Chinese 34ADF Thread

[Jrlovvorn]

Thanks!

[Jrlovvorn]

Well, you guys nailed it.

I am indeed too lean. Plugs are white and dusty.

I have tuned a lot of old motorcycle carbs, but this thing is more complicated.

The mixture screw on the base of the carb facing the left fender and brake master, was turned out like 5 turns when I got it.

I should have counted. I turned it all the way in to gentle stop, then backed it out 1.5 turns.

(note - turning it all the way in did not kill the idle, which I think is a bad sign, and perhaps means I have an air leak somewhere else on the carb - ie, if its not getting enough air to idle from that screw, it must be getting it from somewhere else).

The car runs flawlessly, but after a 30 min drive with the mixture screw at 1.5 turns (rather than 5 turns out), I see no change in my white plugs.

I think this means I need bigger jets, but before I do that, can someone confirm the following?

1. Turning the mixture screw in is richer, and turning it out is leaner - ie, this is an air screw, and the further its out the more air. I have seen some that are backwards on old Honda bike, and don't want to chase my own tail.

2. There are no other adjustment screws on this carb that can enrich the mixture. Ie, new jets are the only solution.

3. White plugs are as serious a problem on a Fiat 2000 as they are on an air-cooled Honda 550. Ie, I cannot just ignore this problem and enjoy that the car is running awesome.

Thanks!

[vandor]

>1. Turning the mixture screw in is richer, and turning it out is leaner - ie, this is an air screw, and the further its out the more >air.

I am fairly sure that the screw controls the amount of fuel/air mixture entering the barrel from the idle fuel jet.

>2. There are no other adjustment screws on this carb that can enrich the mixture. Ie, new jets are the only solution.

No other adjustment screws. You may check the float level, if it is low it can cause a lean mixture.

>3. White plugs are as serious a problem on a Fiat 2000 as they are on an air-cooled Honda 550. Ie,

Maybe not as serious, but you do need to deal with it. Also remember that just bcs you drove the car 30 minutes, when you pull the plugs they will tell you the mixture during the last running condition, which was likely at idle.
To check the mixture during normal driving you need to switch the ignition off while driving and coast to a place where you can pull a plug to check mixture. Not easy to do it safely, so be careful that you don't lock the steering lock while the car is still moving!

[Jrlovvorn]

Thanks! That all makes sense.
A little harder to do a plug chop here than on a bike, and it's an automatic!
Will give it a try in a big parking lot.

[silvadw]

Hi, You may have read i finally installed a 34ADF and 1800 intake on by 79 2000. It goes well, when going but i have a couple of issues around idling. The diagram below shows a 32ADFA I borrowed from another post. I used this as a guide for my connections

I hooked up the canister top and breather connector to positions 8 and 1 respectively. The distributor advance is connected to 10. I had to have 10 inserted after the carb arrived by a carb shop. Is this the correct hookup also for 34ADF NOS?
Ports 8 and 1 have vacuum at idle but lose it upon opening the throttle
Issues
1) I can screw it in and the car dies about 1/2 turn from screw being seated. I can back out the mixture screw a lot (>4turns) without the idle being affected. Idle stays around 800-900 Idle screw is about 3/4 turn in after touching mechanism (I can get it low if I unscrew the idle speed screw) Is this leaky air? If i disconnect the breather connection, and block the port, the revs drop and car nearly stalls.
2) from idle, the car stumbles when i step on the gas quite badly. No backfire, no stalling. If throttle partially open, then floor the pedal, no stumble. Is it too rich or too lean at idle?
3) the water choke doesn't close when the car is cold unless I touch the choke flap. I can't see any binding on the linkages or the cable. it opens as i would expect. Same as my well operating but asthmatic 28/32 ADHA that i removed. Should i take the choke apart and check internally?
Thanks in advance for your help
Darrell

[vandor]

> 1) I can screw it in and the car dies about 1/2 turn from screw being seated.

Which screw?

> If i disconnect the breather connection, and block the port, the revs drop and car nearly stalls.

Is this with the air cleaner in place and the breather and crank vent hoses connected?

2) from idle, the car stumbles when i step on the gas quite badly.

Sound like it is too rich. If too lean, it would backfire into the intake.

3) the water choke doesn't close when the car is cold unless I touch the choke flap.

It won't close until you step on the gas. Ie. before starting the car cold, step on the gas, this activates the choke, and then start the car. Does it do that?

[silvadw]

Thanks Csaba,
clarification as follows
When car is warm
> 1) I can screw the mixture in and the car dies about 1/2 turn from screw being seated.

> If i disconnect the breather connection, and block the port, the revs drop and car nearly stalls.

Is this with the air cleaner in place and the breather and crank vent hoses connected? yes Idle speed scew is about 3/4 turn in

2) from idle, the car stumbles when i step on the gas quite badly.

Sound like it is too rich. If too lean, it would backfire into the intake. Ok i will try it about one turn out after seating

When car is cold, but air cleaner top removed so i can see what is happening -
3) the water choke doesn't close when the car is cold unless I touch the choke flap.

It won't close until you step on the gas. Ie. before starting the car cold, step on the gas, this activates the choke, and then start the car. Does it do that? No I have to remove the air cleaner and move it by hand. I am using the same technique which I used for the 28/32 ADHA. but flap is not closing. When i step on the accelerator and release 3 - 3 times the flap moves a little, perhaps 4mm. Maybe i will try holding the pedal down rather than just step and release. The carb is new as you know so maybe everything is a little bound internally

Any other advice gratefully received

[silvadw]

Ok so after travel i found time to address the carb issues... this was a new 34ADF
I removed the water housing from the choke. The mechanism of the stepped plate was not moving freely, and seemed to be dragging. I sprayed the bits with carb cleaner as I thought there may be dried oil/grease. After using the carb cleaner, everything moved quite well. I attached the water housing to make sure the choke plate opens properly when warming. After overnight I checked the plate closes as it should, and now it is all good. Only one press of the accelerator pedal, and the plate closes. Moral of the story, even "new stuff can have issues, especially if it sat around for a long time before using

Also I have fixed the rough idle. I tightened down the carb on the intake as the nuts were not that tight, and backed out the air mixture screw to about 3 ½ turns. I guess I need a larger idle jet, but will worry about that in due course.

Hope this helps others

[fiat218]

>1. Turning the mixture screw in is richer, and turning it out is leaner - ie, this is an air screw, and the further its out the more >air.

I am fairly sure that the screw controls the amount of fuel/air mixture entering the barrel from the idle fuel jet.

>2. There are no other adjustment screws on this carb that can enrich the mixture. Ie, new jets are the only solution.

No other adjustment screws. You may check the float level, if it is low it can cause a lean mixture.

>3. White plugs are as serious a problem on a Fiat 2000 as they are on an air-cooled Honda 550. Ie,

Maybe not as serious, but you do need to deal with it. Also remember that just bcs you drove the car 30 minutes, when you pull the plugs they will tell you the mixture during the last running condition, which was likely at idle.
To check the mixture during normal driving you need to switch the ignition off while driving and coast to a place where you can pull a plug to check mixture. Not easy to do it safely, so be careful that you don't lock the steering lock while the car is still moving!

why cant you just pull over and stop the car then kill the engine?