From: tm@iscsc.com

Date: Tue Aug 28, 2001 4:45 am

Subject: Easy weber idle mix setting

The following assumes the carb airflows are synced, and the linkages

are adjusted right. Sync and linkage sync is important to get smooth

off-idle transition. My LP400S with the too big 45mm carbs pulls nice

from 800 RPM, so my clutch stays happy in stop and go traffic.

If the car runs, I do not consider number of turns. I do one at a

time while changing plugs. I remove the idle screw completely, clean

the tip and seat with spray carb cleaner, and start with 0 turns. I

do not want to start rich, really rich takes a long time to subside.

It'll run on the other 11. I put the gunson colortune in the plug

hole for that cylinder and:

Non emisions - open the mix screw until I see orange flame, the close

it until I see a gas flame whitish blue with no orange streaks.

Emmisions - open the mix screw until I see orange flame, note turns

count, close to obtain lean miss (blue with orange streaks, blue-

white, dimmer blue, violet, violet does not fire each time), note

turns count. I set the screw 40%-50% of the way from lean miss to

rich orange turns counts. I usually try a few times till I observe

the same turn counts. I consider turn counts as hours or between

hours (1/24 turn units). There should be no missing. Missing is

obviously visible, you see the skipped beats.

Setting idle mixes is easy when you can see the fire in the cylinder.

For those of you that weld, behavior is somewhat like a oxy-acetylene

torch flame.

I do investigate a barrel which behaves differently from others, is

unstable, or misses regardless of setting.

I often reset idle mixes during a plug change since it costs little

additional effort. If I do not remove the idle mix screws, I run them

way out, shut then till the cylinder dries out, and set. I do this to

release any debris in the seat.

You may be forced to resync airflows, since you will run the idle up

if the idle mixes were set imprecisely.

I have used the colortune to get 120 ppm HC and 0.8% CO at idle with

no cats on 4 DCNF's.

Additional notes on the color tune:

- I open the plug gap slightly with a jewelers screwdriver.

- I do not use a gasket, and put it in hand tight.

- I do not run the engine up much.

- I attach a 3/8" ID piece of heavy wall hose to the plastic hex

adapter which serves as a flexible driver to easily install and

remove, particularly on 2V cars.

- I work where I can make the room dark. Especially helpful for the

front cylinders on 2V cars.

- Thinwall socket won't engage plug? Look for loose washers in the

plug well.

Links:

http://www.piercemanifolds.com - weber parts

http://www.gunson.co.uk - Colortune Europe

http://www.aep.bigstep.com - Colortune US

http://groups.yahoo.com/group/lamborghini_info/message/5935 plus

followups - 2V plug tool

-- Torai Madjid

http://www.geocities.com/lamboguy/SpecialTools.html