Taking a grinder to Britain's motorcycling heritage.
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Sunday, 2 January 2011

Norton Commando

This is my mate Andy's 850 Commando, a really nicely prepared bike that has been put together with a great eye for detail. The problem is the nice looking Roadster tank is fibre glass. Since the law has been changed and petrol companies can use a higher proportion of vegetable based Ethanol in modern fuels a lot of older bikes are suffering. If they are fitted with fibre glass tanks, or have a fuel tank sealant in their tanks they are in trouble. The Ethanol breaks down the resin in the fibre glass or sealer and it dissolves into the petrol and goes through the carbs and head as part of the fuel. The first time this happens and whilst the motor is hot there's not a problem, when the motor cools down again the diluted resin comes out of suspension and leaves a sticky brown residue on any surface that it has been in contact with, carb internals, valve stems, piston crowns all that kinda stuff. Once it turns into this brown mess, the next lot of fuel coming down the pipe does not re-dilute it again, meaning that it just builds up.This now means the whole of the top end has got to come off for cleaning, the petrol tank is scrap and the carbs may also have to go in the bin.
If you are running tank sealer or a fibre glass tank, consider this a warning.

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