Rich_s Posted March 16, 2014 Author Share Posted March 16, 2014 oops missed last one: Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 16, 2014 Share Posted March 16, 2014 I checked my later pistons and they have a piece of black plastic so that sounds right. But I am thinking you may have a bitsa carb setup as only 1 carb has this, plus the jet bearing is probably from earlier carbs.I'll take some photos of my late carbs and post them later.Do you know what needles you have? Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 16, 2014 Author Share Posted March 16, 2014 both pistons have the plastic sticking out but one is about .25mm where as the other is more like 1mm if not more. thanks, appreciated.the rest of the carbs all seem to tally up as expected, both needles are the same and are ADN needles. so guessing the wrong jet bearing is having an adverse effect and causing the jet to need to be far lower than normal. Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 16, 2014 Share Posted March 16, 2014 The jet bearing should not affect the position of the jet, this is set to the needle, if the needle is too low then the jet will be too low. Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 16, 2014 Author Share Posted March 16, 2014 the needles look to be the same and cant see how the height could be altered as they look to go in from the top, could be wrong though.just wondered if because of the bearing being too low it was affecting the air flow over the top of the jet so less fuel is being sucked in, not an expect in air flow though, thinking for the sake of £20 i may just get new ones and see how it goes.rich Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 16, 2014 Share Posted March 16, 2014 Hi Rich, the needle moves. As more air is sucked in the damper rises making the needle rise to thinner point allowing more fuel through. So if the needle is lower then the optimum idle point is lower therefore the jet will be lower. But it can only really go down so far. I have made progress today, rebuilt carbs fitted and looks like I have got the mixture right and the carbs balanced, just stopped for a cuppa then back out to set the choke. Had a big leak though, the pipe from the jets to the float chamber needed tightening more than I had. I think the old carbs were leaking as I was finding it difficult to set them properly, but then they have done over 200,000 miles ;D Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 16, 2014 Share Posted March 16, 2014 Hi Rich, I was nearly finished when I loosened one of the pipes to the float chamber accidently, another leak so I am leaving it to another day to finish.Anyway I have a few photos that may help you.Pic one is the later carb (FXZ1122 ) damper with the needle correctly installed, pic 2 shows it incorrectly installed. The needle comes out from underneath, its secured by the screw you can see.I suspect that if the needle is proud it will bottom out, but this could prevent the piston from returning properly causing fast idle and a mixture setting imbalance between the 2 carbs.In pic 1 you can also see the piece of black plastic and 2 holes in the bottom of the piston.Pic 3 is the jet adjuster position now I have the carb set up.I do think you have the incorrect bearings for your carbs so no problem if you want to get the correct ones. On the FZX1258 carbs I have the bearing is the same as yours. Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 16, 2014 Author Share Posted March 16, 2014 The needles on mine look the same as your first pic, wasnt sure how they came out as i took the screw out but that didnt loosen anything off ;D but i could read the type through the hole. at the moment i am just wondering how mine is at 5.5 turns out with everything else std apart from the jet bearing, seems they are more than double where they should be but mixture is right, maybe slightly lean if anything.any idea what that bit of plastic is, guessing mine shouldnt stick out that much, should it stick out at all do you know?rich Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 16, 2014 Share Posted March 16, 2014 On mine the black plastic bit is a bung, it sticks out about 0.5mm.When I set up the carbs this afternoon I started with the jet flush with the bridge in the carburettor. Turned it down by 12 flats, but I forgot to fit the pipes from the rocker cover and ended up turning the jets down much further to get it to run, maybe worth checking your breather system if you have not done so yet. Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 18, 2014 Author Share Posted March 18, 2014 I have checked the breather pipes and they are all ok and sealed nicely, but wondering if it could be sucking in too much air from the rocker box somehow, filler cap seems tight enough and base seal seems ok but could it get in anywhere else?might try linking the 2 carbs so i know its not sucking in anymore air from anywhere and see if that makes any difference...rich Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 19, 2014 Share Posted March 19, 2014 I had a thought, the jet on my conversion kit are longer than the waxstat jets. If you start with the jets fully wound up then you will have to wind them down further than the waxstat jets to get the same position for the top of the jets. Could this be your problem? Quote Link to comment Share on other sites More sharing options...
