Install Mikuni Carb On Sportster
Article by Mark Trotta
The Mikuni slide carburetor is a popular replacement for Harley Sportsters, but they are not a direct fit. Throttle cables, intake manifolds, and air cleaners need to be taken into consideration.
Flange Adapter
Mounting the carb to a stock Sportster manifold requires a flange adapter.
This adapter works with either 36mm or 38mm Mikuni slide carbs.
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If you're switching from a Bendix, Tillotson, or Keihin, you'll need the adapter, plus a throttle cable and new air cleaner. And you may need to replace or modify the right-hand grip as well.
Throttle Cable Hook-Up
Mikuni VM carbs require a specific throttle cable.
The carburetor end has a small ball on it, which fits into the top of the carburetor.
Single vs Double Throttle Cable
Starting in 1981, Sportsters were fitted with a double accelerator cable (one push, one pull). This was to help prevent accidental throttle sticking.
The Super E carb that was on this bike previously had a dual cable throttle, but a Mikuni slide carb doesn't.
I tried to remove one of the cables from the handlebar grip and run the Mikuni cable, but the 'push' and 'pull' ends on the throttle barrel have two different thread sizes.
For demonstration purposes, I threaded a 1/4" bolt on the 'push' side, and a 5/16" bolt on the 'pull' side.
The 'pull' side is the one needed for a single throttle cable.
The cable supplied had a 1/4" threaded rod, so I installed a Heli-coil insert on the 5/16" side, which reduced it to 1/4".
Choke Lever
Mounted on top of carb and inward towards the motor, the choke control may be a little awkward for some. Push down the choke lever for on, and after warm-up period pull up for off.
Air Filter Choices
A popular air filter for the Mikuni VM is the K&N RC-0850.
With the new carb mounted, the bike fired right up! Since then, the carb has provided easy starting and gives excellent street power for this old Sportster.
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Notes and Misc
When installing a Sportster intake manifold, there's no need to squash the life out of the two rubber intake gaskets.
Tightening the intake clamps with a nut driver will help eliminate over-tightening.
If switching from an S&S carb, you'll need a stock intake manifold, carb adapter, throttle cable, and air cleaner. A Super E is really too large for a stock Sportster motor anyway. The Mikuni will give nearly as much power at about half the price of a new S&S.
Shop: Mikuni VM Carburetor
The Mikuni Corporation is a Japanese manufacturer of automotive and motorcycle related parts and equipment. They offer several other styles of carbs, but the VM series is their single most popular performance carburetor.
If needed, replacement parts and overhaul kits may be purchased from Sudco International.
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