Hi
I have a strange problem with a "misfire" at speed only

When accelerating fast, and getting to about 6k in fourth, a misfire happens, that is so bad that the engine does not want to run over tickover speed

If I stop, and restart, it will be fine to drive untill I re accelerate, (foot to the floor type)
since this problem started, I have done the following to the engine

head off and relap valves (no1 was a bit lower than the rest, but all are the same now)
rebuilt the carbs (twin 40s) new service kits etc and a good blow thru
changed from engine driven fuel pump
to electric, the fuel line has been blown thru
had the fuel tank modded to give a sump, of around 1 gallon to avoid surge problems

changed the lumention ignition and coil to
a differant type, all except the distributer pickup

dizzy cover and rotor arm plugs and leads are less than 1k old, so should not be the problem, but i will change them, anyway

any one got another idea ???

regards

steve

Classic fuel stravation symtoms -- first check the tank is venting, then check the pipes are clear --- disconnect at both ends and blow through from engine backwards (use foot pump or compressed air).
Check fuel filters.
Check there is no rubbish floating around intank. Then road test.

If missfire still present check fuel pump delivery rate and pressure, carb float levels and that there is no dirt above the float needle valves in the carb.

One other question is the problem still present when the tank is full -- if it isn' it could be fuel surge.

Yep fueling, check carb, fuel lines, tank & vents. Most likely in the carb, then you are going to be looking fora small piece of foriegn matter possibly about the diameter of a human hair. or something larger bloking the air corrector vents in the top of the carb.

Enjoy.