[Spridgets] Why Does Engine Like to Run Rich?

[Peter Caldwell]

Real quick coupla things.

Number of flats down is from the point where the jet is level with 
the bridge.... it's not 12 flats from all the way up. You should see 
fuel about a 1/4 below the top of the jet when the bowl is full to 
the float shut-off.

The needle's shoulder must be flush with the bottom of the piston, 
not up inside, or protruding.

Soot may not be from richness, aka unburned FUEL, but from deposits 
of the unburned (and unburnABLE) additive in today's unstorable fuel.

Fuel for thought.  Gotta run

Peter C


At 09:17 AM 5/26/2009, Doug Altman wrote:
>Stock 948 with good rings, stock rebuilt H-1 1 1/8" SU's.  I've adjusted the
>carbs per the workshop manual, used Colortune, and even Frank's trick of a
>standard 2 1/2 turns down (15 flats) on the jet adjusting nuts several times
>over the past couple of years and they all point to running a lot leaner than
>where the engine runs best.  The engine starts, runs, and accelerates best at
>25 flats down (over 4 turns) on both carbs.  Right now it seems to accelerate
>best when the front carb is even at 30 flats (5 turns) down.  I've tried rich
>needles but it runs for crap with these.  Spark plugs are always black and
>sooty.  Why does it like rich?