<VV> Re: main jet vs idle, Plug fouling. Longish

[Padgett]

 >Is it possible that the fuel pump is weak (leaky valves?) and isn't pumping
at low RPM.   Engine goes lean.  Rev it up and refill carbs... <

Fuel pump was just replaced by PO a few months ago. Just ran the following 
test: Ran engine until warm and idle did the drop from 650 to 400. Ran 
there for a minute or two and allowed to die on its own. Removed carbs. 
Both bowls were filled equally and to the right level..

 >All other things being equal, if you notice that the difference in the 
adjustment of your mixture needles is significant (say one turn out vs. 
three on the other), it might indicate you have mixed clusters.<

Both carbs are balanced to the Unisyn and have the same mixture (2.5 turns 
though 2.0 turns seems the same) adjustment and close to same idle screw 
setting. When apart day before yesterday I did not notice any difference in 
the clusters but only looked for both to be asymmetrical. Same for internal 
parts.

Given that one carb was nice as bought and the other had considerable 
sediment and was missing the PE needle, anything is possible.

I really think the carbs are close since 650 rpm in drive while it lasts 
(which has been several minutes) is nice and Unisys shows good balance both 
at low idle and at 2000 rpm. Really feels to me as if one plug is fouling 
and another goes  in sympathy when the revs drop.  Just looked at #3 and 
looks essentially new except for dull blackening. Looks a little like the 
cold or carbon fouling illustration in any generic Chilton's manual but 
also looks a lot like any other used plug I've pulled.

Let me reiterate: From cold start (is a touch cold blooded so wants a bit 
of extra throttle at first, may just not have enough fast idle it warms up 
nicely. Once chokes open fully idles is a nice stable 650 in D (will hold 
800 all day in N).

At 800 rpm in N, pulling each plug wire in turn results in a drop of 60-80 rpm.

After a while (can be minutes, can be seconds, usually comes on quickly 
once starts ) "something" happens and idle in D drops to 350-400. Pulling 
#1, #2, or #5 kills engine, #3 or #4 nothing happens, and #6 is somewhat 
anomalous. All plugs (W8AC with about 300 miles and hours of idling) have 
black (not oily) insulators and electrodes  (may be from too much idling) 
but all look about the same. Revving to 2000 in N for a while (15-20 
seconds)  restores the 650 in Drive idle for up to 20-30 seconds, then 
drops again.

I will find the solution but have to replace the idler pulley before going 
anywhere since can feel vibration in housing and is quite noisy under 600 
rpm. May just go to a hotter coil to match the Pertronics Ignitor II. 
Should the gap change with this combo or should I keep it at .030 ?

Padgett