Dave you make no mention as to whether the engine even attempts to fire or even misfire...and that the plugs are found to be wet... which caused me to suggest a fuel issue, though forgot to mention my thinking was on the quality of the fuel. Modern fuels seem not to age well failing to ignite when a spark plug fires, thus my suggestion of trying some easy start which would perhaps assist in fuel quality assessment..?
The bit of rubber, yeah well modern fuels reportedly can cause issues relating to fuel line materials degrading, though also worth considering is that when pushing a rubber tube back on to a metal fuel line the tube can nick the very edge of the inner diameter of the rubber fuel line, causing it to enter the carbs, though my dim memory thinks that there may be fuel filtration in the area of the carbs fuel supply connection which should inhibit even something as small as you found from entering the float bowl needle..?
If it does not even bang or f*rt, but sparks are present....I would start with the simple stuff...
Given the normal pump jet ops on Webber`s regardless of any jet function I would expect it to try to fire....?
Claiming zero expertise and just thinking in type...
Feedback required to try to assist you further Dave..?
