Allens Performance Ltd.

Allens Mikuni VM28-57 carburettor specially prepared with a custom made, radiused air entry

February 21st, 2020

For your viewing pleasure, a specially prepared, bespoke Allens Mikuni VM28-57 carburettor  with a custom made, radiused air entry.

A generous radius helps to guide air into the carburettor entry, massively reducing turbulence and allowing the pressure drop caused by the engine to draw more air than it otherwise could. Due to production practicalities the carb manufacturers rarely put a particularly nice shape on the rear of the carb. This can be rectified, but a new piece has to be made, pressed on, holes filled, then turned, shaped and blended in. A lot of lumps and bumps that disturb airflow have been removed. In this case, the air hole for the cold start fast idle has been blocked up and smoothed over. A little compromise in the name of high performance.

An extra difficulty with modifying this type of carburettor is that the inside diameter of the carb is not concentric with the outside. This means more metal is removed from the top than the bottom. It’s very tricky to make sure there is still enough metal left in order to avoid the whole thing falling apart.

The front spigot has also been modified to fit a rubber that the customer provided.


Mikuni VM28-57 carburettor with custom made radiussed air entry


A picture of the standard carb below is a great comparison:

Mikuni VM26-8639 Carburettor

New Moto Guzzi VM32 Carb Kit Available!

July 10th, 2018

Meet VM32-0407-K, Mikuni VM32’s for the big Guzzi Twins. Including Allens Performance specially cast and machined manifolds! Smoothest tickover ever.
Moto Guzzi Big Twin 1000G5 VM32 Mikuni Carb Carburettor Kit

26J Yamaha Mikuni TZ Reverse Slide Replica Carburettors Built to Order

January 26th, 2017

Fantastic! Finally it’s possible to get a close match for the reverse slide carburettors most sought after by TZ riders rather than put up with tired old orignals. Genuine Mikuni VM carbs modified and set up to suit.

We can also supply slides only if you prefer, or even carbs fitted with conventional brass slides.

Plenty of other TZ carb parts available, just ask for more details…
Mikuni VM38 26J Reverse Slide Replica Carbs Built by Allens Performance Ltd

Jimmy Doom Special Doomster Engine

September 4th, 2016

Feast your eyes on the Mammoth Vee Twin of Doom!

Here you can see a prototype for a run of extra special engines conceived and developed by the most eccentric Cylinder Head guru in the North, Jimmy Doom.

The bore/stroke of 4.250″ x 4.250″ gives a total capacity of 120 cu in (around 2 litres.) 2.100″ valves are fed by VM44 carbs supplied by Allens Performance Ltd. Cam lift is 0.650″ and the exhaust headers are a full 2″ diameter.

Doomsters are destined for a new wave of muscle bike so watch this space!


Allens Performance: Delivering Carburation Innovation Since 1983

October 9th, 2015

You will find most knowledgeable, long standing people in the motorcycle industry will already know about Allens Performance and its reputation.
Anyone who has looked for long at a carburettor has probably marvelled at the complex appearance of these precision instruments intended to give you the perfect mixture of well atomised fuel in air despite the demands of varied load and speed conditions.

Making all this happen is not a black art as some would have you believe. In essence, a carburettor is a simple collection of pipes, metering holes, fed by a pressure difference and a pool of fuel. However because there are so many unknown quantities involved it does require plenty understanding, logic, experimentation and experience to get things right. Allens Performance will help you achieve the perfect burn!

Allens Performance can help with mail order. Genuine parts for Mikuni and Keihin (aftermarket) carburettors, and can now also offer a limited range of parts for Mikuni OEM carbs. Additional parts Tomaselli, Domino and Leonelli controls, custom made throttle cables, Aktive reeds (for road race and MX, etc) Other services Allens Performance can provide:

  • Carburettor servicing, reconditioning and restoration
  • Ultrasonic cleaning and media blasting
  • Engineering solutions to repair and rescue difficult to obtain carburettors and parts
  • Consultation and setup service on location available

Suzuki XF650 Freewind Special Carb Set with TPS

December 15th, 2014

Another job to keep the Allens workshop busy! Not the billet Throttle position sensor adaptor on this special rack of smoothbore Keihin CR33 carbs for a Suzuki XF650 Freewind engine powered CCM. Pictured here next to the original Mikuni BSR CV carbs

.Special Rack of CR33 Smoothbores for Suzuki XF650 Freewind CCM with TPS