F1loco Posted February 19, 2017 Report Share Posted February 19, 2017 So, been working on the fuel side of things now that I am convinced my ignition system is top notch. Started from scratch and think my weak needle in the rear carb is bent. Without the cover on, it will seat just fine - but put it on it will stick initially upon lifting the piston and not rest all the way down. If I push it back down, the choke on the bottom will push down maybe 1/16" of inch. I tried to reset the needle several times, but still the final bit of needle into the jet seems to be catching. So, I go online to look for needles. But noticed my carbs are tagged - Front/AUD13, Rear/AUD209R. It is a '64 TR4, but discovered upon earlier engine issues, it is a TR4A block. So, first question is do I even have the correct matched SU Carbs in the car? From what I found the AUD13 is for a Morris Minor? If not, what should I be looking for. At this point, I may try to pick up a couple of freshly rebuilt matched sets. Any other suggestions would be greatly appreciated. Quote Link to post Share on other sites
Fireman049 Posted February 19, 2017 Report Share Posted February 19, 2017 When you tried to recentralise the needle did you make sure that you'd screwed up the jet fully first? Tom. Quote Link to post Share on other sites
Lebro Posted February 19, 2017 Report Share Posted February 19, 2017 +1 Quote Link to post Share on other sites
peejay4A Posted February 19, 2017 Report Share Posted February 19, 2017 Something is wrong with one of those tags. 209 is an HS6 and correct but 13 is an HS2, different bore and afaik a different manifold mount. Wrongly labelled I guess. Quote Link to post Share on other sites
monty Posted February 19, 2017 Report Share Posted February 19, 2017 Andrew Turner for advice & spares! Quote Link to post Share on other sites
F1loco Posted February 19, 2017 Author Report Share Posted February 19, 2017 (edited) When you tried to recentralise the needle did you make sure that you'd screwed up the jet fully first? Tom. Correct. Screwed all the way up first. It "drops" freely, but not all the way - it seems to catch on the last 1/16" or so with choke pushed all the way up. If I let the choke get kicked down 1/16", it will drop all the way but will run rich. Edited February 19, 2017 by F1loco Quote Link to post Share on other sites
F1loco Posted February 19, 2017 Author Report Share Posted February 19, 2017 Pics: http://s1067.photobucket.com/user/f1loco/media/IMG_2195_zpspheozbu5.jpg.html http://s1067.photobucket.com/user/f1loco/media/IMG_2195_zpspheozbu5.jpg.html http://s1067.photobucket.com/user/f1loco/media/IMG_2195_zpspheozbu5.jpg.html Quote Link to post Share on other sites
Drewmotty Posted February 19, 2017 Report Share Posted February 19, 2017 (edited) Is the needle seated correctly in the slide? The underside of the locating spigot should be flush with the underside of the slide. It could be that someone has replaced the float bowl cover and the aluminium ident label has Come from the donor carb. Edited February 19, 2017 by Drewmotty Quote Link to post Share on other sites
F1loco Posted February 19, 2017 Author Report Share Posted February 19, 2017 Should the needle be seated as far in as it will go? Noticed that the ridge may have been protruding just a tad. Not sure if I push it in all the way and secure the screw if I will be able to control a rich issue? Quote Link to post Share on other sites
Drewmotty Posted February 19, 2017 Report Share Posted February 19, 2017 (edited) Pushing the needle right home will result in an over rich mixture throughout the range. It should be possible to push it in too far so if it won't go pat the flush position check the slide recess for debris or burrs. Check that you have the correct needle. SM or TW are very similar and work for most standard and mildly tuned engines. The needle spigot must be flush with th slide. Check the needle for straightness by popping the digit in a drill check and looking for runout at the sharp end. Edited February 19, 2017 by Drewmotty Quote Link to post Share on other sites
Lebro Posted February 19, 2017 Report Share Posted February 19, 2017 Sorry if this seems obvious but have you slackened off the large hexagon under the carb (above the mixture adjustment) then wobble the jet around till the needle drops right down ? OK assuming you knew that, next thing to check is the seating of the outer cover on the carb body, make sure there are no high spots, or bits of dirt which may not allow the cover to be completely level. Bob. Quote Link to post Share on other sites
F1loco Posted February 19, 2017 Author Report Share Posted February 19, 2017 Well after reinstalling the needle to what I believe is correct level, it is a bit better, but still the piston does not drop like to should on the rear carb. The front is definitely more free falling than the rear one. Guessing the needle may be ever so slightly bent at towards the base. Mixtures, though, seem spot on. Slight raise, then drop on lifting the pistons. I'll try to find some new needles only - presumably for HS6 carb - and hope for the best. At least I had time to re-dial the choke linkages in as the previous owner clearly did not and the front choke would never engage apparently. Only remaining tackle is to drain/remove the radiator to swap an old fitted Spitfire fan with a TR6 8 blade one and hopefully cut down on over-heating issues here in Florida. Too bad there doesn't appear to be enough room to simply undo and reinstall with radiator in place... Quote Link to post Share on other sites
