Carbrator setings

[apephoto222]

with the carburetor:

Does anyone know how many turns of each screw/ knob will make it run like or near factory???

[toboggan]

I've always heard that you screw them all the way in, then a turn and a half out!

[evilone]

Have you checked the manuals under "technical documents"?

[devenex]

What model and year? Even the Sprees have variation depending on the year I think.

Yeah definitely get the manual from the forum too, always seems to come in handy

[apephoto222]

its a 1986 special. I havn't found any specs in the Manuel's

[devenex]

1 & 1/2 turns out

[apephoto222]

what about the other two screws. Theres the idle on the top. Something in the middle and at the very bottom its the drain bowl screw. Would the 1 1/2 be the idle and what would the other two be???

thanks

[Wheelman-111]

Greetings:

Are you tuning some sort of Honda scooter or a Weed Whacker? It helps the Phorum to know model/year. If it's an Elite, Aero or Spree:

Top is the throttle stop. It sticks out and has an exposed coil spring. Tighten to achieve a steady idle. Factory spec is 1800 RPM on Aero/AF 05E.

Middle is a mixture adjustment. There's a spring inside the carb casting. Some people think an o-ring and a tiny washer belong in there (on Sprees), too. Unscrewing admits more air = Lean. Clockwise restricts air = Rich. Depending on model and condition, it might be anything from 1 to 3 turns out, optimized by listening for idle speed changes. Start at 2 turns out and tune from there.

Bottom is drain screw. Tighten firmly or risk gasoline all over Mom's new coffee table. There's no spring but there is an o-ring in there that can rot out, replace as needed. I Teflon-taped the threads for good measure.

[jesse1234]

Middle is a mixture adjustment. There's a spring inside the carb casting. Some people think an o-ring and a tiny washer belong in there (on Sprees), too. Unscrewing admits more air = Lean. Clockwise restricts air = Rich.

how does this work for tuning compared to jetting?

[Wheelman-111]

Greetings:

Several "circuits" within the carb control its output. From the low volumes of mixture necessary to sustain Idle, through the midrange of engine RPM at part throttle, all the way to WOT, each circuit "hands off" primary responsibility for the mixture content to the next in line.

The mixture screw mainly controls the content of the mixture at idle and just above idle. The engine is sucking against a closed carb throat, very minute quantities of air require just tiny "sips" of fuel, which the pilot circuit can supply. A stumble off the line is a symptom of incorrect low speed jetting.

As the throttle slide opens the throat of the carb, the vacuum created by the piston downstream can access increasing volumes of air at a "lower vacuum" pressure. The needle taper determines the mixture according to the area of the main jet exposed as the needle moves out of it, adding (we hope) the correct amount of fuel to the incoming air.

At higher engine speeds and WOT, the main jet pretty much runs the show. The relative contribution of mixture entering the intake flow via the tiny pilot circuit is now negligible. Therefore you can't adjust the carb for anything above low-midrange unless you change main jet or alter the shape of the needle.

The pilot jet size in the Keihin PA 04 is fixed and all but impossible to replace without special tools and teams of trained Japanese snow monkeys. The Amal Arreche pilot jet screws in and so can be replaced with different sizes. There are probably different needles available for both carbs, but finding what to order - and from where - would be a trick.