UPDATE : Boyesen is in the process of a website upgrade. Until our new store is up and operating, please use a local dealer or
online retailer to make your purchase. We apologize for this inconvenience and will have web sales back as soon as we are able.

Boyesen Engineering

Skip to Main Content »

Search Site
Back to V-Twin Home

The Boyesen TWIN SHOT CV40 KIT converts all OEM HD CV-40 carburetors from 1992-2006 to a standardized fuel delivery system. By installing the Boyesen TWIN SHOT KIT, all model year HD CV-40 carbs can take advantage of the range of benefits.

» Standardized Fuel System for Application Simplicity
» Precision Twin Hole Sprayer for Improved Roll-On Acceleration
» Patented QuickShot Accelerator pump technology Eliminates Low Speed Bogging and Coughing
» Adjustable Fuel Jet to Control Accelerator Pump Fuel Spray
» Dual Check Valve System for Consistent Spray Pressure
» Removable Sprayer Allows Convenient Service and Maintenance
» Removable Main Jet Cap for Easy Access Tuning
» Precision Accelerator Pump Plunger Rod Improves Spray Response
» Stiffer Spring on Activation Arm Delivers Consistent Spray Response
» Available in Polished Aluminum or Matte Black finish
» Bolt-On, No Modifications Required. Includes New Float Bowl O-ring, New Plunger Arm and Plunger Arm Boot.

If you'd prefer to speak with a real live person, just call us at (800) 441-1177 to speak directly to our Customer Service specialists. Call our toll free order line (800) 441-1177, or e-mail us at info@boyesen.com

The Floatbowl Body: The Harley-Davidson OEM CV-40 carburetor floatbowl over the years has many different locations for fuel to enter the accelerator pump cover. The Boyesen TWINSHOT will convert all versions of HD CV-40 carbs from 1992-2006 to a standard "fuel-in" passage to the accelerator pump cover. By installing the Boyesen TWINSHOT, all HD CV-40 carburetors can take advantage of the benefits of the fuel delivery system.

Twin Hole Sprayer: Why a two hole sprayer? Two smaller holes create a finer spray with increased velocity, which will improve atomization of the fuel. The stock sprayer is pressed into position which makes it very difficult clean or replace when today's not-so-clean fuels clog it. TWINSHOT uses a removable design with a precise alignment socket to ensure proper spray angle for that important TWIN SHOT of fuel.

Dual Check Valve System: Most OEM CV-40 accelerator pump covers do not have a true check-valve system. TWINSHOT incorporates a new style ball and spring system that helps to eliminate fuel dirt from clogging the system. The second check-valve is located at the sprayer for a more immediate response of fuel spray when the throttle is turned.

Patented QuickShot Technology: The V-Twin QuickShot is the next generation in accelerator pump fuel delivery. The patented design accelerates fuel delivery while eliminating troublesome trapped air that can cause bog and hesitation. 25% more fuel capacity plus added bleed capability allows for solid fuel delivery 100% of the time. The QuickShot is equipped with an adjustable leak jet system.

Adjustable Leak Jet: All HD CV-40 carbs are basically the same regardless of motor size. Additionally they all have a fixed leak jet. The leak jet regulates the amount of fuel and the time duration that fuel is sprayed into the carb. The adjustable leak jet feature on the Boyesen TWINSHOT allows for the size of the leak jet to be adjusted so you can tune the fuel spray volume and duration needed for the size of the motor. Also, the carburetor being sensitive to temperature and altitude, the adjustable leak jet can be quickly tuned for changes in temperature and altitude.

So what exactly is a leak jet, how does it function and what is the importance of adjustability? A leak jet controls the volume of fuel and the duration of spray from the accelerator pump. All carburetors have circuits for different RPMs and throttle openings. The circuits jet sizes are determined by a variety of factors such as; ambient air temperature, altitude and specific gravity of the fuel. Jets and passage sizes are determined and fixed according to these factors. A fuel delivery problem exists in two general conditions. The first is the speed at which a throttle slide or butterfly is opened. A 4-stroke motor uses an accelerator pump to deliver an extra "squirt" of fuel to compensate for the influx of air entering the carburetor. As vacuum builds from the incoming air the low speed jet and needle circuit take over eliminating the need for accelerator pump assisted fuel delivery. The amount of fuel and the duration (length of time) of the fuel "squirt" must be timed perfectly for maximum acceleration performance to occur. The second condition is temperature. The low speed jet and main jet are fixed for the conditions, but if the temp changes, the accelerator "squirt" needs to change to compensate the transition from low speed jet to needle and or main jet. The TWINSHOT incorporates an adjustable leak jet accelerator pump cover (APC) to the accelerator pump system. If the ambient air becomes cooler, your bike will run leaner and you will need to richen the fuel "squirt" by turning the adjuster on the TWINSHOT's APC. By turning the adjuster "IN" you are making the leak jet smaller forcing more fuel into carburetor by lengthening the duration of the spray. This helps the transition of the low speed jet to the main jet circuit. The opposite conditions occur when the ambient air turns warmer. By turning the adjuster "OUT", the leak jet becomes larger allowing more fuel to leak back into the floatbowl. This reduces the duration of "squirt", which makes a leaner shot of fuel. The adjustable leak jet APC allows a rider to change the fuel "squirt" by making a small turn of an adjuster. Now you can be out on the road and tune without having to disassemble the floatbowl and change jets.

