In Stock – Item is in stock
Usually ships in 2-4 business days – Item will be shipped out by ourselves in 2-4 business days subject to availability with our suppliers.
Usually ships in 5-10 business days – Item will be shipped out by ourselves in 5-10 business days subject to availability with our suppliers.
Made To Order – Item will be shipped out as soon as it has been manufactured and arrives in our warehouse. For a more accurate lead time, we would recommend that you enquire before placing an order.
Out of Stock – Item is currently out of stock. Availability will update when item becomes available again.×
Mikuni's Research and Development Department has spent many months to improve the HS carburetor series to meet all the street riders performance needs. First step was a larger body to fill the need for bigger throttle bores in all-out performance applications; step two had to be a smoother and easier throttle operation. This resulted in the design of the HSR42 carburetor. A major feature of the HSR42 is the flat throttle slide assembly with roller bearings. Unlike butterfly throttle valves, which obstruct the carburetor's venturi at all throttle openings, creating airflow turbulence and hindering precise air/fuel metering, the flat throttle slide allows an unobstructed venturi at full throttle, thus flowing more air and carbureting more precisely at all throttle settings. The roller bearings on throttle slide provide a light throttle action, which offers smoother control and allows the use of a very light throttle-return spring. With its 42mm venturi, the HSR42 flows 20% more air than the HS40, making the HSR42 an ideal carburetor for Evolution Big Twin and Twin Cam engines employing other performance modifications such as big bore kits, cams, pistons and an exhaust system (Mikuni still recommends the smaller HS40 carburetor for stock and mild tuned Evolution Sportsters).
Flow bench tests by Jerry Branch show that the HSR42 Mikuni, while still being smaller in venturi size to some other popular carburetors, is able to flow more air to the engine once installed on the manifold and head. The HSR42 Mikuni actually flows more air at full throttle to produce more peak power. At partial throttle openings, the Mikuni's smaller, yet higher velocity flowing venturi, together with its advanced fuel-metering system provides a stronger overall powerband with improved ridability. Other performance features of the HSR42 include a larger capacity float bowl and a higher flowing needle-valve assembly to accommodate extended full throttle operation.
Also, more positive action of the high leverage float valve prevents the possibility of the float bowl over filling or the needle-valve flooding. This eliminates the need for overflow and vent tubes on the carburetor body, giving the carburetor a cleaner look. An adjustable accelerator pump provides instant throttle response throughout the RPM range. Kits work with 1990-2006 style Big Twin throttle and idle cables. Other features are instant engine response, improved rider throttle control, more mid range power for faster acceleration and passing with more confidence, good gas mileage and years of dependable service. Installation instructions and hardware are included with each kit. Mikuni developed several kits for special applications as well as "Easy Kits" that use stock manifolds, choke cable, air cleaner and throttle cable.
Total Kit for Evolution Big Twin Models 1984-1999 includes performance intake manifold, rubber mounting flange, HSR42 carburetor, high flow K&N filter, Chrome air cleaner cover, breather kit and hardware. Uses stock style 1990-1995 Big Twin throttle and idle cables.
Total Kit for Twin Cam models 1999-2006 includes performance intake manifold, rubber mounting flange, HSR42 carburetor, high flow K&N filter, Chrome air cleaner cover, breather kit and hardware. Uses stock throttle and idle cables.
Note: 1993-1999 Big Twin Models will need headvent breather kit (ARM010785)
Note: 1984 thru 1989 models also need 1990-1995 stock Big-Twin style throttle and idle cables.
All orders are shipped out of our warehouse with one of our trusted couriers. Our couriers include DPD, Fedex, UPS, DHL and Royal Mail. The courier used to ship your order is determined by ourselves once your order has been placed and normally depends on the size, volume and the shipping destination.
The selected courier for your order will be quoted in your order confirmation email which you will receive once we have processed your order. Once your order has been shipped, this will be confirmed via email and you will receive a tracking number so you can keep an eye on your shipments progress.
All courier services used are express services to ensure you receive your order in a decent time frame from the date of your order being shipped. (UK addresses are normally 1-2 days transit time).
Items that are labelled as 'In Stock' are shipped within 1 working day. We will do our up most to ship 'In Stock' item/s out same working day providing the order is placed before 2pm (UK time).
All other items labelled with different lead times are dependent on stock levels with our suppliers. If there is a problem with availability once you have placed an order we will contact you asap. If you wish to check availability on item/s before placing an order feel free to use our Contact Us page.
Any item that is labelled 'Made to Order' will be shipped out as soon as it has been manufactured and arrives in our warehouse. For a more accurate lead time on 'Made to Order' items, we would recommend that you enquire before placing an order.
Please note that if you order more than one item, your order will only be shipped once all items are ready to be shipped together. We can partially ship orders if requested but please be aware we may need to charge more for shipping.