David Jackie Ford Posted April 22, 2001 Share Posted April 22, 2001 Hello all. I am a new owner of a 1991 De Dion 1700 X-Flow. Problem - at low revs the twin 40's "spit" especially when cold, but less so when hot. Is this normal or is something wrong? NB I'm using super U/L & Millers VSP. David & Jackie Link to comment Share on other sites More sharing options...
oilyhands Posted April 22, 2001 Share Posted April 22, 2001 Spitting normally indicates that the barrel in question is running weak or the timing is hopelessly retarded, the fact it spits more when cold indicates weak mixture. Weak running could be an air leak or it could simply be that the idle volume screw for that barrel needs adjustment, these are on the top of each barrel near the manifold flange, they screw anti-clockwise to richecn, clockwise to weaken, only adjust them gradually. Oily Link to comment Share on other sites More sharing options...
Pierson Broome Posted April 23, 2001 Share Posted April 23, 2001 As new owners and a 'Novice' on this forum, you might like to consider having your x/f carbs. professionally analysed by Roger King. If you're new to the scene, you may not yet have come across Roger, but as has been stated many times by many folks (me included), Roger has forgotten more about x/f's and Webers than most of us will ever know. Maybe it'll depend upon your location, but a trip to his facilities in Herts. will solve any worries you might have about jetting, mixtures, idle, etc., etc. once and for all. Pierson Link to comment Share on other sites More sharing options...
John Whyman Posted April 23, 2001 Share Posted April 23, 2001 Just to add weight to the mixture argument. My experience in my 1990 XF had and has slightly the same problem. The twin 40's were set up with fairly weak jets (O.K. for touring), but the balance was off.Ear sensitivity to set was not accurate enough. Find a competent person with an air flow meter to get balance right and then only adjustment is the mixture and tickover screws. An 18 yr old lady did mine brilliantly in about a half hour after a crap job with a garage. My other problem was slight over fuelling and float over pressure from a modified fuel pumping system,( Facet electric interrupter) causing popping and general noise. With help from all on here, it was cured by an inline pressure regulator set at 3 psi. 10 min job, but huge difference. Happy motoring. C7 WJW Link to comment Share on other sites More sharing options...
Roger King Posted April 23, 2001 Share Posted April 23, 2001 Assuming that the problem is occuring on very light throttle openings (which is the norm), the answer almost certainly lies in your slow run jets. The problem is very common. At about the time that your car was built, Caterham changed to a richer slow run jet which provided the cure. Without knowing which jets you have in your car it is impossible to be certain, but this is definitely the first place to look. There is also the possibility that the idle screws are set too weak. These screws are fed by the slow run jets, so they may be working together to give the problem. Ignition timing should also be looked at. If you have an 'unleaded' distributor the figure should be 14 degrees btdc at idle. Significantly retarded timing can make the problem worse, but it is usually secondary to the slow run jet calibration. Link to comment Share on other sites More sharing options...
Graham Sewell Posted April 23, 2001 Share Posted April 23, 2001 The problem with using the 'richer' idle Jets 50F9 vs 45F9 is that the spark plugs will foul if you have any town driving at the end of a blat. This can then cause problems with starting.... Cheers, Graham Link to comment Share on other sites More sharing options...
oilyhands Posted April 23, 2001 Share Posted April 23, 2001 Calibration of progression (idle jets) is not an easy thing to master, the jump from 45F9 to 50F9 need not affect the idle mixture since it can be trimmed using the volume adjustment screws but it will affect light throttle driving. Perhaps a 50F8 which has a larger air drilling than an F9 will give you a halfway house. Quite often the progression holes for the critical off-idle and light throttle are not ideal for the characteristics of the engine which means that you have to over compensate with an over-rich idle jet. The first step *has* to be to trim the idle mixture and balance correctly / check for air leaks and see if the problem goes away, if it does.. worry no more, if it doesn't then a change to 50f8 or 50f9 idles might be an idea, you will then need to re-trim the idle mixture. Oily Link to comment Share on other sites More sharing options...
Roger King Posted April 23, 2001 Share Posted April 23, 2001 To some extent it is a matter of pot luck with your idle jet requirement. There are some Supersprints that run OK with 45F9, but most are better with 50F9. The 50F8 does sometimes work too, but tends to run better with milder cams than the 234. In the end you just have to try each one and choose the weakest that is satisfactory. If idle screws are set correctly, we have never seen a (healthy) engine that fouled it's plugs on 50F9s. Link to comment Share on other sites More sharing options...
David Jackie Ford Posted April 23, 2001 Author Share Posted April 23, 2001 Thanks everyone for your help and advice. I would have liked to take the car to Roger King but Hoddesdon is too far from Stoke on Trent. I will try the simpler solutions myself and let you know how I go on. Thanks again. David & Jackie Link to comment Share on other sites More sharing options...
John E Posted April 24, 2001 Share Posted April 24, 2001 Chester is'nt to far from you so try the following, J&J Garage 01244 312695 They are Weber agents and have a rolling road. I'm aware of at least 3 cross flow 7's that are looked after by this outfit. Link to comment Share on other sites More sharing options...
captain chaos Posted April 24, 2001 Share Posted April 24, 2001 My car is tuned by a chap in Congleton which is only 2 stops up the M6 from Stoke. If you want to speak to him mail me and I'll forward his number. Link to comment Share on other sites More sharing options...
captain chaos Posted April 24, 2001 Share Posted April 24, 2001 My man is only at Congleton ( 2 stops up the M6 from Stoke) If you want to speak to him mail me and I'll dig out his number. Link to comment Share on other sites More sharing options...
captain chaos Posted April 24, 2001 Share Posted April 24, 2001 ...Bugger... Link to comment Share on other sites More sharing options...
Andrew Russell Posted April 24, 2001 Share Posted April 24, 2001 If you want to travel in a different direction, you could try John Noble at Chesterfield....Well thought of, a Caterham Agent and not too far away from you. Check on Alex's site for contact details as I don't have them with me. Andrew Link to comment Share on other sites More sharing options...
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