carbs have been running okay then suddenly one plug starts to foul up turned mixture screw in still runs rich any ideas ?? was thinking could be a bit of crap in the carb any other ideas

Swap 'em for TBs?

thinking about bike carbs any suggestions

keep the twin 40's and just give them a clean

ditto, just take them apart and clean them. Do make sure you have good fuel and air filters fitted. Blocked jets tend to starve the engine off fuel so it’s unlikely to be that.

Also check the cold start system is turning off and that the fuel float needle valve is sealing properly, might be worth shaking the float to see if its been filling a bit with petrol and sinking. That’s quite a common problem with carbs and often noticed on bumpy country roads. If it is, simply place it on a radiator and the fuel will evaporate out. Some epoxy will seal any pinholes.

removed the jets today gave the carb 100psi through an air line and voila all sorted, cheers for your comments and advice