check for the amount of freeplay you have in the choke linkage rod where
the screw passes through it and into the bottom end of the jet.
I've seen perfectly good carb setups that ran like crap (unpredictable idle)
because the hole wears out and you can move your jet body up and
down as much as two 'needle stages'. This also will limit how well
the choke return spring seats the jet tube when you release the choke.
This can amount to as much as 6 'flats' worth of slop in your mixture settings.
Paul Tegler wizardz@toad.net http://www.teglerizer.com (new layout)
OBie - '73 BGT - daily driver
Punkin' - '78 Spitfire - corner ripping screamer
Lil' Greenee - '73 RWA Midget - lady killer
-----Original Message-----
From: Dean Dashwood <Dean.Dashwood@enron.com>
To: td214@cam.ac.uk <td214@cam.ac.uk>; spitfires@autox.team.net
<spitfires@autox.team.net>
Date: Monday, April 17, 2000 11:54 AM
Subject: RE: Throttle control problems
Tim,
I have an identical problem to this. I also have twin SUs (HS4s) and until this
weekend the car would often idle at around 1500rpm, with a little blip on the
throttle settling it back down to 750rpm. This didn't bother me (1500rpm is not
too much to handle) but I put it down to the frayed throttle cable. Eventually
got round to replacing the cable, but this made no difference, so I forgot about
it.
Since getting a little too close to the tyre-wall this weekend, though, the idle
speed has gone up to about 2500rpm, with a blip on the throttle usually putting
it back to normal, but sometimes making it worse, so I was planning on looking
at it in more detail this weekend. My first plan was to check the pistons in
the carbs.
If you fix this, I'd be interested to know what it was. Likewise, I'll let you
know if I manage to fix mine.
Dean
---------------
Date: Mon, 17 Apr 2000 08:30:07 -0400
From: "Bowen, Patrick A RP2" <PABowen@sar.med.navy.mil>
Subject: RE: Throttle control problems
Tim, my answer would be you have a frayed cable, but you say it is new. I
would take a second look at it anyhow.
Patrick Bowen
- -----Original Message-----
From: T. .R. Dafforn [mailto:td214@cam.ac.uk]
Sent: Monday, April 17, 2000 5:44 AM
To: spitfires
Subject: Throttle control problems
Hi Listers,
Finally after 2 1/2 years my car is legal again...
However I have just picked up a problem...
While driving back from the test station the throttle seems to stick
open causing the car to idle at 3K rpm...
Quick blip on the throttle and it dropped back to idle at 750 rpm...
Then it happened again 5K rpm...
blip and back down..
Got back and had a look at the throttle linkages, they seem fine
although the car has never had the return spring which attaches to the
header are these required? It has always relied on the return springs on
the carb...
Also noticed that the rear float bowl was leaking where the tube from
the jet screws in....
Does any one have any ideas whether the problem is mixture or sticking
throttle cable (which btw is brand new!!)
hope some one can help
cheers
Tim
PS the car is a 1500 twin SU carb...
- --
Tim Dafforn
Structural Medicine
Department of Haematology
CIMR
University of Cambridge
Wellcome-MRC Building (Level6)
Hills Road
Cambridge
CB2 2XY
Tel. (01223) 336829
Fax. (01223) 336827
http://smokeroom.cimr.cam.ac.uk/
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