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Posted By : Stuart Evans, 28-Jul-2007, 10:12pm
Hi All
My stag is fitted with a 2500cc engine from a 2500tc, i was giving her a service and a bit of a tune up today
But i had trouble adjusting the mixture (currently running to rich), i started by screwing the mixture adjusting nuts all the way in which took 33 flats on
each carb.
When i had my spitfire and set the carbs i was told the you screw the nuts all the way in and then screw them out by 12 flats and that would not be far
off.
So i screwed the nuts out by 12 flats and it would'nt start, so i carried on till 33 flats and she started first time.
Is there something amiss or does this sound about right for HS6 carbs?
Any advice would be welcome
Cheers
Stuart
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Posted By : Chris Taylor, 29-Jul-2007,
06:56am
It's worth investigating whether you have the correct metering needles.
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Posted By : Clive Senior,
29-Jul-2007, 07:51am
Shouldn't make any difference to get idle.
It may be low fuel levels in the float chambers? Needles seated in their pistons correctly?
And you say to start, so I assume the engine is nice and warm, otherwise you will/may need choke to start it! Once running and warm you can then
make the adjustments.
As a guide to needles if you are running HS6 on a 2500 with decent air filters, something like BDQ needles work well. The BDB(??? from memory, do
check) are far too lean once the car is running on the road. My vitesse 2.5 wouldn't run over 3000rpm at all with K+N's on the "proper" needles.
They only work if you have the 2500airbox fitted, which is VERY restrictive. But all this is irrelevent at idle! So which filters are fitted?
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Posted By : Stuart Evans, 29-Jul-2007,
02:09pm
I have K&N filters fitted and no other mods
The running of the car when on the road is fine, can be a bit jumpy when driving at low speeds in a high gear but other than that she pulls
great though the rev range.
Tick over is quite lumpy but the colour tune indicates the the mixture is fine on tick over
The needles fitted are BFZ which looking at the sizes of the stations they are only slightly weaker than BDQ needles (thats if the size of
station i.e. 710 is weaker than 690)
It's just confused me a bit with having to wind the mixture nuts out so much, never had to adjust that much before
Cheers
Stuart
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Posted By : Chris Taylor,
29-Jul-2007, 06:53pm
Not sure what jets the HS6 should have, but is it possible you have 0.090" jets when you should have 0.1" ones? A smaller jet would need to
be "lower down" a needle designed for the bigger jet to get the same diametric clearance and so flow the same amount of fuel.
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Posted By : Stuart Evans,
31-Jul-2007, 04:49pm
Have checked all the items mentioned so far and these are my findings:
Needles and jets are correct, needles being BFZ and jets being the right size 0.100, they are in good condition with no damage or
blockages.
Float chambers are clean and free of dirt, the floats are the plastic nonadjustable type which are in good condition not holed and
within tolerance and the vavles are woking correctly.
All other components of the carbs look in very good condition with no excess play or movement, no parts look to be missing, with all
gaskets and joints looking good and air tight, and the inlet manifold seems in good condition.
I've been told the there are course and fine theads to the adjusting nuts and the fine type might require more turns than the course,
is there a measurement from the bridge of the carb to jet because there seems to be very little movement in jet height in relation to
the number of flats/turns made to the adjusting nuts.
If anyone else has any ideas please let me know.
Cheers
Stuart