EXPERT’S GUIDE TO... CARBURETTORS
Old bikes are lovely – but worn or neglected carbs can drive you nuts. Here’s how to sort them out
Steve has run aftermarket carb specialist Allens Performance (allensperformance.co.uk) for 10 years. He is a mine of technical advice, and also an expert on two-strokes. Think of your carburettor as having a big pond of fuel at atmospheric pressure. At the top you’ve got air flowing into the engine through a restricted diameter, so that reduces pressure, because the air has to increase the speed to maintain the flow. This causes fuel to flow from the bottom of the carb, through the jets, to the top. That difference in pressure is what we call the signal strength. The trick is to get a signal without restricting the flow of the air too much. The flat slide CRFS, TMRS and FCRS we sell are basically as far as development went with the motorcycle carb. Their very short venturi give the maximum signal strength for the minimum disruption.
These flat slide FCRS are basically as far as development went with the motorcycle carb Carbs offer perfect fuelling… but only when they are in good nick