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I have tried setting up the carbs but get very rough running at medium/high revs and the engine reaches about 4000rpm and no more. Any ideas? I have tried every setting known to man. The front float valve was sticking and that's now sorted. The front carb piston can be manually moved up through the intake without major effect on engine revs, but the engine dies when the rear one rear one is moved up.
The engine was running rich, or so I thought, due to rich smoke, and hence the investigation...
many thanks

Go back to book settings and make sure the throttle discs are fitted and set correctly,then balance and set the tick over ,refit air filter assembly and take for a run.I fitted new plugs as mine was runnig rich on the rear carb and the plugs were well and truly mucked up.I didn`t think it was running well after following this routine untill the air filter assembly was refitted.After a mile or so it ran really well and has done since.I don`t think revving it up at a standstill shows how it`s running really ,needs to be under load on a rolling road or the real road.Mine had been ran regular over the past 10 years at a standstill but it had choked up with carbon from not having a proper run on the road, so after a proper run and the carbon was burnt off it just seemed to get better and better.Hope this helps,it did for me.

How long has the car been off the road?

Don't forget timing. Vacuum leaks can also compromise the advance/retard of the ignition causing rough running & poor combustion.

As Jagaz says the more use the better...

Hello Thunderbox,

a simple check is to remove the dash pot dampers and rev the engine, both pistons sgholu rise together. From what you say it doesn't sound as if the two carburettors are balanced?

Alec