Gentryman Posted March 1, 2023 Report Share Posted March 1, 2023 Looking for some advice re SU carbs please. My engine will start straight away if I drop some fuel into the intakes but even though the carbs have been rebuilt and both bowls are full it refuses to start. Anyone have any ideas? Thanks Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 1, 2023 Report Share Posted March 1, 2023 do the jets drop fully when on choke , and return fully when off choke check the ign switch is passing current when cranking what engine is fitted , has it got any ballasted coil wiring what spark plugs are you using are the jets set to 3 turns down from being flush with the jet holder ?? has it run ok recently and when did it start the problem are these HS2 1.25" or HS4 1.5" on what engine ?? Pete Link to comment Share on other sites More sharing options...
chrishawley Posted March 2, 2023 Report Share Posted March 2, 2023 11 hours ago, Gentryman said: if I drop some fuel into the intakes Would this by any chance be a pair of SUs on a Vitesse 2L engine? Yup, more context would be really helpful. At a first punt; needing added fuel on cold start (but not on a warm restart) does suggest that close inspection of the choke interlinkages might be helpful and that the mechanism is acting equally on jet and throttle on both carbs. But if this is a fresh installation of newly refurbed carbs then there are quite a number of issues that may have to be picked through (of the non-serious sort). More info please! Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 2, 2023 Report Share Posted March 2, 2023 from previous experiences who did the refurb of the SU ??? and SU on the vitesse spec engine never seem to work out well so are they HS4 or HS6 ??? Pete Link to comment Share on other sites More sharing options...
Stratton Jimmer Posted March 2, 2023 Report Share Posted March 2, 2023 My GT6 which has a Triumph Tune engine has HS4s. Frankly, they are a pain in the £&*! and the choke linkages are someone's idea of a joke. It is as though the SU designers having made a device to semi-control a drip of fuel into an engine suddenly realise they have forgotten to include a choke. Luckily there was a box of old knitting needles lying around so they bent a few and bodged a mechanism to pull them up and down. Get a pair of Strombergs and ditch the SUs. If anyone wants to buy a pair of HS6's with adaptor flanges - I have some! Link to comment Share on other sites More sharing options...
Pete Lewis Posted March 2, 2023 Report Share Posted March 2, 2023 think that sums up the SU experience very well both can do a good job if in the right specification one is engineered and one is less able than good olde Meccano , (That worked ) yes i have avid hate of SU and who got a 2000 with two of the things fitted but they are to the correct spec for the model year and they are trouble free its the mix and dont match must haves that give the troubles Pete 1 Link to comment Share on other sites More sharing options...
Steve P Posted March 3, 2023 Report Share Posted March 3, 2023 Nowt wrong with SU`s if they are setup properly, had HS6`s on my 2.5 Vitesse since 2010, set up on a rolling road and not touched since aside from tweaking the tickover a bit. Steve Link to comment Share on other sites More sharing options...
dougbgt6 Posted March 3, 2023 Report Share Posted March 3, 2023 Except you are forever setting up SUs! Strombergs, just set 'em and go, some time in the next 20 years the diaphragms may split, then your in trouble, but I have a box of NOS spares. So I'm all right. Doug Link to comment Share on other sites More sharing options...
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