petegardner_901 Posted October 23, 2018 Report Share Posted October 23, 2018 Hi I have checked the forum but anyone any ideas on the following: 1979 Spitfire with twin HS4's. They are the waxstat type and as I was having a lot of problems with idle speed I decided I'd do the usual trick of removing the thermostat in the jet - replaced with 2x 1p coins as recommended by many.... I expected to have to readjust the mix but I cannot get anything but a rich mixture on a Colourtune - the jets are screwed almost right up. Rather stupidly I didn't try checking the mixture before I took out the thermostat but I'm sure it was too rich before anyway. Rather than put the whole lot back just as a check - any ideas??? Thanks Pete Link to comment Share on other sites More sharing options...
yorkshire_spam Posted October 23, 2018 Report Share Posted October 23, 2018 How does the mix look on higher revs? My Spit is the same, twin hs4 with the 2p mod. I can't get it to be anything other than rich at idle if I want it to pull further up the throttle/rev range. I've tried a few different needles and some are better than others, but fundamentally I can have rich idle and good performance or "right" idle and no guts. I think the 2x1p coins are too thin to get the jets back to the right starting position. Link to comment Share on other sites More sharing options...
petegardner_901 Posted October 23, 2018 Author Report Share Posted October 23, 2018 Hi Thanks York - I was thinking that about the thickness of the coins, but then decided that I had screwed the jet up much higher trying to get a weaker mix than the thickness of the thermostat anyway... I don't suppose you have the number of a weaker needle I could try? P Link to comment Share on other sites More sharing options...
yorkshire_spam Posted October 23, 2018 Report Share Posted October 23, 2018 I'll have a look at which needles I'm on and get back to you. It's not so much a weaker needle.... more a richer needle at the top end, so that it can be tuned a little weaker at idle. (Jet higher) Link to comment Share on other sites More sharing options...
petegardner_901 Posted October 23, 2018 Author Report Share Posted October 23, 2018 Many thanks! Link to comment Share on other sites More sharing options...
Nick Jones Posted October 23, 2018 Report Share Posted October 23, 2018 IIRC all SU needles have the same diameter at the idle "station". Constantly rich at idle usually means that there is a problem with the float level setting or that the needle valves are leaking slightly, both causing the fuel level to be too high. The latter can in turn be the result of a repro fuel pump producing excessive pressure. Nick Link to comment Share on other sites More sharing options...
yorkshire_spam Posted October 23, 2018 Report Share Posted October 23, 2018 Hs4 on my 78 spitfire don't have any float adjustment. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 23, 2018 Report Share Posted October 23, 2018 My guess is when fitting the 2x 1p you have left out the short spacer which has to be in place its probably stuck in thebend of the wax capsule Pete 1 Link to comment Share on other sites More sharing options...
yorkshire_spam Posted October 23, 2018 Report Share Posted October 23, 2018 16 minutes ago, Pete Lewis said: My guess is when fitting the 2x 1p you have left out the short spacer which has to be in place its probably stuck in thebend of the wax capsule Pete Oooh good call, I remember that being an annoyance when I did mine first time. Link to comment Share on other sites More sharing options...
Nick Jones Posted October 23, 2018 Report Share Posted October 23, 2018 3 hours ago, yorkshire_spam said: Hs4 on my 78 spitfire don't have any float adjustment. Different thickness sealing washers used. Though not normally required. N Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 24, 2018 Report Share Posted October 24, 2018 hs4 on mine have a fixed float only changes by very thin shim washers under the valve seat, i did find flooding due to a fine ridge of wear in the plastic float could jam the needle valve , no amount of fine fettling solves it a new float was the remedy, needs a good magnifier to see the wear lines . but this is going to be the missed spacer . Pete Link to comment Share on other sites More sharing options...
petegardner_901 Posted October 24, 2018 Author Report Share Posted October 24, 2018 Hey Pete Can't seem to attach a pic to a private message - but - is THIS the spacer you are referring to? It seemed part of the thermostat but should I have a go at removing it...! Link to comment Share on other sites More sharing options...
yorkshire_spam Posted October 24, 2018 Report Share Posted October 24, 2018 That's the one, it pulls out and then sits on top of the coins. Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 24, 2018 Report Share Posted October 24, 2018 yes YS is spot on , give it a tug with some pliers ...or teeth , it gets stuck with fuel residue etc. its just a semi loose fit ...really !! Pete Link to comment Share on other sites More sharing options...
petegardner_901 Posted October 24, 2018 Author Report Share Posted October 24, 2018 You guys are complete aces.... Many thanks. have a photo as a reward...!!!!!! (Yes - I like yellow) 2 Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 24, 2018 Report Share Posted October 24, 2018 No aces just years of problem solving and trying to remember the answers !!! Pete Link to comment Share on other sites More sharing options...
petegardner_901 Posted October 27, 2018 Author Report Share Posted October 27, 2018 Just fixed it all. Car is now running much much better. Good call ! P 1 Link to comment Share on other sites More sharing options...
Pete Lewis Posted October 27, 2018 Report Share Posted October 27, 2018 its good when the fix is easy and ......cheap well done Pete Link to comment Share on other sites More sharing options...
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