New Carb and PCV valve

[Chuck Dyck]

I just bought a new carb and will be installing it this week.
I have the PCV kit installed already. Will the mixture setting on the new carb be good or will I have to reset it?
Chuck

[Antibes]

You will need to reset it. IIRC the starting point is 3/4 turns out. Then adjust from there

[Chuck Dyck]

Originally Posted by Antibes

You will need to reset it. IIRC the starting point is 3/4 turns out. Then adjust from there

I want to make sure I will be doing this right.
Warm up the engine.
Put it under load.
Set it to cruising RPM.
Turn the mixture screw to get max RPM.
Reset the idle.

Is this the complete procedure?
Chuck

[dvd]

Chuck just set it 3/4/turn out, get it started and adjust it until she runs smooth. Its real easy. I too was concerned about turning carb adjusting screws as I had never had anything good come from it. But the a-4 carb adjustment is easy and you will want to adjust couple of times a year just to make sure she running her best.

DVD

[romantic comedy]

I set the mixture at idle, as that is what it is for.

Adjusting it at high speed will not be the correct setting for idle.

[Chuck Dyck]

Thanks
I am off to the lake tomorrow to give it a shot.
Chuck

[Dave Neptune]

Chuck, re your new carb, if it is equipped with the adjustable jet (and add on) you will need to do a hi-speed adjust. If not all you need to do is set the idle.

To set the idle START with the "idle air mixture screw" with the spring on it. Turn it in gently until it is on it's seat, then open approximately 1/2 turn to get started. Start the engine and let it warm for a bit at hi-idle or working a bit on the dock lines until warm. then slowly bring the throttle back to it's stop. This is the idle speed screw the throttle rests against. Now you are ready to adjust the idle. Turn the speed screw to get around 7~800 RPM's and listen. With the engine at idle you can now start the idle mixture adjusting. Slowly begin to turn the mixture screw out(leaner more air) until the engine begins to stumble a bit or get rough, once there let it run a few seconds and begin to turn the screw back in to richen until the engine runs smooth. Now while doing this the engine idle speed can change so you'll need to reset the idle speed and then recheck the mix again. Repeat until the idle is smooth and slow at around 700 is fine.

Dave Neptune

[Chuck Dyck]

Thanks Dave that is just what I need.
Chuck

[roadnsky]

Chuck-
Just a few pics to for examples of Dave's procedures.

[Ball Racing]

That carb is just TOO Clean!!!

[Dave Neptune]

I'm not so sure Daniel I do see a few nicks on the idle stop screw.


Dave Neptune

[roadnsky]

Oh Puullleeeaze!

[Chuck Dyck]

Thanks for all the help, the carb is in and I ran through the idle mix procedure but I can't get the idle less than 900.
Checked the linkage and the choke, they are good.
Could it be the new premium fuel I am using, 91 octane, the only fuel around here without ethanol?
Or, is it possible my timing is out?

[ndutton]

Two thoughts:

• Did you screw out the idle speed (not mix) adjustment screw so it clears the stop?
• Try adjusting the idle with the PCV port on the manifold spacer above the carburetor closed off.

[Chuck Dyck]

I backed the idle screw completely off. But have not blocked the PCV valve. If it is the PCV is it something I will have to live with?

[ndutton]

Let's see if it makes a difference first but if it does I'll leave the adjustment advice to those who have a PCV system and have been able to finesse the idle. My opinion is certainly in the minority but I am not a fan of a PCV system on a carbureted engine and depending on your results you may be describing exactly why I'm not a fan.

Your idle adjustment difficulty may well be a manifold vacuum leak and I have argued for years that a PCV system is in fact an intentionally designed vacuum leak so to me your symptom falls right in line.

[Chuck Dyck]

I will give it a try when I am at the boat this week.
Thanks
Chuck

[Sony2000]

I have a slightly different way to do the adjustment.
With the idle speed screw set not to touch the carb, throttle back, and the engine running, you begin to lean out the carb mixture screw. (counter clockwise). The engine is idling very slowly until the leaning will cause it to run rough. At this point screw in a 1/4 turn to get back your smooth idle.
Now screw in the idle speed screw, (raising the RPMs) to a point that the engine will go into gear and not stall. Or advance the throttle a little for higher RPM, and then set the speed screw to touch the carb body.

[hanleyclifford]

Originally Posted by Chuck Dyck

Thanks for all the help, the carb is in and I ran through the idle mix procedure but I can't get the idle less than 900.
Checked the linkage and the choke, they are good.
Could it be the new premium fuel I am using, 91 octane, the only fuel around here without ethanol?
Or, is it possible my timing is out?

Carburetor adjustment is actually the last item on the tune up procedure. First the timing and dwell must be on spec. Ref the PCV; if you mount the valve vertically you will have better results. Neil is right about the thing being an engineered vacuum leak. Under no circumstances should the thing be mounted in such a way that solid oil can get thru the valve into the airstream. The valve should be functioning in such a way that it allows the minimum passage consistent with holding a slightly negative pressure in the crankcase.