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TR4: Setting mixture on SU HS6 Carbs

To: "Triumphs" <triumphs@Autox.Team.Net>
Subject: TR4: Setting mixture on SU HS6 Carbs
From: "Brian Sanborn" <sanborn@net1plus.com>
Date: Fri, 14 Aug 1998 18:26:24 -0400charset="iso-8859-1"
I just spent some hot bent-over-the engine time with my new TR4 trying to
set everything straight on the oil/filter, ignition, carbs, timing and valve
adjustment and so on.

My 35 year old unisyn came out of the old "Auto Parts" box in the basement
to balance the carbs fine. But.... I can't make heads or tails of the
mixture setting.  I am using a Colortune but that seems very inconclusive so
I am using the "lift the piston and if it speeds up turn the mixture in one
flat" method.  My Bricklands TR4/TR4A Workshop Manual has tuning
instructions for the H6 and Strombergs but not the HS6 type.

Can someone tell which way to turn to make it richer and which way to make
it leaner on the late model TR4A type HS6 carbs.  The VTR instructions seem
to imply that the left/right may be reversed.   Mine seem to behave like
turning right makes it leaner.

The engine is running better but now has a "cough" in the idle exhaust and
when it is backing off with the foot off the gas there is almost a tiny
backfire sort of noise.   I know it's not right... but before I spend any
more time on it I wanted to talk to you guys.

I also can't seem  to get the engine to return to the same idle unless I
BLIP the throttle linkage.  It doesn't come back to zero.  I remember this
"feature" from my original 62 TR4 35 years ago.  Is a matter of cleanup and
lubrication?? Should I replace the  return springs??

I feel like I am in a dark room with big baseball gloves on.


Brian Sanborn
62 TR4          CT16260L  - Groton,  MA
sanborn@net1plus.com


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