Hi Dean,
Richard Gosling as contacted me off list, suggesting that it may be the result
of
worn throttle shafts, and recomends replacing them and putting bushes into the
carb
body to run them in...
Have you tried this?
I also thuought that the pistons may be sticking,
but
1) Does this result in over-reving?
2) I cleaned mine before I went for the run...
As to living with it, stopping in traffic and waiting to find out just how many
rpm
a spit engine will do before the pistons leap through the bonnet looses its
attraction after a while!!
Thanks for the Help
keep me informed
Tim
Dean Dashwood wrote:
> 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/
--
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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