Anybody know why my 2 ltr dual carb kombi might do this?

Oh, any only just about run on what feels likr two cyclinders if i pump thottle like crazy.

I've just checked compression, 125 all round and have 4 sparks.

cheers
swampy

Maybe you might have the carbs incorrectly tuned and/or a tight valve or two.
Does it happen only when the engine is warm or only when it's cold?
Does it also backfire out the exhaust?

If you pump the throttle like crazy then it will tend to lose cylinders, because they are flooded and dont have enough air to fire.

Oh sorry, just saw you checked the compression, probably not the valves then.
Check the timing, might be too advanced

timings good, is 30 btdc at 3000 on a 009

hot or cold:cry

hmm, are you sure that is the correct timing setting?
hopefully someone with knowledge on buses can shed some light in the morning.

a backfire through the carb is a sign of leanness

99% says you have a blocked idle jet of circuit

Seeing as thet are dual single barrels that will make it run on 2 cylinders