XJ600

Hi All.

Can someone help me, I have a xj600 1990 with only 12000 odd miles on it and its now running poorly,

I've put new plugs and air filter on but with no joy.

It seems to be chocking up with fuel and missing after about 15 mins of running and wont tick over.And then fails to re start.

The carb are clean and fresh petrol.

I can clean the plugs and the next day it starts but all of above happens again.

Anyone out there with any idea of whats wrong.

Thanks

Jon