Aisan Carb adjustments - Help! (1 Viewer)

[Horitexan]

Does anyone have an illustration, or picture, of a stock Aisan carb for a '75 FJ40 that shows what the different adjustment screws are for?

Also, can someone give me a step-by-step guide, or refer me to one, for tuning a Aisan carb? i just installed one in my cruiser and I'm having trouble getting it set just right. I was hoping to find some instructions, like an idiot's guide, to give me some help.

Nick

 

[Fast Eddy]

Also, can someone give me a step-by-step guide, or refer me to one, for tuning a Aisan carb? i just installed one in my cruiser and I'm having trouble getting it set just right. I was hoping to find some instructions, like an idiot's guide, to give me some help.

Get the FSM. It goes into great detail on tuning, etc. You'll need a vacuum gauge too.

 

[2mbb]

These pictures are from the SOR website. The first picture is a view of the side of the carb that is next to the valve cover. The brass screw at the base of the carb is the idle mixture screw. Turning the screw clockwise (in) leans out the mixture, turning the screw counterclockwise (out) make the mixture more rich.

The second picture is a view of the side of the carb that is next to the fire wall. There are two adjustment screws on this side. The lower screw is the idle speed screw. The higher screw that is partially hidden by the U shaped linkage is the fast idle speed screw (used when the choke is engaged). Turning these screws clockwise increases the speed.

This adjustment procedure is for the later 2 barrel carb, but it's probably ok. Warm the engine up. Screw the idle mixture in until it seats, then back it out two turns. Start the truck, choke off. adjust the idle speed screw until the idle speed is about 700 rpm.

Using a tachometer, adjust the idle mixture screw a little bit at a time in the direction that increase the rpm's. I usually turn the screw in 1/4 turn increments. let the engine adjust and compare the rpm to see if it's higher or lower. When further adjustment of the idle mixture screw does not increase rpm any more, reset the idle to 700 rpm using the idle speed screw. Repeat from the start of the paragraph until no further increase in rpm is achieved. Set your final idle speed using the idle speed screw.

x2 on the FSM.

 

[mr_manny]

a vacuum gauge is also a good visual aid when attached to manifold vacuum.

googled some links on the subject:
http://www.centuryperformance.com/vacuum.asp
http://www.edelbrock.com/automotive/eps_sect2.html

 

[Pin_Head]

Thbe vacuum advance connects to the brass tube in the base of the carb to the right of the idle mixture screw facing the valve cover on the left picture.

the "power valve" brass tube (marked #8) on the top of the carb facing the front gets connected to manifold vacuum. You can see it sticking out on the top right of the left picture.

HTH

 

[Horitexan]

Whoa! No wonder she's running pretty poorly, LOL! I TOTALLY screwed up the vaccuum lines when I converted back to the Aisan! I don't know if that's my whole problem, but I'm sure it aint helpin'!

What about the other 2 vacuum tubes- should they be capped off? If not, how should they be connected?

Is the wire that you see in the first picture the 'fuel solenoid'? Can I run it of an in-line 12v fuse connected to the battery, or is there a better way to connect it?

Thanks for all the info and support y'all- I don't know what I'd do without y'all!

Nick

 

[Pin_Head]

What "other two" vacuum lines?

The idle fuel cut off needs to be connected to the "engine" fuse circuit. This is a black wire with yellow stripe that also feeds the voltage regulator. It is not the same as the black wire with yellow stripe that goes to the coil.

 

[Degnol]

What "other two" vacuum lines?

.

I think he is talking about the choke pulloff and the one at the top of the airhorn


Ed

 

[Horitexan]

Degnol- Those are the two I was talking about. What do I do with those?

Pin_Head- Thanks for the info on hooking up the "Idle Fuel cutoff!"

 

[Degnol]

I don't know what the one at the top of the airhorn does, but I don't think there is a need to cap it. The choke pulloff hooks to full manifold vacuum, probably under the carb on the insulator/spacer.
GL

Ed

 

[Pin_Head]

The choke pull off gets manifold vacuum. The brass tube in air horn that faces forward is the power valve. It gets manifold vacuum too.

75s have an Aux Accelerator Pump, AAP, which is the curved brass tube that is on the lower right of the picture on left. I'm not sure what kind of vacuum runs it, but it will run fine without being hooked up.

 

[Fuzzy Logic]

The brass tube in air horn that faces forward is the power valve. It gets manifold vacuum too.

Mr. Head:
You say the port(circled in red) needs vacuum?? but, mine has a sucking sensation going on now, is this normal?

 

[Pin_Head]

There should be vacuum on the rubber hose that connects to the brass tube in the circle. When the hose is disconnected, there is no vacuum on the tube.

The tube operates the power valve.

 

[mountainman]

Time to highjack!! Can you just cap off the air horn tube? Mine runs fine with no rubber hose connected.Also,can you use the tube next to the idle mixture screw for vacuum advance? It looks like it's in the right place!

 

[badass]

Yes mine runs fine without it also, what is it supposed to be hooked up to?

 

[Pin_Head]

You can cap off the brass tube on the front of the air horn and your engine will run, but it will rich and get poor fuel economy. It is supposed to be hooked up to the VSV that is operated by the engine control computer, but if that system is missing, manifold vacuum will be adequate.

The vacuum fitting by the idle mixture screw show in in the picture is appropriate for running a vacuum advance distributor, but not all tubes in this vicinity are. The vacuum port needs to enter the primary bore just above the throttle plate and not below it. You can check by sticking a piece of nylon fishing line in the hole and taking a peek inside to see where it comes out.

 

[Ming89FJ62]

You'll find a #8 stamped into the upper carb body next to the nipple for the power valve. Doesn't the larger nipple on the upper carb body connect to the charcoal canister?

 

[mountainman]

Thanks for all the info guys!!

 

[Pin_Head]

You'll find a #8 stamped into the upper carb body next to the nipple for the power valve. Doesn't the larger nipple on the upper carb body connect to the charcoal canister?

The number for the power valve connection is different on different years. The larger curved tube is a bowl vent that is only of '78 and up carbs. You can cap this bowl vent tube without signficant effects.

 

[John Smith]

The number for the power valve connection is different on different years. The larger curved tube is a bowl vent that is only of '78 and up carbs. You can cap this bowl vent tube without signficant effects.

Pin_Head, Is there a power valve connection on a 79 carb that needs vacuum? That may explain my rich running conditon.