i learned backwards (carb tune-up)

[Anonymous]

i know how to rebuild a motor, pull and drop one, and all other maintenance. but i never did learn how to tune a carb. i've got a carter YF. is it something along the lines of tighten some screw all the way down and back out a 1/4 till she runs right?

thanks for any help. pulled one of the plugs while waiting for tranny parts, and she is all kinds of fouled. carbon deposits. and running rich. by the nose meter, and by reading the plugs. thanks for any help.

 

[pedal2themetal45]

HI TCS64I6
The fould pulgs could be the results of a bad power Valve or a bad Air/fule mixture..
If I remember right the number of the power valve should be 1/2 of the Vacuum at idle. Not sure where it is on your carb..
As for setting the carb mixture it goes..
If you have not rebuilt the carb then I would get some spray carb cleaner and remove the screw that is in the base plate of the carb. First screw the screw all the way in GENTLY not hard and count the turns this well give you a setting point. Then secrew it out all the way and spray carb cleaner in the hole, this well clean it out of varnish and such. Put the screw back in and screw it all the way in GENTLY then turn it out the number of times you counted previously.
Start the car then spray cleaner down the throte of the carb while it is running, it well want to die so fether the throtal to keep it running. After that set the idle with idel screw then turn the mixture screw (the one in the base of the carb) in or out to acheve the best (smoothest) idle. Rest idel screw to the specific idle of your car (650/700). Then repeat to make sure it is right. A SMALL AMOUNT GOES A LONG WAY WITH THE MIXTURE SCREW. I would turn it 1/8 or 1/4 turn at a time. The finaly for a lean drop I would turn the mixture screw in just enough to get about a 25 rpm drop in idle.
That should do it.
Tim

 

[Anonymous]

the mixture screw however only affects the carb at idle and initial response. screw in slowly till it stumbles a little then out till it stumbles a little then find the middle for everyday driving ,a little farther in for ecocomy a little out for power. For midrange through top end changing of jets is required for overcoming lean/rich problems. Start finding some literature on basic carb tuning and study up -tuning these little 1BBl's is easy but finding literature could be a little difficult--good luck. Once you get past your initial hesitation it is really fairly simple. I can rejet a Harley carb in 5-10 minutes -all three circuits-NOW -was a time i would take an afternoon for this. I am a strong believer in AFM gauges as you can get a real time knowledge of your fuel activities. This is overkill on a stock set-up however.a sticky choke,a weak spark or dirty filter will cause the same symptoms.