cab not running well

1800, 8 valve, manual choke.

Can anyone suggest where to look next………
Under load (3000 revs it seems) my cab runs like a bag of spanners. Kangarooing spluttering and then almost stalling.

changed plugs, coil, coil pack and leads. Dizzy cap doesn't seem to have cracks (checked in the dark) she starts 1st time every time even in the cold and wet. ticks over fine, purrs actually.

costing me unnecessary cash but can't seem to get to the bottom of this at all.

thanks

sounds like your not getting enough fuel through.   you may have a rusty filler neck dropping bits into the tank and then blocking up lines/ filters

do these carbs have 2 jets, cos you main jet sounds blocked.


or it could be fuel starvation due to causinG A VACUUM IN THE petrol tank.
remove the petrol cap and see if it goes away