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Motocarb started fitting UFO inserts to VM Series competition carburettors in 2014.
​Our UFO equipped carbs have been quietly providing more power over non UFO carbs in many competition classes.
These inserts are proven to work in both 2 and 4 stroke applications.
Popular fitments include
Matchless G50, Manx, Yamaha & Honda 500 singles (VM38 & VM44) Aermacchi 350 race, Ducati 250
Yamaha TZ350 (VM38 power jet) 
We've supplied carbs fitted with inserts for numerous other makes and models.


"Got it yesterday. Just had it running Fired up first bump. Runs fantastic. Many thanks. Again I’m delighted "
Malcolm.  Georgia USA    Aermacchi 350 race


When installing UFOs, the pilot jet must be reduced substantially (usually about 50%, sometimes even more).
The UFO is a simple, trouble free, aerodynamic piece that fits VM Mikuni carburetors from 30 mm through 44 mm. The UFO makes a normal round slide carburetor out-perform the more expensive flat slide carburetor by eliminating turbulence and increasing air flow and velocity, creating a highly atomized fuel charge. Normal gains are 3/4 to 1 HP per 100 cc of engine displacement on 4 stroke engines and 1 1/2 to 2 HP per 100cc of engine displacement on 2 stroke engines. (Minimal rejetting and tuning are required).
  • More horsepower with less fuel
  • Broader power band
  • Explosive throttle response
  • Superior fuel atomization
  • Less sensitive to temperature, altitude and jetting changes
  • Cleaner emissions
  • Cooler running engine
  • Easier starting and warm-ups
  • Eliminates cold pipe syndrome
  • Works great with stock or modified engines
    ​
We recommend that you let us fit the insert to your carburettor as there is some machining required to the throttle valve and the carb body, as well as setting up the carb to work correctly with the insert. You should call Steve on 0151 924 5383 to discuss the work.
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Without the U.F.O., the air hits the forward wall of the slide cavity creating a rolling air turbulence which forces the poorly atomized fuel droplets to the lower portion of the carb bore resulting in poor fuel atomization and poor performance.

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​With the aerodynamic U.F.O. filling the slide cavity, the rolling air turbulence is eliminated. The higher velocity air flow pulls the fuel further up the needle and higher in the carburetor bore resulting in superior fuel atomization. This means more HP, quicker throttle response, improved fuel economy and a cooler running engine.

We have inserts in stock to fit
VM26-VM28
(RD250/RD350 with 24mm ID throttle valve)
VM30, VM32, VM34, VM36, VM38, VM40, VM44
​To order, call Motocarb on 0151 924 5383
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