Bob338 Posted August 4, 2005 Share Posted August 4, 2005 My S3 Lightweight's running rough. I've set the timing up (light bulb across the points etc), plugs + points ok. There's no adjustment on the carb (Solex), yet it appears to be running very rich. I've rebuilt the carb, plus a replacement one, with new jets etc swapped them both back and forth, no change. Choke appears to work and release ok. Any ideas anyone? Cheers, Bob Quote Link to comment Share on other sites More sharing options...
Degsy Posted August 11, 2005 Share Posted August 11, 2005 It sounds as if it is taking air,the usual reason with a Solex carb is caused by the small o-ring on the venturi.Over time this deteriorates and hardens, the seal holds until it is disturbed but then will not re-seal when carb is reassembled. Quote Link to comment Share on other sites More sharing options...
Bob338 Posted August 11, 2005 Author Share Posted August 11, 2005 Many thanks, I'll have another look at it, although if it's the 'O' ring about an inch and a half dia, I have replaced it with a new one. I've now replaced the inlet and exhaust mainifolds + gaskets, still keeps backfiring. Regards, Bob Quote Link to comment Share on other sites More sharing options...
Degsy Posted August 11, 2005 Share Posted August 11, 2005 Hi Bob I will have another think about it ,am away early tomorrow for the weekend so will get back to you next week. Cheers Degsy Quote Link to comment Share on other sites More sharing options...
Degsy Posted August 16, 2005 Share Posted August 16, 2005 Hi Bob Check that the top of the carb or body has not distorted,it does happen with Solex,but they do have a tendency to run rich,is it black smoking? I assume you have checked/changed points,condenser,plugs,plug leads and HT lead and also distributor cap and carbon brush and spring. A possibility is that the springs on the auto advance in the bottom of the distibutor have weakened,this would cause the symptoms you are getting. Let me know Cheers Degsy Quote Link to comment Share on other sites More sharing options...
Lightweight Nat Posted September 15, 2005 Share Posted September 15, 2005 If it's still doing it, might be worth swapping over to a Weber carb? They're quite cheap from paddocks, and are a: dead easy to set up and fiddle the settings, and b: more economical. I don't know anyone still trying to run a Solex... I know it's nice to keep things original, but Solexes are a bit pants. Put a nice shiny new weber on and it should run like a sewing machine at tickover, if the engines in good nick 8) Quote Link to comment Share on other sites More sharing options...
sean101ryan Posted September 15, 2005 Share Posted September 15, 2005 No, don't go for the Weber, they are crap in this application. They strangle what little top end there is, run lean and can be prone to vapour lock. The only reason they can be described as an economy carb is that anything is better than a knackered Zenith. A recon Zenith carb is the same price as a Weber if you look around. Your carb should be a Zenith 36IV, are you sure yours is a Solex (same company anyway I think) When you strip a Zenith/Solex it's worth rubbing the upper and lower bodies on a sheet of wet'n'dry fixed to a piece of glass. This will remove any distortion and hopefully stop any air leaks. There is also a redundant drilling in the throttle body which causes problems but I'm not sure what one, do a google on Zenith 36IV and you should find some good advice. There is one adjustment on the Zenith, same as the Weber, which is the idle mixture screw. Crank up the idle speed a bit, then screw the mixture in until engine starts to falter. Screw it back out counting the turns until it falters again, screw back in halfway and it's set. One other thought, is there slop in the throttle spindle on the carb? This will also cause rough running as air gets sucked in this way. If you have slop with a new spindle, the carb is scrap although I have got away with taking the slack up by using a piece of feeler gauge. Of course if you want real reliability and better performance, fit an SU carb and manifold from Automotive Components. Mucho Dinero though. Quote Link to comment Share on other sites More sharing options...
Bob338 Posted September 16, 2005 Author Share Posted September 16, 2005 Thanks for that Sean, I've done the usual stuff with the carb, in fact, fitted two rebuilt ones, fitted a new inlet/exhaust manifold, new gaskets, changed the plugs and leads, fitted a brand new coil (£30), timing set up with a bulb across the points etc. There is no mixture adjustment on the carb, and it is the 361V. She starts up well on choke, runs great, then as the engine warms up, starts missing and back firing, something appears to be breaking down as it gets warm, next stop is the condensor (although I have my doubts). Regards, Bob Quote Link to comment Share on other sites More sharing options...
oddball Posted September 16, 2005 Share Posted September 16, 2005 Why do you have doubts about it being the condensor at fault? Always go for the simplest (& cheapest) things first! Quote Link to comment Share on other sites More sharing options...
Lightweight Nat Posted September 16, 2005 Share Posted September 16, 2005 if it was the condensor it probably wouldn't start or fire at all. don't rule it out though, if you can get hold of one, see what difference it makes. are you 12v or 24v? if you can find a source for sensibly priced 24v condensors let me know!!! craddocks wanted £30 odd last time i rang them :evil: money grabbing t***ers! running rough as it heats up and you let off the choke suggests fuel starvation, either by blocked jets or knackered lift pump, or a sticking float perhaps? or over leaning because air is getting in. although with the list of things you've done, i would have thought these bases would have been covered... hmmm... :? Quote Link to comment Share on other sites More sharing options...
Lightweight Nat Posted September 16, 2005 Share Posted September 16, 2005 ooh, nowt in the tank is there? just wonder wether theres some crap getting trapped against the gauze on the pick up, which drops off when the fuel pump stops allowing you to start up again, then gets picked up when the fuel pump provides suction. Quote Link to comment Share on other sites More sharing options...
oddball Posted September 16, 2005 Share Posted September 16, 2005 if it was the condensor it probably wouldn't start or fire at all. Not at all, I have replaced more condensors in my time for mis-firing problems than non starting ones. Quote Link to comment Share on other sites More sharing options...
Lightweight Nat Posted September 16, 2005 Share Posted September 16, 2005 if it was the condensor it probably wouldn't start or fire at all. Not at all, I have replaced more condensors in my time for mis-firing problems than non starting ones. fair do's, I stand corrected! I've done 2 condensors and both times it wouldn't even cough or splutter, just spin over on the starter totally dead. Quote Link to comment Share on other sites More sharing options...
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