The only thing that comes to my mind is that the engine is sucking more air
through the rear carb than the front but you said the balance was OK.....
You could try checking the position of the needles in the carb pistons; the
'shoulder' of the needle should be flush with the base of the piston.
Andy
>From: Jeff Boatright <jboatri@emory.edu>
>Reply-To: Jeff Boatright <jboatri@emory.edu>
>To: spridgets@autox.team.net
>Subject: rich and lean
>Date: Sat, 1 Jan 2000 13:11:47 -0500
>
>Dear Spridgeteers,
>
>I've recently noticed that upon initial acceleration, my engine
>(1275, dual 1.25" SUs) stumbles. Also, while sitting at idle, the
>engine seems to "load up", with the rpms becoming lower and erratic.
>Checking the carbs., I found that balance and idle were OK. I reset
>the mixture by screwing the jets upwards until they were both flush
>with the bridges, then down by two turns (12 flats). I attempted to
>fine tune using the method of slightly lifting the piston and looking
>for a change in rpm (a steady rise in rpm indicating too rich, an
>immediate drop indicating too lean, and a brief rise followed by a
>drop indicating just right). Doing this, I found that the front carb
>was about right at only 6 flats down from bridge and the rear carb
>was right at 15 flats down. This seems way off; typically these
>settings would have caused the front carb to be way too lean and the
>rear to be rich.
>
>Any thoughts on this? I've not encountered such different settings
>before. Also, the erratic idle rpm seems to come and go now, so it's
>not fixed entirely. Could this be a float bowl problem?
>
>Thanks in advance for any thoughts on this.
>
>Jeff
>Jeff Boatright __o_\__ '65 Austin-Healey Sprite
>http://userwww.service.emory.edu/~jboatri/sprite/sprite.html
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