Hi James
James Carruthers wrote:
> I spent saturday morning trying to fix the damn jets on the newly installed
>carbs. I successfully got them to stay in place - it ends up the rubber o-ring
>was perished\
Thought so..
> - so I swapped them for the ones in the old carb. I also shortended the fuel
>line that goes around the K&Ns - as that was the thing that caused all the
>trouble in the first place. The wheel arch pushed down on the fuel line - thus
>rotating the jets and putting enough pressure on the small fuel lines (Im yet
>to work out what they are called) to pull them out.
Excellent
> Any way I was quite pleased with my mornings work - this is the first thing
>Ive ever done on an engine! The Rimmer catalogue is almost as useful as the
>Haynes - if not more so in some cases) So I go in for a well earned lunch.
>
> So I return after lunch and plan to drive the car to Halfords to get a
>jubilee clip for one of the water hoses that I had broken in the morning,
>there was only a bit of water coming out - and only over about 4500rpm - so
>driving 3/4 mile would have been a good test for my newly fixed carb unit.
>
> Anyway before I even start down the road to Halfords - the car wont start
>without quite a bit of gas (Im getting more american all the time after
>reading this list so much!) So the car wont start properly. And when it does
>start - the engine dies unless you put sufficient pressure on the gas pedal.
>So I check the throttle cable. Thats ok - everything is ok. I had driven about
>40 miles with these carbs a couple of days before. Worse still was the fact
>that pulling out the choke made the engine die altogether.
>
Did you adjust the throttle stop screws? these control the engine speed at
idle, and may need turning up..
When you fit K&Ns to the spitfire it increases the ease with which air is
pulled into the carbs. This means that the needle in the carb that meters the
amount of fuel being sucked into the airflow may now be wrong. With just K&Ns
this should just mean that every thing is a little lean, and you may not notice
too much.
By the sounds of things, the actual mixture you are running is too rich, and
that can probably just be sorted out by leaning out the jet adjusting screws a
little. Also make sure that when you pull your choke the jets slide up and down
nicely...
Mine had a tendency to jam leaving one or other carb running mega rich...
>
> To cut a long story short, after fiddling about - and having enough fuel over
>my hands for the day (and having cut the back of my hands to threads on the
>end of the choke cable - ouch!) I decided enough was enough, so I fitted the
>old carbs back on. That took 30 mins or so - not bad for a first time I think
>you'll agree. So Im back with my car as it was. Without the new carbs and
>without the K&N's.
>
Not bad at all..
Why not put the K&Ns straight on the carbs you know work?
>
> I do plan to try the K&N carbs again - when I have time and have figured out
>whats wrong with them. Or if it was just me being impatient. They did make a
>lot of difference when they were working - the engine was much smoother - in
>power and in sound.
>
> Another strange thing that happeded to me as well: After fitting the new
>carbs - the power from the engine "throbbed" all the way home (that was the
>40mile motorway journey) This didnt strike me as strange originally - as I
>knew the carbs needed tuning a bit more. And considering the fact that one of
>the jet lines wasnt connected properly. What I dont understand is the fact
>that when I fitted the old carbs back on again - it started throbbing again -
>I gave the car a good thrash a few hours after after fitting the them. However
>the next day it was back to its normal self again. And this morning its fine
>too. What is this throbbing then?
>
Sounds a little like bad synchronising, or perhaps a bit of dirt in the fuel
lines blocking the fuel flow..
Cheers
Tim
>
> James
>
> 77 Pimento Red Spit - now with the old carbs and boring old BL air box &
>filters.
>
--
Tim Dafforn
University of Cambridge
Structural Medicine Unit
Cambridge Institute for Medical Research
Hills Rd, Cambridge CB2 2XY.
UK
Tel. (01223) 763230
Fax. (01223) 336827
http://smokeroom.cimr.cam.ac.uk/
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