Aisan Carb Installed - How to tune it properly? (1 Viewer)

[Neil826]

Hi, have just installed an aisan carby on my 3f, the previous owner had a holley on it.
It just wont idle right. I have got it to the stage where it wont stall but the idle mixture screw is about 4 turns out and it smells like its running rich. Idle fluctuates from 600 - 1200 rpm and has a misfire.
I have all the vacuum ports plugged except for the choke breaker and dizzy advance. The fuel is half way up the bowl window. Fuel cut solenoid is working.
I gave it a quick thrash around the block and it seemed to run good. No hesitation and good acceleration.

Photo of carby



I have tired the method described in the fsm of adjusting the mixture for the highest rpm, then setting the rpm with the idle speed screw but i still cant get it right.

Any suggestions?

 

[Pin_Head]

You can't smell running rich because it produces carbon monoxide. If you smell fuel, it is either from misfiring or a leak.


Won't idle problems are often due to manifold vacuum leaks and there are lots of places to leak.

If the idle mixture screw has no effect and your idle fuel solenoid is working, it is likely you have a vacuum leak.

People often compensate for a vacuum leak by upping the idle speed screw so that it will run off the main jet. If so, you can see fuel dribbling out of the main jet at "idle".

 

[gregnash]

So you are saying you did the lean drop method from the FSM? From what JimC has stated, the lean drop method shows that 2 turns out from bottom on the fuel mix screw is the starting point with 4 being about normal for a desmogged engine. Not familiar with the 3F carbed version so cant really comment on what should and shouldnt be plugged.

 

[Delancy]

Not familiar with the 3F carbed version so cant really comment on what should and shouldnt be plugged.

3F carb is, essentially, a 2F carb with no emissions implications, for what that's worth.

 

[Neil826]

Spent about half a hour today trying to find vacuum leaks with a lpg torch. Found nothing until I pulled of the the distributor advance to replace the vacuum line. I had put it on the charcoal canister port by mistake
I then was able to set the idle mixture and speed properly.

Is there supposed to be a gasket or something between the carburetor and intake pipe that sits atop it? The motor wont stall when I block the intake.

 

[SmartyPants]

Yes there should be a rubber gasket between carb and air cleaner.