<VV> Idle Speed (long... enter at own risk)

[Mikeamauro at aol.com]

Re: idle problem after warm up.
 
Tom:
 
I believe you stated the can ran OK until after warm up. This is  symptomatic 
of a too lean condition occurring after the chokes open. This could  be 
caused by "trash" in the idle circuit, idle adjustments screws turned in too  far, 
throttle openings misadjusted at the idle position, or a combination of all  
three. The throttle plate position is best handled using an air flow device 
such  as a Unisyn; as you likely don't possess a Unisyn, and I'm assuming the 
throttle  plate at idle adjustment was OK before idle problem developed and has 
not  been tampered with, lets look at a couple of things you can try on the 
first two  possibilities:
 
Try Clearing Trash W/O Disassembling Carbs:
 
1. Warm engine. 2. Stop engine and remove filter and intake sheet metal  
until the tops of carb intakes are exposed. 3. Start engine, and  being EXTREAMLY 
careful of where you place your hands, use carb linkage to  raise engine RPM 
to about 3,000 (not wide open, but a mid-range type of sound);  with engine 
speed held elevated, firmly place the palm of your hand over each  carb several 
times in turn, for about a second each time to completely  block air flow (you 
should end up a bit of raw gas on your palm; this is  normal). By blocking the 
main intake portion of the carb, with elevated vacuum  potential at partial 
throttle, "trash" if not severely lodged in the idle  passageway, will be freed 
up and pulled out of the carb.
 
If, after above attempt to clear "Trash" the idle is still N.G, with engine  
warmed and in neutral: adjust Idle Mixture Screws (these are the screws that 
are  on the inboard side of each carb, and enter diagonally near the base of 
each  carb):
 
1. Counting the number of turns, adjust the idle mixture turns out one carb  
at a time, one half turn at a time. 2. Turning outward (to the left), at  some 
point the fit of the mixture screw might get sloppy; if this happens  before 
the idle smoothes out, then the mixture adjustment on that side was  not the 
issue: return mixture screw to original position. While turning screw  IN, if 
idle worsens, back screw to left 1/2 turn and move to the other  adjustment 
screw. 3. Repeat process on both carb idle mixture  screws. 4. If PG trans; set 
hand brake FIRMLY and recheck idle with tranny  in gear. When everything is 
right, you should be able to turn either mixture  screw in about 1/2 turn to make 
the engine stumble at idle, and turning the  screw back out 1/2 turn (to the 
left) should restore a smooth  idle. 
 
In none of this works, the next things to do, before tearing the carbs  down: 
check all sources of possible vacuum leaks: lines/connections, vacuum  break 
on top of carb (plastic with a vacuum line attached) and vacuum  advance  (but 
probably not be the advance, as no vacuum there at  idle). 
 
Still NG... find someone with a Unisyn and make sure carb idle throttle  
plate positions are balanced one side to the other; and as carburetors open past  
idle, air flow through carburetors remains relatively equal. If you are not  
handy, you should look for help with this process the first time. Do all the  
preceding before resorting to tearing the carbs down. And, if you don't have a  
shop manual, get one and read it each night as a bed time  story. 
 
Good luck,
Mike Mauro 




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