KE ping it real Posted February 12, 2012 Report Share Posted February 12, 2012 Hey guys, i have a dillema with my new 40mm dcom weber I bought it from recarb in qld all serviced up, ready to run Got it all mounted on the redline manifold beautifully and then spenmt until 4am this morning trying ti get it to run!!! It came jetted for the 4k, It looks clean as, it idles perfectly and if you bring the revs up slowly it responds but if you snap the throttle, it just bogs down and leans out We suspect the throttle pump but we pulled it apart and it seems to be funtional ANY IDEAS ANYONE????????!!!!! We tested it thoroughly for any air leaks and couldnt find one Its Killing me Please help Thanks in advance Andrew :bash: :bash: :bash: :bash: :bash: Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 12, 2012 Report Share Posted February 12, 2012 When you hold the carb in your hands (off the car) it should shoot petrol clean across the garage if you open the throttle. I think if you look down the throats with a torch you can see the jet of petrol being pumped in too. How did you check it was working? Quote Link to comment Share on other sites More sharing options...
snot35 Posted February 12, 2012 Report Share Posted February 12, 2012 And how do you know that it's lean? Do altezza's check. If that works then it could be the mixture is wrong. Get it on the dyno if you can, otherwise you might want to check how big the accelerator pump bleed is and compare it to other similar engines. Quote Link to comment Share on other sites More sharing options...
ke70dave Posted February 12, 2012 Report Share Posted February 12, 2012 yeah i woudl be curious as to how you know it leans out? also i know its the gineric answer, but have you double checked the ignition timing? and make sure the advance is working? in my experience anything funny with the ign timing and the engine can run fine but feel very doughy with quick throttle changes. Quote Link to comment Share on other sites More sharing options...
philbey Posted February 13, 2012 Report Share Posted February 13, 2012 Have you had it professionally tuned????? Quote Link to comment Share on other sites More sharing options...
corollaart Posted February 13, 2012 Report Share Posted February 13, 2012 These guys are usally pretty good with there jetting. 1:vacuum leaks,check again. 2:fuel pressure test with a gauge.These things are very tempermental. 3:float level 4:just check the idle jet size,as the idle jets work up to 2-3000rpm,or close to. rob Quote Link to comment Share on other sites More sharing options...
philbey Posted February 13, 2012 Report Share Posted February 13, 2012 jetting isnt tuning though. