEAR ..... THAT being the problem..... HARLEYS need to be RUN at NO LESS in these gears, but more if wanted.
1st= up to 25
2ond= 25 to 35 no less
3rd= 30 to 45 no less
4th= 40 to 60 no less
5th 55 to---- no less
6th NOT UNDER 60.....
THIS IS A MUST lugging under these speeds in the gears LISTED will DO HARM TO ENGINE!
the MIKUNI tuning book will show you all that I talked and then some.. good to download...
signed....BUBBIE