Fuel/Air Mixture

[Buckner99]

1984 720 Smells like it is running rich and smoking. Was wondering if anyone had an idea of how many turns out the fuel air screw needs to be on a stock carb. also where to buy a weber or better carb for this thing. thanks

[datzenmike]

The idle mixture screws adjusts only the idle mixture. It does nothing for above idle. Are you saying it seems rich all the time or only at idle? FYI the '84 idle mixture screw is set and sealed at the factory so.... unlikely this is the problem.

 

Smoking? At idle or driving or both?

White, black or blue smoke?

[Buckner99]

that confuses me because on my carb I have to screws. the idle screw and another farther towards the firewall thats hard to get too. it smells rich when its warming up. just regular white smoke/steam like a cold vehicle would do. if you could inform me of what the other screw is for that would be great. i can take a picture of it tomorrow.

[datzenmike]

The idle speed screw increases and decreases the idle speed.

 

This is the idle mixture screw with the sealing plug removed...

 

 

 

Unlike EFI engines, carburetors have a choke that makes the engine run rich during the warm up period. It will be very normal to smell unburnt gas when the choke is on. After about 8-10 minutes the choke shuts itself off. You could check you choke to make sure it's shutting off by simply lifting the top off the air filter and looking at the choke flap.

 

Choke closed engine cold...

 

Choke open, engine warmed up...

 

[Stinky]

You are probably best off to leave it alone.  If you still want to fool w/that screw...

 

Get it HOT (w/the temp needle in the operating zone), choke OPEN.

 

Screw it in and count the turns and then put it back where it was.  Motor running....turn it in till it dies.  RE-set to center, Motor Running.... turn it out till it dies...then put it in the middle.

 

OR, use a vacuum gage and set it to the highest idle and highest vacuum.  (the best way).

 

 

[Buckner99]

10 hours ago, datzenmike said:

The idle speed screw increases and decreases the idle speed.

 

This is the idle mixture screw with the sealing plug removed...

 

 

 

Unlike EFI engines, carburetors have a choke that makes the engine run rich during the warm up period. It will be very normal to smell unburnt gas when the choke is on. After about 8-10 minutes the choke shuts itself off. You could check you choke to make sure it's shutting off by simply lifting the top off the air filter and looking at the choke flap.

 

Choke closed engine cold...

 

Choke open, engine warmed up...

 

Ya my carb doesn’t look like that. I’ll have to take some pictures. 

[bottomwatcher]

If it is running fine but stinky your catalytic converter is probably shot. If it is original it is shot. I am running a fuel injected KA no cat. It stinks! 

[datzenmike]

If the carburetor is set and running right it shouldn't stink, certainly not of unburnt gas.

[Buckner99]

here’s a picture of my carb. Engine off.

[datzenmike]

4 hours ago, Buckner99 said:

Ya my carb doesn’t look like that. I’ll have to take some pictures. 

 

 

Uh yeah it does. Is the engine warmed up or not.

 

 

 

 This is a ceramic heater to warm the air on a cold start. It will run without it.

 

 

 

This is the idle speed screw not to be confused with the idle mixture screw in my picture

 

 

[Buckner99]

So what are the two screws that I have circled? Cause the one on the right adjusts the idle when I turn it.. 

[datzenmike]

The unknown don't worry about. The one marked by you as the idle adjuster is as I said called the idle speed screw. Call it the idle speed because there is a second screw that also adjusts the idle called the idle mixture screw.

 

In my picture it's the Philips screw with the spring under it

[Buckner99]

Okay

[Buckner99]

The one I circled and the one in your picture is the same screw. 

[Buckner99]