Hi Sean.
With the 60 primary idle jet you should be getting a good idle. Going by the
air/fuel ratio meter I have hooked up, the idle mixture is quite sensitive to
adjustment. You can go from full scale rich to no reading lean in just a quarter
turn of the idle mixture screw. Without the meter, you can tune by ear. Just
turn the screw in until is starts to run a little rough (it will be very lean).
Then back the screw out until it smoothes (fully rich e.g. 12:1). Don't worry
about running a little rich at idle. It helps a smooth idle and you don't spend
a lot of time at idle. At least I don't.
I wouldn't change to larger idle jets (60, 50) just yet. Check for air leaks
using propane around the intake manifold near the head and the base of the
carburetor. If you detect no speed up, there is no air leakage.
Coming off idle, the transition is covered by the progression jets just above
the throttle plate. These also use the idle jets to regulate flow. If there is a
blockage in these, the engine will hesitate or stall as you apply throttle.
If it dies after a few seconds of full throttle, then I would check the float
level. Apparently, two floats types were used, brass and plastic, and each had
a different level setting. Which type do you have?
Have you checked the timing? I use 10 degrees BTDC at idle, without the vacuum
advance connected.
Vic Whitmore
76 Spitfire
Thornhill, Ontario
http://www.vicwhit.com
S Twigg wrote:
>
> Vic,
> It still wasn't running correctly after a number of adjustments.
> First, I had an air leak through the secondary throttle plate. When I fixed
> that I went from running extremely rich with a main idle jet of 60 and a 50
> secondary, to running very lean with the same setup. It would idle ok with
> the idle mix screw out three full turns but would die under load. I'm
> waiting on a set of larger primary and secondary idle jets to see if this
> corrects the problem. Currently, I have a CD150 on and it is also as lean
> as possible. Also, it likes to cut out on me at stoplights and stops after
> running for a while, not a heat problem, as I have the shield installed . I
> need to check the float level to see if I'm flooding out.
>
> So that's the saga,
>
> Sean Twigg
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