The VM38-21 is supplied with the following factory jetting installed:
Pilot jet 40 (VM22/210), Needle 6DH3, Needle Jet Q-0 (166 Series), Main Jet 360 (4/042), Air Jet 2.5, Slide Cutaway 2.5 (VM38/24), Needle valve 1.5 (VM28/163 for fuel pump supply)
Dimension A= 43mm, B= 116mm, C= 154mm, D= 62mm, Total Width 79mm
Unlike many motorcycle manufacturers’ purpose modified versions, these factory VM Round Slides are both 2 and 4 stroke compatible and are regarded by the factory to be the best performing version of this carburetor ever made.
These are the most popular high performance singles carburetors in the sport of motorcycling. Mikuni’s VM Series round slide single carburetors have proven themselves as the performance standard for use in any single cylinder motorcycle and ATV applications for motocross, enduro and trail riding, to flat track racing and road racing on both 2-stroke and 4-stroke engines.
Performance features for the VM Series Carburetors include a large selection of bore sizes for increased fuel mixture flow to match engine modifications. And the VM Series offers a wide range of tuning components to allow precise fuel mixture metering in any application, at any throttle setting, under any riding conditions.
Tuner jet kits can be purchased separately for many different motorcycles as per the corresponding options. These kits consist of the suggested jets for changing that are not matching those factory fitted in the VM38-21, they include an extra one size up and one size down main jet for tuning the main circuit due to fuel quality variations, altitude and climate. Testing and conformation of correct main circuit jetting can only be done by physically changing jets and WOT testing.
These tuner jet sets have been determined from thirty years of experience, customer feedback, plus research and development as the Australian Mikuni distributor. From time to time these may not be exactly right for every engine, usually due to changes to porting, compression or numerous other things that contribute to the requirement for additional fine tuning but as a rule our kits are spot on or a very close and useful starting point, but we give no guarantees and sorry do not release kit details or jet size information. If you have your own spec simply purchase the carb and buy any other required jets from the jet pages. This also applies to replacing jets in other VM38’s as the 166 series needle jet and others items may not match and fit.
Keep in mind that these are suggested specs, and all tuning procedures, as found in our Tuning Tips section must be adhered to for the confirmation of any supplied jet’s compatibility with your engine.
(The picture with the cable shows the required length of inner cable protrusion and securing fitting at the carb end on basically a minimum length adjustment. The back board is divided into 1 and 10mm increments)
All international buyers are responsible for the payment of their domestic customs duties and taxes charged on imported goods. The duty free threshold and duty/taxes payable rates differ from one country to another and we strongly advise you check your liability before ordering if unsure. Please check your tracking on all international shipments within 7 days to follow their progress and determine if it is being held by your local customs dept. or on their behalf by the Postal Service, who you will need to make contact with using the provided tracking number.
Please Note: Other than exact replacement OEM carburetors, all Mikuni Aftermarket Carburetors and Tuning Components are sold “As Is” for Off Road / Racing Use Only and are not intended or approved for use on vehicles operated on Public Roads or in locations where applicable engine tampering and anti-pollution laws apply.