34 Pict-3 Oversized Mixture Screw

[Anky1978]

Hi all,

I’m trying to optimise my mileage in my ‘72 Superbug. The best I’ve gotten is about 15 mpg (~15L/100km), which isn’t terrible but not great given it’s a fully rebuilt motor.

So I checked my 34 Pict-3 for servicing. I never thought it to be unusual, but the mixture screw is massive and sits in a sleeve wedged into the carburettor.

Must have been a jury-rigged solution. I tried to replace it with the smaller screw in the servicing kit, but it just spun freely and took a good hour to get back out again. So I put it back in, but as you would expect, there is a vacuum leak detectable when spraying carburettor cleaner all over the mixture screw.

When I pulled it apart, it had some hard red epoxy around it that must have been there to stop the leak. Any ideas on what I can use to seal up that gap without damaging the carburettor body?

[anthax]

Source another carb and rebuild it. Or if it's possible to put in a small thread insert.
But 15L/100km? That is horrible! My 2L drinks just over 0,6L/100km. o.O

[bnam]

Put some sealant between the carb and the insert. See if that stops the leak.

If it does not, remove the screw and take it to a machine shop to have a small cut made on it to seat an o-ring. Between, these 2 options your leak should be solved.

I’m assuming the screw has been shaped appropriately to match the original - u can compare the tip with the new one.
_________________
1971 1302LS Convertible (RHD) owned since '74
Click to view image
1965 Karmann Ghia Coupe - under restoration
1966 Fiat 1500 Cabrio (with 1600 Twin cam)
1952 Citroen TA 11BL

[Pruneman99]

15 mpg is pretty horrible. I get 30, and probably don't have the best tune. I don't really take care of my car but it just keeps on going..

There might be ways for a skilled machinist to repair that, but honestly, I'd just try to find a new carb. OG ones properly rebuilt are probably best. I'm running a PICT34-3 from Volksbiz I'm happy with.