Glad to hear that made such a difference!

Getting the idle mixture right won't necessarily fix mid-range or full-throttle problems, but will affect idle of course, and low-speed/part-throttle cruising to some extent.

If you have modified your engine with extractors/headers, carb, cam, etc. you probably need to change the jets in the carb ... it may feel "powerful", but chances are you can make it run even better (and get better fuel economy) by tuning it ... that's a whole 'nother subject.

Well, I got that sucker tuned. Wow, what a difference! This thing runs like a raped ape. Got a little power increase too. Thanx guys

Wow, I knew there was a reason that I keep coming back to this site. That was some serious information dd. I really appreciate it. Well, I've been meaning to replace all those old vacuum lines anyway, so I guess I've got my project for tomorrow. Needless to say, I printed that last post and it will find a place next to my tool box. Thanx again for the info.:)

This is for regular carburetors. Backing it off 2 turns or so is a good "base" measure just to get the car started.

To make it run right, you can easily adjust idle mixture by ear:

- Make sure engine is fully warm, and the choke is fully open (shine a flashlight down the carby if necessary to see)
- Turn the screw half turn at a time in (clockwise)
- When you hear the engine slow down, back it out half turn until you hear it speed up (listen carefully)
Do this several times until you get the feel for it. Turn it too far in, you're leaning it out and will eventually stop the engine.
When you turn it out, you are richening the mixture, and it will start to run "rough" and kinda blubbery (hard to describe, but try it)
If you kill the engine, back the screw out again and start it back up
- Once you figure the point where turning it just begins to slow down, turn it in 1/4 turn at a time to fine tune it
- Continue this until the engine is running at the fastest, smoothest setting as far in as the screw will go. For best power, you can leave it here ... but ...
- For best economy and emissions, turn the screw in about 1/8 of a turn more. You'll hear the engine slow down just a little bit. This is the factory setting.

This will work well based on a couple of important foundations:

1. Set the points exactly (new points with a feeler gauge, used points need a dwell meter)
2. After dwell is correctly set, you can time the engine carefully. Use a timing light is best ... check any book for process or ask here for more information
3. Make sure all vacuum hoses are tight and there are no leaks -- these will affect idle mixture and running mixture. Notorious leaks are in old vacuum housings on the air cleaner (the bimetal is supposed to leak a little, but not the round flap valve servo). and all the round vacuum actuators on the carb itself. Better to plug a hose with a screw than to let it leak.
4. When the above is right, set idle speed: 650-700 rpm for a stock or mild camshaft. Do this before setting the idle mixture.

right on bro. good luck at the track, and let me know how that extra rad works out.

I'm off to the Kart races for the weekend at Summit Point Raceway in Charlestown, WV.

I had to put an extra radiator onto one of the Karts in front of the rear wing to help keep it cooler. It has been overheating every time it has been out and maybe this will do the trick. This is my nephew's Kart and he doesn't fully understand the theories of mechanics. I say that changing to a cooler range of spark plugs will bring down the temperature but he doesn't see how that could have any effects on water temperatures. I also think he jets the two Dellorto carbs too lean. The Kart has two radiators on it, one in the left side pod in front of the motor and one behind the driver. This Kart is the highest engineered Kart in the world and the most beautiful. It has been radared at over 170 MPH in 1988. It has a 96HP 250cc twin cylinder Rotax engine. I will post some photos of it next week as I hope to get pics of it this weekend. I'll post again on Monday as to the results of the weekend.

He also has another 250 Kart that he has the track record with at Summit Point Raceway.

Keep them Dattos between the ditches.

Mareo

thanks mareo, I'm gonna check that throttle shaft right now...

The best way to set the idle mixture is to use a vacuum guage and set the screw to as much vacuum as you can get. If you have no guage, I usually turn the screw in all the way and then turn it out about 1 1/2 turns. If it still runs like crap, there is something else wrong. Try shaking the throttle shaft. If it has lay, it is worn and there is no fix for that. I had to get a new carb. I screwed up and bought a Holly/Weber set up for the A14 but it is a screwy carb and I do not recomend them.
Mareo

does anyone know a good base mixture setting for air and fuel on an A-12 carb? Someone told me to run the screws all the way in, then back them off 2 1/2 turns. My car runs like crap at this setting. Any info is appreciated. thanx