Bradders Posted May 25, 2020 Share Posted May 25, 2020 Hi I have new needles and jets recently fitted to the twin HS2s on my mkIV and I am trying to set them up following the well trodden path described in the Haynes manual. I can follow it fine but it seems I need to enrich each carb by at least 10 flats above the initial 12 'default' setting to get it running smoothly and to respond correctly when lifting the piston a touch with the lifting pin. However, this setting gives me quite a black sooty exhaust emission indicating it's too rich. I guess all I can do is tweak it to a compromise but could I be missing something here which would lead to this behaviour? Furthermore, although the setting is car-specific, I would be interested to know if 10 flats is typical, does anyone have an idea of the number needed to get it right on their car? Cheers Bradders Quote Link to comment Share on other sites More sharing options...
RobPearce Posted May 25, 2020 Share Posted May 25, 2020 I would say ten flats is unusually many. Most cars run perfectly fine on the initial setting and only need a couple of flats either way for optimum. As you say the exhaust is sooty, I'd say you're probably going far too rich - perhaps your piston lift test isn't quite right? It needs a fairly subtle touch. Or perhaps you have an air leak somewhere that's throwing it all off. Why did you change the jets and needles? Was it running poorly before? Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Thanks for the reply. Changing the jets and needles was one of many things I had to do to get my car going again after a long time sat dormant (best part of 10 years). In that time the carbs had become gummed up with old fuel and a few of the rubber fuel lines had disintegrated. So i have been stripping and cleaning everything I can but a set of new jets and needles seemed a better bet in this area. As of right now, everything is back together and running in the garage. I can get it started and it will rev freely enough but the idle is rough and any load on the engine (going up and down my driveway) causes it to cough and splutter. Timing appears fine at what I think is 6btdc (I only have unlabelled notches on the crankshaft pulley and a single pointer on the timing chain casing to go by). I think a vacuum leak is a likely issue but so far I have failed to find one (spraying wd40 at the suspect areas when the engine is warm and idling hasn't shown anything). Apart from the manifold connections and the throttle spindles is there anywhere else to check? Thanks again. Quote Link to comment Share on other sites More sharing options...
RobPearce Posted May 25, 2020 Share Posted May 25, 2020 OK, possibly silly question, are you managing to get the engine properly warmed up? You can't set the mixture on a cold engine and you can't really get it warm in the right way without driving it further than up and down your drive! Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Well I have it running for some time before I start adjusting anything and it doesnt take long to get the temp needle to the centre of the gauge in this weather. As for my driveway punts it is just a relatively safe place to try it out. The last time I tried to be more adventurous I ended up stranded at the end of my road! That time it was sticking floats (now fixed hopefully). My driveway is a bit of a slope but it really struggles to pull it the 20 or 30 yards up it at the moment. Cheers Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted May 25, 2020 Share Posted May 25, 2020 1. make sure you have tightened the inlet manifold gasket properly.....you could be sucking too much air in 2. which needles have you fitted? As stated the normal 12 flats should get you running as near to normal....if turning another 10 then that is definitely too rich Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Hi I have fitted standard AAN needles. I believe this is what was there before but the old ones did not have markings. Earlier today I decided to strip the carbs to check on the throttle spindles (the manifold nuts were definitely tight). There was some play, not much but enough to notice (see the pic). Not sure if this is the cause or a contributory factor but I will replace them anyway. One other thing I noticed was that the heat shield I have appeared to be 'delaminating', it's not stainless steel but a sheet of layered material. I will ,leave that off when i refit to see if the makes a difference. Cheers Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Hi I have fitted standard AAN needles. I believe this is what was there before but the old ones did not have markings. Earlier today I decided to strip the carbs to check on the throttle spindles (the manifold nuts were definitely tight). There was some play, not much but enough to notice (see the pic). Not sure if this is the cause or a contributory factor but I will replace them anyway. One other thing I noticed was that the heat shield I have appeared to be 'delaminating', it's not stainless steel but a sheet of layered material. I will ,leave that off when i refit to see if the makes a difference. Cheers Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Hi I have fitted standard AAN needles. I believe this is what was there before but the old ones did not have markings. Earlier today I decided to strip the carbs to check on the throttle spindles (the manifold nuts were definitely tight). There was some play, not much but enough to notice (see the pic). Not sure if this is the cause or a contributory factor but I will replace them anyway. One other thing I noticed was that the heat shield I have appeared to be 'delaminating', it's not stainless steel but a sheet of layered material. I will ,leave that off when i refit to see if the makes a difference. Cheers Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 25, 2020 Author Share Posted May 25, 2020 Missing pic... Quote Link to comment Share on other sites More sharing options...
RobPearce Posted May 26, 2020 Share Posted May 26, 2020 That shaft is really quite badly worn. It will have been making it very hard to set the mixture properly. You should definitely replace them! Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 26, 2020 Author Share Posted May 26, 2020 Hi New shafts on order and hopefully they will be here within the week. I will give them a go and post an update afterwards. Thanks for the responses and help. Cheers Quote Link to comment Share on other sites More sharing options...
