rough idle

recent restoration on 52 styled B with wico XB distributor. rebuilt carb and distributor, valve tappets adjusted to .020. Can not get it to idle smooth and the governor hunts a very little. What am I doing wrong or not doing?

Carb not throughly cleaned. Might have some plugged passages if you didn't remove all the brass plugs and run drill bits through them, or try opening the idle adjustment needle more. That Wico XB distributer isn't very reliable either.

(quoted from post at 11:07:35 11/28/14) Carb not throughly cleaned. Might have some plugged passages if you didn't remove all the brass plugs and run drill bits through them, or try opening the idle adjustment needle more. That Wico XB distributer isn't very reliable either.

Click to expand...

Make sure the throttle linkages aren't binding or rubbing on anything either.

Carb was disassembled soaked in cleaner and all passage ways were blown out with compressed air
. Replaced main jet and all new brass plugs. Would the timing advance in the wico distributor cause the idle problem if it was not operating properly?

Blowing out with compressed air won't clean those small passages.

There is no timing advance in the mag.

Oops disregard

Well you've answered your own question- use drill bits of the
proper size, aircraft ones so they're long enough, including the
secret passage, or have what you got. It is virtually impossible
to get clean any other way.

What is the secret passage?

If it is idle passages and/or ports plugged you should be able to slowly close choke slightly and it should even out as it will cause it to start getting fuel from main load nozzle. There are 5 things that have to be right to idle perfectly. First is the idle passages, both fuel and air bleed, must be cleaned/drilled , 2nd the little needle sized ports in bore at throttle plate need to be open, 3rd the throttle plate needs to be perfectly round and not worn at top and bottom from vibration, 4th the throttle shaft bushings need to be snug (no play at any rotational setting) you may need to replace shaft also as it is usually worn also and 5th and you don't hear this being done much but usually NEEDS done. The throttle blade wears a trough in the bottom of the throttle bore from years of vibration. Usually at the idle position. With everything else new it will STILL leak air at this spot. If it can suck air anywhere it will NOT suck fuel from the idle ports in correct amount to idle correctly. Sand blast the inside bore around throttle shaft / blade wear trough and use epoxy/jb weld to fill this trough in. Once cured, wrap sand paper around a large deep socket and use this to sand it flat. Use 80 grit to get it 90% and 180 or finer to get smooth finish the last 10%. Maybe a little bit by using fingers only. Then make sure when you push the bushings in that you push them all the way to flush with inside of bore and then 1/16 more so the actually protrude into the bore enough so you can use your die grinder to shape the squared off end perfectly to the curvature of the inside carb contour. Close throttle completely with blade in shaft loose so it will perfectly center itself and hold it there when tightning screws then work it open/shut to make sure it fits perfectly without sticking shut. Now the blade will NOT wear on your repair epoxy because it will sit perfectly on the brass bushing itself and when shut, it has nowhere else to suck but through the idle port where it needs to. Make your mechanical/needle adjustments and it should idle better than new. (they didn't push them bushings in far enough when new)

(reply to post at 10:40:20 11/29/14)

Click to expand...

When the choke is slightly closed the idle is very smooth. I will follow your instructions to the letter. Thank you for solving my problem.

Should have said to do the bushings first before the epoxy (if needed) so you don't screw up your epoxy job while doing the bushing ends. Post back when you get it done as to how she runs/idles. Thanxs.

It's behind the brass drill plug down in the side of the stem towards the bottom. Once plug is out, use drill bit by hand to make sure passage is clean all the way into second little chamber. You should be able to insert your small bit down from the top drill plug hole and see the end of it moving down in that bottom one. My e-mail is open if any more questions.

Here is a pic. That tiny hole you see is where the idle needle lets fuel into idle gallery. It goes up past the needle slightly and then turns and goes horizontally towards that drill plug (that horizontal passage is the secret passage)it's about 1/4" long and dumps into the verticle passage going up . If you take out the drill plug, you should be able to see your idle needle straight ahead. If not then the passage is plugged with rust. Use the correct drill or you may be able to use a metal pick to open it up.

(quoted from post at 17:35:51 11/30/14) Here is a pic. That tiny hole you see is where the idle needle lets fuel into idle gallery. It goes up past the needle slightly and then turns and goes horizontally towards that drill plug (that horizontal passage is the secret passage)it's about 1/4" long and dumps into the verticle passage going up . If you take out the drill plug, you should be able to see your idle needle straight ahead. If not then the passage is plugged with rust. Use the correct drill or you may be able to use a metal pick to open it up.

Click to expand...

Thanks for all your help and information. Its is much more than expected.

(quoted from post at 13:49:52 11/30/14) It's behind the brass drill plug down in the side of the stem towards the bottom. Once plug is out, use drill bit by hand to make sure passage is clean all the way into second little chamber. You should be able to insert your small bit down from the top drill plug hole and see the end of it moving down in that bottom one. My e-mail is open if any more questions.

Click to expand...

url]


Finally received the necessary parts to overhaul the carb per your instructions.. The idle is very good, like factory new. Thank you very much for all the help.[/url]