John Mellor Posted February 12 Report Share Posted February 12 Hi all, started looking into why he runs rich and found that there is surprising resistance to up/down movement of the jet bearing when moving the jet lever by hand when jet control connecting rod is disconnected. Is this normal? I realise that there are washers and seals which introduce friction resisting the movement but how much and might this be an explanation for running rich? The jet needle looks fine with no ridges and it seemed properly central. Guess for many of you this is food and drink but never got into the carb inners on my TR2 ( UTU888 ) all those decades ago and despite my senility I'm a carb virgin!! Regards to all John Mellor Quote Link to post Share on other sites
Steve Priest Posted February 13 Report Share Posted February 13 I can't comment on the TR4A's HS6 carbs as these have a different choke arrangement, however I've had similar issues with my TR4's H6 carbs in the past. Rich running is sometimes caused by one or both jets not returning fully home after using the choke. I fixed the issue on mine by polishing the outside of the jets (I held them in a drill and used fine steel wool soaked in polish). When I first got the car I had one jet that was particularly sticky. Turned out it was slightly bent and replacing it (and polishing it) solved this problem. Steve Quote Link to post Share on other sites
John Mellor Posted February 13 Author Report Share Posted February 13 Thanks Steve, should have said I have a TR4 sounds a good idea to look at that. Did you replace the gaskets and washers as well. Regards Quote Link to post Share on other sites
Steve Priest Posted February 13 Report Share Posted February 13 Yes, I partially rebuilt my carbs a few years back to fix a leak, replaced seals and fitted new jets and needles. It was after this that the jets started to stick, so I took them out and polished them. You can remove and refit the jets with the carbs in situ without touching the seals, so you could try this first. The seals are fairly simple to replace, but you will need to remove the carbs and then reset the mixture afterwards. You can order any bits you need direct from Burlens. They also have rebuild kits: https://sucarb.co.uk/shop Steve Quote Link to post Share on other sites
BlueTR3A-5EKT Posted February 13 Report Share Posted February 13 (edited) Which carb type? H or HS I did not think there is a seal between jet and jet bearing tube on HS carbs. So the friction is either in the mechanism/connecting lever or the jet is seizing in the jet bearing tube on H type there is a selection of seals These are now subject to modification with modern fuel proof seals. Talk to Burlen. Items 96/97 in the h type image. https://sucarb.co.uk/technical-hs-type-carburetter-hs2-hs4-hs6-dismantling image HS jet arrangements Has plastic jet base and external tube to float chamber Edited February 13 by BlueTR3A-5EKT Quote Link to post Share on other sites
david ferry Posted February 13 Report Share Posted February 13 If any readers are interested, I have a pair of TR4 H6 carbs on a manifold with linkage (I think) looking for a new home. They are currently with my engine builder, and have been sat on his shelf for ages (about 3 years now) as I don't need them on either racecar. There's a final bit of rebuild to finish them off and then they're ready to be rehomed. If interested, let me know. David Quote Link to post Share on other sites
John L Posted February 15 Report Share Posted February 15 I have fitted this kit to a friends MG TD with H SU's in place of the old cork gaskets, has worked well, https://www.ebay.fr/itm/283635227883?itmmeta=01HPNZCFZDAMRMYHX9FC0G02KW&hash=item4209fa1ceb:g:a4gAAOSwDIxdg0bI John Quote Link to post Share on other sites
John Mellor Posted February 15 Author Report Share Posted February 15 Thanks John, this is only 30 minutes away from me Quote Link to post Share on other sites
John L Posted February 16 Report Share Posted February 16 Its good to polish the jet tube with some brasso to make a really smooth surface for the o rings to slide on, and clean the jet holes so they don't cut the o rings when you slide the tube up. The nice thing about these you don't have to change the brass shaped washers. The Burlen kit wants all new parts at a very much greater price! John Quote Link to post Share on other sites
Steven Whitaker Posted February 23 Report Share Posted February 23 On 2/13/2024 at 6:20 PM, BlueTR3A-5EKT said: Which carb type? H or HS I did not think there is a seal between jet and jet bearing tube on HS carbs. So the friction is either in the mechanism/connecting lever or the jet is seizing in the jet bearing tube on H type there is a selection of seals These are now subject to modification with modern fuel proof seals. Talk to Burlen. Items 96/97 in the h type image. https://sucarb.co.uk/technical-hs-type-carburetter-hs2-hs4-hs6-dismantling image HS jet arrangements Has plastic jet base and external tube to float chamber I'll second that. I just rebuilt my HS6'2 and there isn't a seal on the chokes jet arrangement. Mine were 'sticky' as the actuating levers were slightly bent. Once straight they work fine. Hope that helps. Quote Link to post Share on other sites
John Mellor Posted March 2 Author Report Share Posted March 2 Many thanks, after reassembly it was obvious that there is much less friction in the jet movement. On examination the old cork washers were hard and were, I guess, the main culprit; deposits on moving surfaces of carb can't have helped as well. I now have a much easier pull on the choke and a lovely blue flame in the Gunson p!ug and nice rhythmic beat of exhaust on idle. Feeling very smug and desperate for dry weather ( Dixon doesn't like getting his feet wet !! ) Regards Quote Link to post Share on other sites
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