[Spridgets] Why Does Engine Like to Run Rich?

[Doug Altman]

Needle shoulders are flush with bottom of pistons per instructions.  Jet
adjusting nut is all the way up, entirely compressing the spring when I start
to turn them down.  This has always been my starting point.  I'll check the
jet height when the nuts are all the way up.  When I do have the carbs leaned
out to where the Colortune says they should be, I get nice, gray colored, dry
plugs.  How do you see the fuel level in the float bowl to compare it to the
position of the top of the jet?  If you take the top off the carb, the float
comes out too and the fuel level changes (?). 
________________________________
From: Peter Caldwell <peter at nosimport.com>
To: Doug Altman <doug_altman at yahoo.com>; spridgets at autox.team.net
Sent:
Tuesday, May 26, 2009 11:08:13 AM
Subject: Re: [Spridgets] Why Does Engine
Like to Run Rich?

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?