Rebuild And Fit Bike Carbs

Don’t break the bank balance with throttle bodies. We’ve found the cheapest solution to performance fuelling: a set of four bike carburettors.

There was a time when a fuelling system was cheaper than a second-hand engine. Nowadays, a new pair of 40 mm carbs and an inlet manifold can almost be as expensive as a set of throttle bodies or an aftermarket fuel-injection system. One alternative solution is to fit a set of motorbike carburettors. This is a popular solution for inline four cylinder engines with four inlet ports in the cylinder head. A set of four carburettors from a Honda Fireblade, Blackbird, Kawasaki ZX, Suzuki Bandit or Yahama R1 for instance, can be fitted using a suitable inlet manifold, which is manufactured by a number of specialists including Bogg Brothers and Fenspeed.

Budget for under £200 for a suitable inlet manifold, £100-£150 for a set of carburettors and another £100-£200 for an air filter, manifold gasket, motorbike fuel pump and cables (choke and throttle).

We visited Bogg Brothers to find out how they stripdown, inspect and modify a set of carburettors from a Yamaha R1, so that they can be fitted to a four-cylinder car engine. These carbs have 40 mm chokes with 1.3 mm diameter main jets. The main jets need to be enlarged to feed a larger car engine. This can be completed with an electric drill. The enlarged diameter varies in size according to the engine the carbs will be fitted to, but Bogg Bros can advise on this subject.

We also visited Chester Sportscars, who offer a comprehensive bike carb conversion package comprising all the aforementioned items, plus an ignition kit with coil pack and suitable sensors. Their bike carb conversion kits start at £510 for the fuelling components, up to £1008 with ignition management and parts (coil pack, HT leads).

So what are the benefits of four bike carbs? A more responsive throttle pedal, easier maintenance and straightforward cold starting with a manual choke are some of the answers. You won’t get more performance over a pair of Webers, but they are often cheaper, just as reliable, more fuel efficient and easier to set up.

The following pages cover stripping down and modifying Yahama R1 carburettors and fitting a set of motorbike carbs to an engine. The information acts as a general guide, so it’s worthwhile speaking to the specialists we’ve mentioned for specific advice and parts on your own Ford. Set aside a weekend to complete all of the work shown.