Q: Having recently acquired a 1984 TY250 trials for restoration but I find myself with a plastic fuel tank that has a nice yellowy tinge to it. Is there any way of returning this it to its former (white) glory?
A: Opinions vary on the cause of this discolouration. It is tempting to imagine that it is caused by the effect of the fuel on the plastic, but some owners have found that on removing the stickers the plastic is found to be in perfect condition, and thus the conclusion is that the damage is being caused by sunlight, specifically ultra-violet light. However, this is not a completely sound scientific test.
You could try polishing the surface with very fine wet-and-dry paper and then car polish to see if the discolouration is on the surface only, but probably the best course of action would be to cover the plastic with a tough and impervious paint. Paint will stick perfectly well to plastic, using the correct techniques. You might speak to a local paint sprayer who could offer advice.