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Re: SU lean/rich confussion

Subject: Re: SU lean/rich confussion
From: Kevin Sullivan <>
Date: Thu, 21 Dec 1995 11:53:47 -0600 (CST)
On Thu, 21 Dec 1995 wrote:
> Using the colortune I find that I have an excessively rich (yellow combustion
> color) mixture in all cylinders which hardly changes at all with jet
> adjustment.  I can even have the jets cranked all the way up flush with the
> base and the colortune still shows very rich combustion.  I've checked and
> doublechecked the usual things:  needle shoulders are flush with the piston
> surface, jets are centered, pistions don't stick, float chambers are not
> flooding, float needles are new, and I'm pretty sure I have the float levels
> set correctly at about 1/8th inch.
> Other things like timing, point gap/dwell, valve lash, are adjusted and seem
> to be fine.
> How can I have a funky idle with air leaks and an uncontrolably rich mixture
> at the same time!?!  The DPO seems to have been satisfied with a very erratic
> 1400-1800RPM idle, since it runs great as long as you're accelerating.  I'm
> beggining to wish I was satisfied with it also, as it's ruining my holiday
> spirit!  Any help would be greatly appreciated.

Been there.  The colourtune doesn't actually tell you the mixture.  It 
just shows you one view of the flame.  I had old, high resistance plug 
wires and the colourtune showed "rich" even when the carbs were so leaned 
out you couldn't drive it.  Once I got the new wires on the mixture 
adjusted by ear (lift the piston) easily.  Colortune is interesting but I 
don't need it and wish I'd saved the money.  I will be spending some 
soon.  Baby wants an engine rebuild for Christmas.

Anyway, back to your problem.  Bad coil, cap, rotor, wires, or plugs 
(well, the colourtune _is_ your plug in this case) will give you a poorer 
"yellow" burn.  Make sure you're getting good spark.

Kevin Sullivan -- 1960 MGA
Nichols Research Corp.
Shalimar FL USA

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