Rocco wrote:
could it be something to do with the timing?
Doesn't sound like it. Is it a regular 'miss' or just general rough running?
Check that you have all gaskets between the carbs and the manifold, with heatsheilds, spacers etc, it is easy to over look this.
What sort of manifold gasket are you using? Black 'soft' one or hard red one?
Is the manifold actually tight against the head? If the flanges between the inlet / exhaust manifolds are different thickness's, they won't seal.
Has the manifold and plugs or bungs in it? Check they are sealing.
Got a PCV crankcase vent set up? Sealing OK, PCV Valve not leaking?
Got a brake booster? Disconnect the vacuum hose and block it off to see if it makes any difference.
Is the piston(s) in the carbs moving OK, not sticking?
Jets clear and no crap in them?
Choke coming right off on both carbs? Check that the jet under the carbs is seating home.
What air filter set up do you have? Gaskets / mounting plates etc not blocking the vents for the Carb Piston(s)?
Vents for the fuels bowls open and clear?
Fuel OK?
Fuel Pump pressure in the right range (3.5 - 5.5 PSI) ?
Done a compression test?
Pics of you set-up?