> 1- Therefore turning this nut LEFT [counter clockwise]
> should LEAN the carb out?
That sounds right to me, Cosmo. Another way to look at it : moving the jet
higher in the carb body will lean out the mixture, so you are screwing the
nut onto it's threads for leaner; unscrewing it for richer.
You should also be able to verify the results of your changes using the
"lift the piston" test. Using either the pin provided on the side of the
carb, or a knife or similar down the throat of the carb; with the engine
idling, lift the piston a small amount (roughly 1/8"). If the mixture is
rich, the engine speed will increase and stay up as long as you hold the
piston. If the mixture is lean, the engine will immediately stumble and the
speed will go down (possibly even stopping the engine). When the mixture is
just right, the engine speed will rise slightly and then settle back to the
same speed as before.
> 4- Is there anything else I should be doing to 'Just lean
> out the carb' more?
The mixture nut should have far more range than you can use. Honestly, I
don't believe you will find better gas mileage that way; as lean fuel/air
mixtures do not burn as well and therefore tend to be less efficient. It
takes many other changes in engine design (combustion chamber shape, intake
& exhaust changes, ignition, etc.) to effectively burn leaner mixtures; and
even then there is minimal improvement in fuel mileage.
I should also point out that there are many dangers in running a lean
mixture; it can actually damage the engine. The first TR3A engine I ever
worked on wound up being pretty well destroyed as a result of lean mixture
under cruise conditions (caused by worn jets/needles in the carbs). Since
the overly lean charge burned so slowly, it was still burning when the
exhaust valve opened; which overheated the exhaust valves. The stem under
the head eventually eroded so much it broke. End result was pieces of
piston and liner spread all over the road.
Randall
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