Triumph Repair: Stromberg carbs, vent line, engine didn

Question
I have a 76 spitfire and a 72 GT6 both have carb problems,the Spit doesn't idle all that great but runs not bad at medium usage say up to about 50MPH over that it backs off and i had a nightmare run back from the lake where it would backfire after it started to do the backing off?  The GT6 was running fine then suddenly it would slowly run down until it stalled, we checked all tune up components all replaced so we thought of vapor lock changed the filter no luck,my son then realised that although we had spark to all cyls. the front three weren't actually doing anything you could pull a plug wire and the engine didn't change,we've ended up changing all the fuel lines and removed the tank because we had bubbles in the fuel filter,put it all back together and now the front carb is flooding.We took the carb apart and did a general clean up and checked the float it didn't seem bad put it back together and it ran great for two days and now it's doing the same thing again,very frustrating after all that work and with our short Summers the car has been off road for too long.Any advice welcome.

Answer
Hi Barry,
The spitfire should have a compression test first and tell me the readings.
Since you worked with the float and it fixed it for a while you need to look again at that system. Check the float needle and seat and the float itself and float chamber vent line.
Howard