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November 4, 2017, 12:14pm Report to Moderator

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Can anyone help me on my su carb dilemmas. I recently became owner of a 1500 spitfire that had been restord magnifciently  by someone earlier and I have final issues to resolve. I can't get the car to meet the emmision test and and whilst in all other respects  the engine runs sweetly I struggle to tune both carbs like the advice given. start from 12 flats etc(open to 24 currently- tickle test to see increase in revs, then die down not achieved) hopefully you can see my picture which shows the jet surround not flush with the bridge. Is this correct or has the wrong item been fitted? Also it has red coloured main jet which has proved difficult to move back fully home (up) when the choke cable is pushed in and has needed an additional return spring. If I disconnect from petrol bowl it moves up and down freely. your views would be appreciated.

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November 7, 2017, 12:56pm Report to Moderator

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Hello Yesfan,

I wonder if someone fitted an 'O' ring to the jet bearing tube, as it is sitting lower than it should? It may possibly have a n influence on the jet not going up as it is meant to? I would remove the jet then the jet bearing and see what is fitted?


Oswestry, Shropshire.

Mk1 1\2 P.I.,Jaguar Mk 2, very long term restoration. Jaguar X Type estate 2.5, Hymer 564 motorhome.
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Don Cook
November 8, 2017, 10:31am Report to Moderator

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What year is your car. Found this on GOV.UK

"Emissions testing
You can’t get an MOT certificate if your vehicle’s exhaust emissions are too high. Emissions may also be tested as part of a roadside check.

Most vehicles have their exhaust emissions tested as part of the MOT.

Usually, they’re tested using a meter. Petrol vehicles used before August 1975 and diesel vehicles used before August 1979 are tested by sight.

If your vehicle fails the emission test it fails the MOT. The problem must be fixed before you can get an MOT certificate.

The only vehicles that don’t have an emissions test as part of the MOT are:

vehicles with less than 4 wheels
those with 2-stroke engines
hybrid vehicles

And this on another site

Vehicles first used prior to 1 August 1975 are exempt from a metered emission test
Vehicles first used on or after 1 August 1975 and before 1 August 1986:
carbon monoxide (CO) 4.5 per cent at idle
hydrocarbons (HC) 1,200ppm (parts per million)"

Not saying you should do this but you could try leaning it off somewhat (Ahem...not in the long run).

Don Cook
Manningtree, Essex

GT6 Mk3 Signal Red (Tomboy). Triumphs in the past: Vitesse 1600, Toledo. Tiger Cub, Thunderbird.

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Several Dutch Rallies.
Some La Carrera Caledonia.

Best trip ever: Ijsselmeer causeway then up through Germany, Denmark...over the two massive bridges of Slorebaeltbroen and Oresund to Ystad in Sweden where we got an overnight ferry to Poland, then on to Berlin etc.
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November 8, 2017, 11:44am Report to Moderator

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I had a similar problem a few years ago on my 1976 Spitfire 1500, my Classic friendly MOT tester couldn’t get the mixture lean enough to pass the emissions test, so he put the probe in the exhaust of another Spitfire that had just passed, no problem!

In his defence he did suggest I changed the wax stat jets for standard ones which I did and resolved the issue at future MOT’s.

(formerly known as 76Spit)
Location : Garden of England near Maidstone (or the bit the Lorries pass through on their way to rest of the UK!)

1978 Stag Russet Brown BW65 3.0 V8 - Faversham's built -  CAR 12 2011 10CR FINISHER-2012 & 2014 RBRR FINISHER
2012 Ford SMax 1.6TDCI Zetec
2014 Skoda Citigo SE 5 dr
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November 10, 2017, 12:55pm Report to Moderator

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Thanks for your comments so far. As regards MOT , lets say I have a friendy tester and I am on the road. I believe the car will be exempt from testing on its 40th anniversary anyway. I have had the jet and bearing out and everything seems fine. somewhere  i read there was a bearing that was 2mm shorter or longer but this difference looks to be about 5mm. There is no scope for adjustments.
I have no history on its past. It would appear that someone had spent many years lavishly restoring it and had to get rid of it rather quickly as it was hastily put back together and disposed of, maybe save their marriage ( it spitty or me!) Its reg starts with the letters MUD and is on the s plate. I am going to look at an Healey midget twin su's to see if I can further enlighten myself.
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November 11, 2017, 7:54am Report to Moderator

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Hello Yesfan,

my (admittedly rather old) Burlen S.U. manual lists four variations of jet bearing, two fixed needle ones and two biased needle ones, but it says the fixed and biased needle ones are interchangeable, the other variation is coarse (standard) or fine thread adjustment.
However, I suggest you speak to Burlen as they will be able to sort you out very quickly.


Oswestry, Shropshire.

Mk1 1\2 P.I.,Jaguar Mk 2, very long term restoration. Jaguar X Type estate 2.5, Hymer 564 motorhome.
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