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

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

125 Bantam Class

March 26th, 2000

125 Bantam has become a championship contender after only 3 years development!