Jump to content

Advice required on SU carbs


Recommended Posts

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 ??


Link to comment
Share on other sites

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

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

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 


  • Like 1
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Create New...