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my virago xv535 is a 1990 uk model and will only reach 65-70 mph downhill with a good tail wind. the rear cylinder is smokey on warm up and pops on full throttle. i know the carb diaphram has a small split in it but would that cause all my grief?

smokey? what color is this smoke? if its got a radiator, that adds to the equation that it could be burning coolant, which indicates a cracked block. but lets assume its a fuel problem, which is what it sounds like.

the smoking could even possibly be related to a potetnial fuel problem...if i had to guess, i would say youre running rich. the split in the diaphragm (if im remembering correctly) would definitely be a problem, as it has much to do with the correct fuel/air ratio delivery.

i could have a few things a little sidetracked, but i believe your best bet would be a rebuild kit and cleaning for your carbs.

the piston that is attached to the torn diaphragm has a needle in it that fits in the main jet.if it dont lift up out of the main jet all you are running on is the slow jet.

thanks guys this helps, it is air cooled so coolant burning is not a problem but running rich she could be, when sitting at the lights it does smell of petrol. i will have to source a cheap diaphram then see if it improves, i was wondering if i could patch it up for a couple of weeks till new one arrives, with silicone or even vulcanising rubber from a punctur repair kit or something like that. cheers ... Steve

i think your better bet would be the vulcanising rubber, if it were between that and silicone. i imagine it would be difficult either way, because it cant be too thick, or too thin. good luck

i patched one with some black silicone and it held up ok.have to give it ample time to dry.