jamie hart Posted January 23, 2020 Report Share Posted January 23, 2020 I used HS6 carbs when I rebuilt my 64 TR4 a few years ago instead of the strombergs I suspect I fitted the throttle connecting rod the wrong way round but it worked fine till recently when the engine races at rest indicating the butterflies haven't completetly closed Doe any one have a pic of the linkage set up on a late 4A with SU's so I can check my assembly please? Many thanks Jamie Quote Link to post Share on other sites
MKTR Posted January 23, 2020 Report Share Posted January 23, 2020 some images here - http://joecurto.com/triumph-tr4-su-hs6- Quote Link to post Share on other sites
rcreweread Posted January 23, 2020 Report Share Posted January 23, 2020 (edited) Jamie - look at my refurbished set in Classifieds - quite a few angles to see - if no good, let me know as I have more photos Just added a direct to save you hunting for the ad: https://www.tr-register.co.uk/classified/3076/Pair-of-175-HS6-SUs-on-TR4-or-4A-Manifold-fully-refurbished-with-all-Linkages cheers Rich Edited January 24, 2020 by rcreweread added link Quote Link to post Share on other sites
tim hunt Posted January 24, 2020 Report Share Posted January 24, 2020 These might help too Jamie, as on my 4A (pre- ceramic coating of exhaust manifold). Tim Quote Link to post Share on other sites
Tr4aJim Posted January 24, 2020 Report Share Posted January 24, 2020 Jamie, I had the same problem on my TR4a a few years ago. Initial inspection pointed to a problem with the return spring on the forward HS6. However after closer inspection, I found that a PO had used a bellcrank bracket (75) from a different car (possibly a TR6). This bracket anchors the bottom of the throttle return springs. The incorrect bracket caused the forward return spring to sit at an angle rather than vertical, increasing its travel. I guess over time that forward spring stretched more than the rear one, causing it not to fully close the forward butterfly at rest. I installed the correct bracket, (with new springs), and problem solved. BTW - the attached parts diagram appears to show the link rod (73) connecting to the rear most hole on the bellcrank (71). It actually connects to the forward most hole (the vertical link rod, 70, connects to the rear most hole). See Tim’s picture. Jim Quote Link to post Share on other sites
MRG1965 Posted January 24, 2020 Report Share Posted January 24, 2020 HI, might also be an air leak, my 64 TR has HS6 fitted and the previous owner fit a few extra springs to try to force the butterfly closed, but I've always had an annoying issue that the engine would randomly idle at around 1500 rpm once warm. I only found that I'd accidentally cured the problem when I replaced the crank case breather pipes between the rocker cover and both carbs last summer. Mark Quote Link to post Share on other sites
Drewmotty Posted January 24, 2020 Report Share Posted January 24, 2020 1 hour ago, Tr4aJim said: I had the same problem on my TR4a a few years ago. Initial inspection pointed to a problem with the return spring on the forward HS6. However after closer inspection, I found that a PO had used a bellcrank bracket (75) from a different car (possibly a TR6). The correct bracket wasn't available for some time and conversion kits were sold using a bracket from a USA spec carb equipped TR6. The correct brackets have since become available. Quote Link to post Share on other sites
jamie hart Posted January 29, 2020 Author Report Share Posted January 29, 2020 Many thanks to you all for the information supplied. The problem is in the process of being solved as I noticed several other small issues that I also need to sort out at the same time!! Jamie Quote Link to post Share on other sites
Drewmotty Posted January 29, 2020 Report Share Posted January 29, 2020 2 hours ago, jamie hart said: I noticed several other small issues that I also need to sort out at the same time!! Sounds pretty familiar to me Jamie. Quote Link to post Share on other sites
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