Ok hang on; Ima gonna attack this from easiest to do, to hardest, and jump around logically.
So the easiest is to suck the bleeds out (see test#1),
Next is to clean and gap the points if your engine has such, then check that the ignition timing is at least close.
Next up if you have a solid-lifter engine, is to reset the valve lash. (I like .013intake/.023exhaust, on a warmed up engine), then
next is a compression test. While the plugs are out, you check them over looking for cracked insulators, and regap them to around .035. If the cylinder pressure is all over the place, you'll have to investigate further. But if the compression is fairly even then you'll have to go
back to the bleeds, with a different test (see test#2), which will tell you if you need to take the carb apart.
ALL OF THIS ASSUMES;
1) that ALL the air that the engine is getting, is coming in thru the airhorn, and
2) that the PCV and it's plumbing is working properly, and
3) that the fuel is reasonably fresh, clean, is Not contaminated, and
4) that the fuel level in the carb is correct and stable, and the mixture screws correctly adjusted ( about 2.5 turns out)
5) the engine is up to temp (about 185 or better), and
6) the idlespeed has been realistically set,(say 650/700 in N/P) and
7) the daymn choke is off; badaboom!
8) that's all
Test#1
The Idle airbleeds are under the choke plate. The easiest way to clear them out is this;
1) From under the hood, rev the engine up to about 1800/2000 rpm, and keep it there
2) slam the choke closed until the rpm comes down to 800 or so, then open that choke-plate
3) when the engine cleans out and the revs start climbing, release the throttle
4) go see if it's any better
5) repeat as necessary, but not more than three or four times at most.
6) this action will suck a huge amount of fuel out of the bowl thru every exit point, including the bleeds, attempting to flood the engine.
Test #2
1) go find your idle mixture screws.
2) counting the turns, screw them all the way in gently seating them. Do not force them. Write the numbers down.
3) then back them right out, being careful to not lose the springs. Put them somewhere safe.
4) send a gentle puff of air into the circuit, or a good shot of any aerosol lube or cleaner. That circuit goes four or five places, namely; the hole you are puffin, the air bleeds, the idle-discharge ports, the transfer-slots, and back up into the idlewell. The idlewell may or may not come from the mainwell, I don't remember. The point is the same, in as much as whatever pressure device you use, has to produce a strong enough blast to clean out all those passages, especially the airbleeds, which you can witness by looking under the choke plate. However, you can't just blast 120psi into there and expect the floats to live. So you gotta use short intermittent puffs, allowing the pressure in the float chambers a second to relax, between puffs. When/if you go looking down into the carb, you outta be wearing eye-protection, cuz some cleaners will burn your eyeballs.