Drewmotty Posted February 19, 2017 Report Share Posted February 19, 2017 A slight misalignment of the damper/slide housing can cause a problem. Try loosening the three screws and lifting and dropping the slide by hand as you re-tighten them and as Bob has suggested make sure that everything is scrupulously clean. Quote Link to post Share on other sites
Drewmotty Posted February 19, 2017 Report Share Posted February 19, 2017 Try the action of the slide with the needle removed and swapping the slides and housings between carbs to ascertain wether the problem is with the slide, needle or body. The carbs may have assembled in the past with the wrong slide or top to match the body. Quote Link to post Share on other sites
LGFromage Posted February 19, 2017 Report Share Posted February 19, 2017 Your carburetors both look like HS6 types which normally have a the AUD209R designation and 0.100 in dia jet size. Carburetors designated AUD13 normally have a jet size of 0.090 in dia which might explain why the needle does not drop all the way. Tim Quote Link to post Share on other sites
rcreweread Posted February 19, 2017 Report Share Posted February 19, 2017 Why don't you swop the needles between the two carbs and see if the problem follows the potentially bent needle? Cheers Rich Quote Link to post Share on other sites
Fireman049 Posted February 19, 2017 Report Share Posted February 19, 2017 As Bob says ~ have you slackened the 3/8th Whitworth large hexagon nut under the carb. and wobbled the jet around until the piston drops right down ~ I bet you haven't? Tom. Quote Link to post Share on other sites
mike ellis Posted February 19, 2017 Report Share Posted February 19, 2017 normally have a jet size of 0.090 in dia which might explain why the needle does not drop all the way. +1 I have come across this before where someone had fitted 90thou jets to a TR3A and when the present owner put in some new SM needles they would not drop right down. Replacement with correct 100thou jets solved the problem. Quote Link to post Share on other sites
Fireman049 Posted February 19, 2017 Report Share Posted February 19, 2017 Mike has a very valid point! Tom. Quote Link to post Share on other sites
Tonyloz Posted February 20, 2017 Report Share Posted February 20, 2017 How do you know if its a 90 or100 thou jet Quote Link to post Share on other sites
Lebro Posted February 20, 2017 Report Share Posted February 20, 2017 Measure using a selection of small drills Bob. Quote Link to post Share on other sites
F1loco Posted February 20, 2017 Author Report Share Posted February 20, 2017 As Bob says ~ have you slackened the 3/8th Whitworth large hexagon nut under the carb. and wobbled the jet around until the piston drops right down ~ I bet you haven't? Tom. Yes, I have. Quote Link to post Share on other sites
F1loco Posted February 20, 2017 Author Report Share Posted February 20, 2017 Try the action of the slide with the needle removed and swapping the slides and housings between carbs to ascertain wether the problem is with the slide, needle or body. The carbs may have assembled in the past with the wrong slide or top to match the body. Thanks, will give that a whirl today to see if there is any difference as well as removing the needles entirely to be sure the problem isn't up top as well. Quote Link to post Share on other sites
F1loco Posted February 20, 2017 Author Report Share Posted February 20, 2017 Are there any more markings on the carbs that would solve the "is it an AUD13 carb or not?" If I am going to do this, I might as well be sure I'm doing it correctly the first time. Quote Link to post Share on other sites
F1loco Posted February 20, 2017 Author Report Share Posted February 20, 2017 Well my guess is I may have mismatched carbs/needles. I swapped them out and they seem to be working fine now - though the front piston seems to hesitate a tad longer before dropping down. Next question is, do I need (or should I) to replace the AUD13 with a proper HS6 - assuming it has a smaller throat and needle than the rear? Also, I was trying to readjust the linkages. Got the carbs in sync and good air/fuel mix on lifting the pistons and locked them in. However, I noticed when I choke it, it has to be fully pulled out in order for the front choke to engage? At 1/2 choke the front is pushed all the way up. I tried loosening and rotating the front adjustment as much as I could by spinning it further around and locking it in, but the front choke still seems a bit behind the rear. Is this normal or do I need some sort of other adjustment? Quote Link to post Share on other sites
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