Choke/mixture screws

[waterdawg69]

How do you adjust the lean/rich choke/ and the two air mixture screws at the bottom of the carb? is a rochester 2bbl thanks for any advice.

 

[Blk-n-Blu]

Re: Choke/mixture screws

Dwayne, Was just cruisin the net and found this help site. maybe it will help you
http://www.sterndrives.com/carburetor_type.html

 

[waterdawg69]

Re: Choke/mixture screws

thanks Blk-n-Blu : it elp a little but how do is adjust the mixture screws on the bottom of the cab. thanks for the help

 

[freddyray21]

Re: Choke/mixture screws

the choke is adjusted once the motor warms up. I don't know the year on your's but if it's like mine there is a large black control for adjusting the lean rich mixture. After the motor is warm loosen the three screw and turn the black section until the choke is fully open. On the mixture screws I run them all the way in slowly to not forcefully bottom them out. I open them about 1.5 turns start the motor them move them in or out in synch as needed until it idles smoothly. Don't know if its the right way, but it's what I do.

 

[waterdawg69]

Re: Choke/mixture screws

Thanks freddy, its a 160 hp mercrusier 4.1 liter

 

[Blk-n-Blu]

Re: Choke/mixture screws

I know someone will chime in here, but the use of a vacuum gauge helps when setting up the carb. Been looking for days for the rochester 2bbl set up procedure.
To add to what freddy said, when engine is cold, one push of the throttle to the forward position should allow the choke plate to close almost all the way. as the engine warms up to operating temp the plate should open all the way. I would not touch the screws just yet. but if im too late for that the initial 1.5 turns from seated should put you close. Do not tighten the screws into the seats.

 

[waterdawg69]

Re: Choke/mixture screws

thanks blk-n-blu i have a problem with it dieing when put into foward gear fast it hesitates first. and someone tells me its either the choke setting or the air mixture screws. i had the carb rebuilt. but it still seems to do it, then someone told me the accelerator pump. so i had the carb re-checked and still does it. so im trying to do the process of elemination. thanks for the help

 

[calwldlif]

Re: Choke/mixture screws

A vacuum gage and a tach are benneficial
to setting air/fuel mixture(Idle)
First a proper tune-up to include at least dwell/timing
Full operating temp/choke off.
Usual adjust is maximize rpm/vacuum at engine
spec idle rpm. continue adjusting idle stop (to rpm spec) as mixture screw is adjusted. final setting is usually
50 rpm drop from a enrichening(smog leaning)
final air screw setting. adjust idle stop back up 50
done.
The problem you have?
stalls when putting in gear?
This has nothing to do with accel pump.
Please retell problem with out to much
side issues

 

[Silvertip]

Re: Choke/mixture screws

1. Don't even think about choke setting on a Rochester 2bbl with a warm or hot engine. Chokes are a cold engine function -- makes no sense to try and set it hot.
2. Open the throttle about half way. The choke plate should close. Move the plate by hand to make sure it functions freely. If not, fix the problem. Shafts and plates can bind due to casting warpage by over enthusiastic wrenches.
3. Loosen the three choke disk adjustment screws.
4. While holding the throttle about half open, rotate the disk so the choke opens -- then rotate it back so the choke just closes. If the choke does not respond to these movements, the spring behind the disk is disconnected or not functional or the choke itself is binding.
4. Tighten the three screws.
5. Start the engine. The vacuum break should pull the choke open slightly when the engine starts. If not, the vacuum break/pull-off needs attention.
6. As the engine begins to warm, the electric function of the choke will steadily open the choke. If the choke does not open fully or not at all, the heater is probably bad or voltage to the choke is not present.

 

[freddyray21]

Re: Choke/mixture screws

don't have the electric function on my choke. that is why i said if if is like mine. Mine has a heat tube coming from the intake that activates the choke to pull it open. on mine you will never be able to tell if it is fully open unless you start the motor and let it warm up.