jimbo74

ok not sure if this is the right spot to post thins or not, so if it isnt, can a mod move it?


i have an 85 22r with a stock carb.... there are 3 tuning screws on the carb... there is the lowest one that i think is the mixture control... where should this one be placed at as a baseline.... like 3 turns out from being bottomed out in the hole, or what?

kyle_22r

here's the one i see a lot on 4x4wire:



i *think* turning the screws in leans the mixture, turning them out richens it

jimbo74

the idle speed screw is what im talking about... whats the baseline point it should be adjsuted to? 3 turns in? or out? or what? the previous owner did some tuning that i was not pleased about and would like to jsut get it more reliable and get better fuel econmy, however the mileage i am getting now isnt too bad.....

kyle_22r

ideally you shouldn't ever have to touch that one. toyota even thought that, since you have to drill the plug out to get to it! i think the baseline is 3.5 turns out

jimbo74

thanks for the baseline... i will try and set it at that then retune it when i get a chance..... i know, it was drilled out... the guy i bought it from was a mechanic that i worked with before... i knew he did some shady car work though, so i dont really trust what he did to my truck before i got it....

mikedog

I hope you can get the mixture right come smog time. You got to watch out for the CA smog nazi's if you know what I mean.

A few years ago, a mechanic told me that you have to use a CO meter to adjust the mixture settings correctly. I don't know if that's true or not. However, I bet a WB O2 sensor would work.

I wonder if the stock mixture settings are set lean from the factory? You know... good for emissions, but bad for max performance.

3.5 turns from bottom sounds about right. Are you using the lean idle drop method to dial it in further?

jimbo74

what method would this be?

Yamaha+Toyota=Fun

Screwing something in on a carb usually makes it leaner (closing the needle valve), screwing out usally makes it richer (opening up the needle valve)

Just a FYI

Phssthpok

Not exactly sure about the Toyota carbs, but on my Musclecars when I went to fire up a freshly rebuilt carb, I would bottom out the mixture screw(s), and then back them off 2 1/2 turn as a base line. I would also set the fast idle screw a little on the fast side just to keep things running when it fires because I usually disable the choke at first. (trying to tune with the choke on is a pain)

Once the car is running, back out the screw(s) to richen the mixture untill the RPM's no longer climb. (you may have to reduce the fast idle screw to keep from racing the engine...try not to exceed 1500RPM). You will now be running 'fat' (rich).

Once the engine has reached full operating temp, turn the idle SPEED screw out (reduce RPM) untill you achieve the idle speed you want. Then turn the MIXTURE screw(s) in (leaning out the mixture). The RPM's should rise as the mixture is coming into tune. (remember, you were loading the engine with slightly too much fuel before)

Repeat this process (reduce engine speed, then lean out mixture) untill the RPM's drop (the engine stumbles) as you are reducing the mixture. At this point you will want to back out the mixture (richen) and bring it in again SLOWLY until you detect the exact point that the engine started to stumble. Then back it out 1/4 turn and it's set.

Now take it for a test drive. Do a couple of hard acceleration runs and listen for pinging (pre-detonation) If you hear pre-det, pull over and back out the screw another 1/8-1/4 turn to richen it up a touch. Repeat untill no pre-det is heard. THEN TURN IT OUT (richen) ANOTHER 1/8 TURN (pre-det actually occurs before you can hear it)

You now have a shade-tree mechanic's 'tune' on your carb. 90% of the time this will NOT pass emmissions, but it will get you close enough that a little twist of the mixture screw SHOULD get you through. (assuming all else is funtioning properly)

Phssthpok

Bumbity bump...

Didja git it figgered?

jimbo74

i dont know, i dont have a tach nor a timing light, so i guessed... my guess was i bumped up the timing a little bit and leaned it out, havent heard any pinging yet and am running 87 octane... so im a just leave it at that for now and see what happens

jimbo74

what is this adjustment?