Velocita Rosso Posted May 26, 2020 Share Posted May 26, 2020 You may find most have AAQ needles Quote Link to comment Share on other sites More sharing options...
Tel Posted May 26, 2020 Share Posted May 26, 2020 Quoted from Bradders- Well I have it running for some time before I start adjusting anything and it doesnt take long to get the temp needle to the centre of the gauge in this weather. As for my driveway punts it is just a relatively safe place to try it out. The last time I tried to be more adventurous I ended up stranded at the end of my road! That time it was sticking floats (now fixed hopefully). My driveway is a bit of a slope but it really struggles to pull it the 20 or 30 yards up it at the moment. Cheers Quoted from Bradders- Hi I have new needles and jets recently fitted to the twin HS2s on my mkIV and I am trying to set them up following the well trodden path described in the Haynes manual. I can follow it fine but it seems I need to enrich each carb by at least 10 flats above the initial 12 'default' setting to get it running smoothly and to respond correctly when lifting the piston a touch with the lifting pin. However, this setting gives me quite a black sooty exhaust emission indicating it's too rich. I guess all I can do is tweak it to a compromise but could I be missing something here which would lead to this behaviour? Furthermore, although the setting is car-specific, I would be interested to know if 10 flats is typical, does anyone have an idea of the number needed to get it right on their car? Cheers Bradders Quoted from Bradders- Hi I have new needles and jets recently fitted to the twin HS2s on my mkIV and I am trying to set them up following the well trodden path described in the Haynes manual. I can follow it fine but it seems I need to enrich each carb by at least 10 flats above the initial 12 'default' setting to get it running smoothly and to respond correctly when lifting the piston a touch with the lifting pin. However, this setting gives me quite a black sooty exhaust emission indicating it's too rich. I guess all I can do is tweak it to a compromise but could I be missing something here which would lead to this behaviour? Furthermore, although the setting is car-specific, I would be interested to know if 10 flats is typical, does anyone have an idea of the number needed to get it right on their car? Cheers Bradders Worked for SU once always set jet at 2 turns for start up, Make sure needle is set flush with the bottom of piston Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 27, 2020 Author Share Posted May 27, 2020 Hi Whilst waiting for the new shafts to turn up I came across a version of the shaft modified with rubber o rings to help form a seal on Ebay (search for 'SU CARB HS2 new throttle shaft.'). A bit late for me but it looks like a good idea. Anyone got any opinions or, better still, experience of them. Pic below Cheers Quote Link to comment Share on other sites More sharing options...
Bradders Posted May 27, 2020 Author Share Posted May 27, 2020 Missing pic Quote Link to comment Share on other sites More sharing options...
nang Posted May 28, 2020 Share Posted May 28, 2020 You'll need to be sure that the bore in carb body is not worn oval or you will need to get that bushed also. Tony Quote Link to comment Share on other sites More sharing options...
Bradders Posted June 8, 2020 Author Share Posted June 8, 2020 Hi Just an update but a happy one. I fitted the new spindles and was fortunate that the bores were not worn on the carb body so the fit was snug. This was an improvement but not enough to get it right. However, after tweaking the float heights and replacing a kinked/pinched fuel line I now have it running better than I can remember. On the subject of the initial jet settings and the number of flats to turn I now understand where I went wrong. I was following the usual advice of tightening the jet up all the way and backing off 12 flats but this did not take into account the amount needed to first get the jet level with the bridge (something that most guides seem to omit or at least the ones I have read). It took 6 or 7 flats to reach this point before applying the 12 so around 19 in total. Now it all makes sense! With the other changes I barely need to go beyond the 12 to have it smooth and even. Now I just need to get some welding done....... Cheers Quote Link to comment Share on other sites More sharing options...
A TR7 16V Posted July 16, 2020 Share Posted July 16, 2020 Quoted from Bradders- Hi I have new needles and jets recently fitted to the twin HS2s on my mkIV and I am trying to set them up following the well trodden path described in the Haynes manual. I can follow it fine but it seems I need to enrich each carb by at least 10 flats above the initial 12 'default' setting to get it running smoothly and to respond correctly when lifting the piston a touch with the lifting pin. However, this setting gives me quite a black sooty exhaust emission indicating it's too rich. I guess all I can do is tweak it to a compromise but could I be missing something here which would lead to this behaviour? Furthermore, although the setting is car-specific, I would be interested to know if 10 flats is typical, does anyone have an idea of the number needed to get it right on their car? Cheers Bradders I just had exactly this problem on my Dolomite Sprint. It turned out that it was the filters that were clogged. I have K&Ns fitted, and I don't take them off to set the jets flat to the step - I've taken to using a vernier recently as well. So I take the dashpots off and check they're flat that way. Anyway, the jets were about 10 flats up near the step to get the idle maxed, etc., and that gave a sooty exhaust and black plugs. But turning the jets down where they should be, and getting the plugs a good colour made it gasp badly and dig in setting out from a stop, and it didn't run well at all. Anyway, long story shorter, I got the K&N cleaner stuff and did the filters properly and the job's a goodun. Graham Quote Link to comment Share on other sites More sharing options...
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