simon67 Posted December 4, 2004 Share Posted December 4, 2004 I've been looking at some old postings on setting up the carbs on a VX 2.0. I've got a low revs flat spot & feel that there's a lack of sparkle at low/medium revs. It sounds like I need to change chokes, idle jets etc (according to Roger King post). Firstly has anyone else done this & what kind of difference has it made? - I'm looking for driveability & grunt rather than top end power. Secondly, can you recommend anyone to carry out this work in the S/E? Has anyone tried East Kent Carbs in Ashford? Any info gratefully received Cheers Simon '91 VX HPC making lots of noise in Kent Link to comment Share on other sites More sharing options...
I reply to every thread Posted December 4, 2004 Share Posted December 4, 2004 Try Redline in Caterham or Gerald Dale in Hastings/St Leonards Link to comment Share on other sites More sharing options...
stevefoster Posted December 4, 2004 Share Posted December 4, 2004 I tried 38mm chokes and different jets and 3d mapping. It was nice on the road. Then I raced and went back to the 40mm chokes and original jetting, I fancied it gave a bit more power top end. Finally I fitted Jevey's (45mm chokes) and the through the bonnet race exhaust. That's a big jump up. Not original and O/T but that's how she'll be staying for quite a while. Chokes and jets are pretty straight forward to do yourself if you are following someone elses recs. If its not right i.e. big flat spot then it would be worth seeking a decent Rolling Road chap. Hants (North) and Berkshire Area club site here My racing info site here Link to comment Share on other sites More sharing options...
StewartG Posted December 5, 2004 Share Posted December 5, 2004 If you let it be known what chokes and jets you have at the moment I'm sure someone will be along with recommendations. Link to comment Share on other sites More sharing options...
simon67 Posted December 5, 2004 Author Share Posted December 5, 2004 Stewart, I am guessing that I have the 'standard' factory setup - 40mm chokes, 170 main, 50f6 idle, 180 Air corrector and F16 Emulsion. I'll do some checking tomorrow though. The 'feel' of my car does suggest that the setup is a bit off ideal. Simon '91 VX HPC making lots of noise in Kent Link to comment Share on other sites More sharing options...
Don Cook Posted December 5, 2004 Share Posted December 5, 2004 I've got 48 DCOSPs with 42 chokes for track and 38 chokes for the road. There's a terrible flat spot at below 4000 with the 42 chokes but no problem at all with the 38s. I think you lose about 10 horse vat bthe top with 38s. Link to comment Share on other sites More sharing options...
StewartG Posted December 5, 2004 Share Posted December 5, 2004 Simon I would say the chokes are too big, for the road 36 or maybe 38mm will give much better driveability. You may also be describing a progression type problem ie a hesitant pick up between idle and say 1500ish rpm. This can be improved by either extra progression holes or perhaps the Bill Shurvington method of adjusting the closed butterfly position not to give correct idle speed but so that the first progression hole is uncovered as soon as the butterfly moves. I haven't tried this as I don't have the required ability to trim the idle speed via the ignition advance but I can report major improvements with extra progression holes. It's fairly common knowledge that Caterham's carb set-up was not ideal and significant benefit comes from different jets and 3D ignition. Iwould suggest a call to QED, they will give you their recommendations for your engine spec, they know these engines and carbs, it won't be far out. Link to comment Share on other sites More sharing options...
simon67 Posted December 6, 2004 Author Share Posted December 6, 2004 Decided to let the experts set up my carbs with smaller chokes etc after toying with the idea of doing it myself. I don't want to make a balls of it and then have to go to get it put right with my tail between my legs! I'm going to try Race Power in Northfleet, they have a rolling road and a guy that seems very clued up. He even claims to have set up Chris Rea's 7 recently! Anyone got any experience of them? Cheers for the advice Simon '91 VX HPC making lots of noise in Kent Link to comment Share on other sites More sharing options...
Bill Shurvinton Posted December 6, 2004 Share Posted December 6, 2004 If you find a rolling road that can actually tune progression let everyone know. 95% of them seem to not do a very good job any one. If you have problems under 3000 RPM you are in a region where a rolling road is not actually much use. If you were closer I would tell you to swing over and let me have a look. Bill Link to comment Share on other sites More sharing options...
simon67 Posted December 6, 2004 Author Share Posted December 6, 2004 Thanks for the offer Bill - pitty I'm so far away. I'll see how they get on with changing the chokes etc & report back. If it's still flat I might take you up on your offer & have a long blat across to sunny Hampshire Cheers Simon '91 VX HPC making lots of noise in Kent Link to comment Share on other sites More sharing options...
ian balson Posted December 7, 2004 Share Posted December 7, 2004 Simon, YHM. Very happy with my RK Carb setup. Rgds Ian Link to comment Share on other sites More sharing options...
Peter MarieEa Posted December 8, 2004 Share Posted December 8, 2004 For improved driveability below 3000 rpm the smaller 38mm chokes are the way to go. '94 HPC Quick7 Link to comment Share on other sites More sharing options...
simon67 Posted December 15, 2004 Author Share Posted December 15, 2004 Have just ftted 38mm chokes and associated jets. Job took about 1 1/2 hours and was pretty straightforward. Initial impressions after a quick blast are that it's a lot smoother and more responsive low down and the power delivery is much more linear. I guess that there's a little less grunt at the top end but I can live with that. The flat spot at low revs has completely gone now! I'm glad that I had a go myself & didn't pay someone to do the work for me. Cost of parts was about £120 inc' VAT and delivery Thanks for the advice Simon '91 VX HPC making lots of noise in Kent Link to comment Share on other sites More sharing options...
Bill Shurvinton Posted December 15, 2004 Share Posted December 15, 2004 I wonder if I should discuss having a carb workshop for one of the shoulder of mutton meets where we can sit around and prod carbs with the free chips. Link to comment Share on other sites More sharing options...
stevefoster Posted December 15, 2004 Share Posted December 15, 2004 You'll have to the join the club soon Bill Carb's won't respond to prodding with chips. It's fettling they need. Thottle B's respond to better to chips 😬 Hants (North) and Berkshire Area club site here My racing info site here Link to comment Share on other sites More sharing options...
Bill Shurvinton Posted December 15, 2004 Share Posted December 15, 2004 Well that's why you never got your carbs right. Everyone knows that chips are required to make carbs work properly. Join the club? Why on earth would I do something like that? More likely that I'd buy a round :-) Link to comment Share on other sites More sharing options...
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