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Carburettors need love and attention
Simply put, your carburettor is a mechanical measuring device. It takes fuel and air, mixes it in exact quantities and then sends it forward into the combustion chamber. How it does it is much more complicated. The inside of a carburettor is full of narrow fuel ways, needles, butterfly’s and float chambers which control the flow of air and fuel.
The bodies, which you see every time you open the bonnet, are almost indestructible and it is easy to pay scant attention to their inner workings. They also tend to ‘go off’ over a period of time, allowing us to get use to that stutter in performance, rich fuel smell or extra few cranks when we start the engine.
So what goes wrong?
- Stale fuel congeals inside the carburettor, blocking up fuel ways or gums up its workings
- The floats can become porous and fill up with the fuel they are suppose to be displacing
- The rubber seals can perish, split and leak
- The gaskets can leak or let air in
- Springs can loose their fight
- Fuel needles can either be incorrect or damaged
With few exceptions, carburettors can be brought back to their original condition with little more than a good clean, new seals and a measure of patience. Here at Project Shop we have rebuilt hundreds of carbs and have only found one or two which were truly past it!
The process involves 5 phases:
- Checking the insulation. Making sure there are no intake leaks and that throttle/choke linkage and cables are secure and work together. Often the job can finish here when linkages have become loose or cables seized in their outer sheaths.
- Remove and strip – Sim often covers his eyes at this point. The bench is covered in hundreds of tiny, important parts. They are all cleaned and checked and a list of replacements compiled.
- The rebuild – Once the parts are collated we can ‘simply’ put it back together and get it back in the car.
- Tune up – Using a set of balancing gauges, an ear and a flat head screwdriver the magic can start. At this point you are making sure that the fuel and air mixture are correct, the engine will idle nicely and has plenty fuel and air as the revs rise.
- Test drive – The final fettle is always done on the road. Making sure there is plenty of performance and the engine is running smoothly when it is both hot and cold.
We have experienced most carburettors, know where to buy the bits and how to set them up so if you think that your engine is lacking some punch, give us call.