stumpshot

Actually, the problem is my stupidity. We left home for the winter (3 months) and I filled all the rigs up with fuel and forgot the 75. It sat with a 1/4 tank the whole time (in the garage).
Got back, fired it up, went to the gas station and everything was fine but it was only 5 miles. Coming home--- suddenly missing and rough except at 1/2 throttle which takes off like a raped ape and still has a misfire going on. Get home, check for vacuum leaks--nope. Vac advance----fine.
Timing---right where I left it. Haven't pulled the inline fuel filter yet because I'm waiting for the car to cool off. Accel pump has a good shot of gas coming in. The engine is a Smedding 383 with a Quick Fuel 700, vac secondaries, auto choke.
I've never torn a QFT carb down for cleaning and I really don't want to unless I have to. There's no popping or back firing at the carb or the pipes so I kinda rule out electrical crap cutting the spark and then coming on again.
Any thoughts appreciated!

sunflower 1972

Before tearing the carb apart, I'd try dumping 1 or 2 bottles of HEET fuel additive and drive it.

drwet

Before tearing anything down, I would drain the fuel and put in some fresh fuel from another gas station. I can't say the symptoms definitely suggest bad gas but the circumstances certainly do. I have also had it happen to me that I did a bunch of work trying to track down a rough running problem that turned out to be bad gas.

sunflower 1972

HEET Brand FAQ's:https://www.goldeagle.com/brands/heet-faqs

Jims427400

I 2nd the Heet. Had the same problem years back. Bottle of Heet with topped off tank of premium and it gradually cleared up.Draining the tank will address it as well.

stumpshot

Thanks guys. Living in California we have so many additives in the fuel there's no room left for gasoline. I never think of additives except in my diesel. I'll pick up the Heet today and see what happens.
The fuel filter was clean.
Thanks again!
​​​​​​​Stump