Stiffer Activation Spring: We found that the spring on the activation arm had a lag when the throttle was turned sharply. This lag prohibited the plunger arm from contacting the diaphragm, causing delay of fuel spray and contributing to the motor spit and sputter. Increasing the spring stiffness 5% ensures accurate reaction of the fuel delivery system when the throttle is turned sharply.

Accelerator Pump Plunger Rod: The stock accelerator pump plunger rod has had some inconsistencies in its length which effects the way it contacts the diaphragm. We have determined the ideal length for the most consistent fuel spray action.

Removable Main Jet Cap: When the season's change so should your main jet. On a stock HD CV-40 carburetor the floatbowl must be removed to change the main jet. The TWINSHOT has a removable main jet cap to access the main jet without taking the floatbowl off the carburetor. which makes main jet changes a snap.

Assembly of the TWINSHOT: The TWINSHOT is delivered pre-assembled for a true bolt-on product, no modifications required. The TWINSHOT consists of a floatbowl body, adjustable accelerator pump cover, diaphragm, diaphragm spring, activation arm, plunger arm and plunger arm boot.

The combined benefits incorperated into the Boyesen TWINSHOT kit creates a synergistic effect that will make the HD CV-40 carb respond as if the bike was fuel injected. The combination of the 5% stiffer activation arm spring and the precision plunger rod ensures that when the throttle is turned, the plunger rod acts upon the diaphragm. This forces fuel into the dual sprayer and squirts a twin shot of fuel directly into the bore of the carburetor. The effective twin shot eliminates hesitation and bogging.

I installed both the Power X-Wing and TwinShot at the same time, very easy to do, first class product to install. I originally gave these products a try because I believe in the stock CV carb. I have an '03 WG, stock 88, air filter, Vance & Hines jet kit, Krome Werks slip-ons and Screaming Eagle plugs. I will let you know this is the best mod i've done to any bike in some time. Easier starting...cold or warm. Made the throttle response much, much better and as far as riding, just an unbelievable change to a carbureted bike. This thing works awesome, definately carry a gear higher like advertised, no bucking or coughing in 5th geat at low RPMs. I can tell you it was money well spent, and it made my Harley run better than I thought a Harley could. Two thumbs up for sure! - V-Twin Forums July '11

I recently purchased your product called "TwinShot" for the carburetor on my 2003 Harley Davidson Dyna Wide Glide and I must say the product performs exactly as advertised and I am very pleased with it ...Twin Shot cured the sputter, backfire, burb, cough and hesitation I experienced when backing off and then geting back on the throttle .... the adjustable leak jet is simple and easy to use and an outstanding feature. Thank you! - Vincent V.

Installed your TwinShot today and am very happy with the results. My 1995 has a blower on it and needs that extra shot. Thanks for a product that works, now my motor runs from the start and doesn't quit on me when I'm ready to shift. I again am smiling after my ride - my worry now is to control it and not get any more tickets. THANKS AGAIN - James A.


Q: Will the TWINSHOT cure my bikes bog, cough and hesitation?
Q: What gains will I receive with twin shot?
Q: Will it fit my carb?
Q: What is an adjustable leak jet?
Q: What are the benefits of the adjustable leak jet?
Q: Will I need to retune or redyno my bike?
Q: Is it hard to install, can I do it myself?

Q: Will the TWINSHOT cure my bikes bog, cough and hesitation? A: Yes, in most cases. Unless you have other motor or carb problems that cause the issues. Q: What gains will I receive with twin shot?

A: Improved throttle response.

Q: Will it fit my carb?

A: The TWINSHOT will fit all stock Keihin CV-40 carbs from 1992 till 2006.

Q: What is an adjustable leak jet?

A: Adjustable leak jet is a needle that allows you to control your spray duration and volume from your accelerator pump circuit.

Q: What are the benefits of the adjustable leak jet?

A: It will allow you to tune the accelerator pump circuit for temp changes and elevation changes.

Q: Will I need to retune or redyno my bike?

A: No, The TwinShot will come pre-set for your carbs current settings. It will not require any rejetting of the pilot, needle, or main jet.

Q: Is it hard to install, can I do it myself?

A: It’s not hard at all, it takes a ½ hour to install with basic tools.



Search By Vehicle


My Cart

You have no items in your shopping cart.

Compare Products

You have no items to compare.

Keep your eyes open for our special Back to School items and save A LOT!