nang Posted March 20, 2014 Share Posted March 20, 2014 Needle base must be flush with the carb body, your last pic, the adjustment seems to be screwed down too much. May help? If you have a pair of digital calipers or one with a dial gauge, set the jet down from the body .050" as an initial adjustment. Much easier than counting the flats.Tony. Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 20, 2014 Author Share Posted March 20, 2014 Hi Tony,I have tried that, the car wont run with the jet that high at the moment with the jets as per the pics its running slightly on the lean side. i am going fit a diff breather pipe so both carbs are linked but not connected to the rocker box and see how it goes, can then just rig up a simple breather bottle to catch the fumes in.Rich Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 23, 2014 Author Share Posted March 23, 2014 bit of a day sorting problems on my car, checked the mixture using a colortune and its the same linking the 2 carb breather pipes to each other or if i leave it std and sucks from the rocker box, only thing left now is the jet bearings themselves i think so thats next on the list....rich Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted March 23, 2014 Share Posted March 23, 2014 Hi Rich, some info for reference, I dismantled the jet on a spare hs4 carb I have:(dimensions to nearest 0.1mm and all in mm)And a quick pic: Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 23, 2014 Author Share Posted March 23, 2014 thanks for thatm the figures for mine are far less, mine is 4.0 instead of 6.2 and 19.5 instead of 26.1 so looks like quite a bit out....time to get spending a few more pennies on this car i think in quest to get it all running as it should be.thanks again, most appreciated.rich Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted March 23, 2014 Share Posted March 23, 2014 Hi Rich,When I saw this: http://www.leacyclassics.com/wzx1443.htmlI was a bit worried yours was right and mine wrong, so I dashed out to the garage and pulled the jet bearing out of the bottom of a carb that's on my running 1500 (rather than a spare out of a box on the shelf!) - the one off the car measures 6.2mm on the top as well. Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 23, 2014 Author Share Posted March 23, 2014 As far as i know yours looks like most i have seen with mine being an odd version, am guessing there must be a version of the HS4 which needs the smaller version, its not the ones i have though ;D wonder if i have the wrong tags as well? or their website is wrong.will have to double check sizes before ordering i think and not go off the part codes....thanksrich Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted March 23, 2014 Share Posted March 23, 2014 For what it's worth, tags on mine are (F)ZX1258 F/R. Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 23, 2014 Share Posted March 23, 2014 As I said earlier the older HS4 carbs have a different jet bearing, this is the set I am now using. The major difference to the later carbs is the dashpots. Yesterday I swapped back to the non waxstat conversion jets due to a leak. My problem with the conversion kit was a gunked up linkage causing one of the jets to stick open on choke. I set them to 12 flats as normal, tuning resulted in making them a bit leaner, less than 2mm below the bridge and slightly higher than the jet bearing. If yours are much lower then they must be too rich, I cannot see this being the result of the jet bearing. What happens to the engine speed if you raise the piston 1/4"? Quote Link to comment Share on other sites More sharing options...
Rich_s Posted March 23, 2014 Author Share Posted March 23, 2014 thats how i thought they would be, but nope. currently at 33 flats out from fully in but not sure if this is higher than bridge or not, tested with colour tune today and blue spark/flame when ticking over and if open the throttle it goes orange briefly then back to blue again, cant try lifting pins as both are seized up.all i can think is the jet bearing being low is allowing air to be drawn through the gap instead of over the jet sucking in fuel..... only a guess though as have ruled out it getting extra air anywhere else, everything else is clean and std Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted March 23, 2014 Share Posted March 23, 2014 If the threaded part is roughly the same length, but the plain shank is shorter, then with the jet screwed fully up it'll be a lot higher. So you have to turn it down a lot further to get to the same place.If you see what I mean? Quote Link to comment Share on other sites More sharing options...
Pete Lee Posted March 23, 2014 Share Posted March 23, 2014 932 wrote:thats how i thought they would be, but nope. currently at 33 flats out from fully in but not sure if this is higher than bridge or not, tested with colour tune today and blue spark/flame when ticking over and if open the throttle it goes orange briefly then back to blue again, cant try lifting pins as both are seized up.I think this is part of the problem, 12 flats is from when the top of the jet is level with the bridge not from the fully wound in position. If from the fully wound up position then you could be winding out by 30odd flats. You can use a drill of the correct size to lift the piston, it should be 1/16" diabetes not 1/4" as I said before. Personally I don't like the colour tune I find listening to the engine far easier and accurate when adjusting the mixture.There are some very useful articles on the mgb experience website on SU carburettors, including an excellent one by Roger Garnett. Quote Link to comment Share on other sites More sharing options...
yorkshire_spam Posted April 1, 2014 Share Posted April 1, 2014 Hey Rich! Guess what I found when I took a FZX1122 carb apart this evening......Look familiar? ;) Quote Link to comment Share on other sites More sharing options...
.thumb.jpeg.b15b81ef10abeea1c3039ae03c4a9f3a.jpeg)
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.