I'd try an get a key cut Mick. Trying to get into the tank to replace the filler cap is a right swine. I've had to do it twice and both times I've managed to bleed all over the thing.

Getting the ign barrel off is easy, just take the yoke off. That is unless you've locked the steering and then lost the keys. I've done that too!
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If I have to take the carbs off once more...