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TR3A SU Carb - Mixture too rich

To: triumphs@autox.team.net
Subject: TR3A SU Carb - Mixture too rich
From: Mike Sanford <Mike.Sanford@comcast.net>
Date: Mon, 08 Sep 2003 09:21:56 -0500
I purchased a '58 TR3A that has been "restored" and have been having 
trouble getting the fuel mixture correct. It runs rich as identified by the 
carbon sooted plugs and the use of a Gunson Colortune. After checking fuel 
filter, fuel pressure, floats, ignition/timing, etc., I decided to dig into 
the SU's. The mixture adjusting nuts were set completely up (tightened) as 
far as they would go, so there's no way to make it run any more lean by 
changing these. I've also found some things that don't match the Haynes SU 
carb book or other notes that I have found online.

The book states that when the adjusting nut is screwed up as far as it will 
go, that the jet will be protruding into the bore. This is not the case on 
mine. With the adjusting nut all the way up, the upper jet bearing is just 
under (about 1/16") the level of the bridge and the jet is about 1/16" 
below the top of the upper bearing.

Also, the needles are marked "369". I can't find any reference to this 
specific needle marking.

Does the fitting of the upper jet bearing and jet sound correct? Could the 
needles be wrong?

The carb is tagged AUC786. The bore is marked AUC6040AC. The jet is .100".

Thanks for your help.

Mike



Mike.Sanford@comcast.net


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