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Old 12-20-2005, 01:19 PM
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Rzeppa Rzeppa is offline
Cruise Moab Chairman
Join Date: Aug 2005
Location: Kittredge CO, USA
Posts: 6,716

I've used the vacuum method, it works okay. As noted in Ken's post, make sure you've dealt with any vacuum leaks first, always work on it at proper operating temperature, and tweak your timing first. Another method I use is:

(1) Screw mixture all the way in. Then back it out 1.5 turns.
(2) Start truck. Increase idle adjust if it won't stay running.
(3) Back out (richen) mixture and listen to RPMs increase. When they don't increase any more, you're there. If you feel like it, go one more half turn to compensate for not having the air cleaner on. I really don't think it makes that much difference in the real world.
(4) Turn idle back down.

Note that the 2 barrel Aisan carb has a "choke breaker". As soon as the truck starts and a vacuum is made, the vacuum actuates a diaphragm which opens the choke just enough to allow some air in. So when you do adjust your choke, you don't have to worry about leaving a gap when the choke is closed. Also note that there is a separate, fast idle adjustment which is only active when the choke is closed. Like the regular idle adjustment, it's on the linkage behind the carb. I know there's a factory spec for the RPM, but just tweak it until it runs good when it's cold, and not doing anything when the choke is open.

Emissions notes: If you're too lean, you won't pass emissions due to "lean misfire". Turning the idle up above spec will help get you lower numbers. While running more advance than factory spec. 7 BTDC will normally get you better power and mileage, for emissions you want to retard it back to spec. No idea why, but you get better numbers, even though power and mileage suck. You can always put everything back after you've passed.
Jeff Zepp
Kittredge CO USA
1971 & 1976 FJ40s, 1978 FJ45, 1987 FJ60
Rising Sun 4WD Club, TLCA #4063
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