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

Benelli Sei Six Cylinder Keihin CR Carburettor Rack

June 12th, 2019

The latest off my bench: A set of specially built Benelli Sei Keihin CRS26 26mm racing Smoothbore carbs. Built to order, replacing three standard Dellortos, special spigots made to fit individual manifolds, imagine the sound!
Benelli Sei Kehin CRS26 Smoothbore Carb Set, Allens Performance Ltd, Rack of Six

Thanks from Lewis Ranger

December 6th, 2018

We do aim to please Lewis Ranger!
Leis Ranger 2018 British Clubman Enduro Champion Husqvarna TX150 RangersKe

December 4th, 2018

Next time you’re rebuilding carbs with repair kits, bear this in mind.
Pattern (Left) vs Genuine Float valves under the microscope. Hmmm!

Pattern Float Valve Example

Genuine Float Valve Example

November 28th, 2018

Another nice home for an Allens Performance carburettor!
A Mikuni VM26 looking pretty on a Moto Guzzi Falcone 500cc.
Mikuni VM26-8637 on Moto Guzzi Nuovo Falcone 500cc

Suzuki GSXR750WP FCR39’s

July 26th, 2018

The most recent carb build, shaft made at Allens. The next time you see these, they should be racing around the Isle of Man at the Classic TT!

Keihin FCR39 Horizontal Carbs Suzuki GSXR750W Respaced Allens Performance Ltd

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

CR 29 Smoothbores, Kawasaki Z1000

March 7th, 2018

Just finished! One lucky lad will be able to replace those nasty CV’s with a set of beautiful Keihin smoothbore CR29’s. Complete with specailly made airbox adaptors by Allens.CRS29 Z1000 Carbs carburettors with special Airbox Adaptors


TM24 Flatslide Plus Solenoid Controlled Powerjet

May 25th, 2017

Some powerjet conversions are more work than others… The TM24 really isn’t designed to be used this way. But nevermind, we have a milling machine and we can be stubborn at Allens Performance!

Mikuni Tm24-9 with electronic solenoid powerjet conversion

April 19th, 2017

Here we go!

Replica Yamaha Race Kit Exhaust Flange Castings ready to be machined at Allens Performance.

Many possible applications include RD350LC2 YPVS, TZR250 RD500, RD350LC.


Replica Yamaha Race Kit Exhaust Flange Castings RD350YPVS TZR250 RD500 RD350LC