"David C.Willett" wrote:
>
> I suspect all you experts on this list are going to roll your eyes at this
> enquiry,
David :
No problem, we were all newbies once, and sharing knowledge "from those
who have BTDT" to "those who may follow" is what this list is all about.
> I balanced the air flow
> as best I could using a length of tubing, then with the engine idling at
> about 700rpm, I lifted the piston of one of the carbs the requisite 1/16
> inch, at which point the revs increased slowly, supposedly indicating the
> mixture is too rich : I turned the adjustment nut one flat up (leaner?) and
> found to my suprise that the nut was virtually at the end (fully closed) of
> it's travel.
> Does this mean that the jet/needle is so worn that there is fuel flowing
> even when the throttle is closed?
Worn jet/needle (caused by incorrect jet centering in the past) is one
explanation of your symptom, but a more common one is that the upper jet
seal is leaking. The original seals were made of cork, and in my
experience simply don't last very long. Until I switched to the rubber
(Viton ?) seals sold by Moss, I had to replace the cork every year or
two. There is also supposed to be a copper seal between the upper jet
housing and the carb body, this area can leak if the seal is missing.
Other possibilities include :
Binding piston. With the damper plunger removed, the piston should move
easily and freely. If it rubs or binds in any way, you need to find the
problem and fix it. With the plunger installed, and the dashpot full of
oil, you should be able to press the piston easily (although slowly) to
the top of it's travel, then release it and have it fall smoothly and
rapidly with a definite 'click' at the bottom. No 'click' may mean your
jet centering is off.
Wrong spring inside the vacuum chamber. If there is any doubt yours is
correct, it's worth buying a new one to compare with. (They're only
about $3 from Moss.)
Excess deposits on top of the vacuum piston.
Fuel level too high. (Misadjusted float level, leaky needle valve, leaky
float, fuel pressure too high, etc.)
Missing or broken spring and washers between the jet seals.
High overlap (non-stock) camshaft.
Incorrect valve timing.
I'm sure there are others, those are the ones I can think of off-hand.
Randall
59 TR3A daily driver
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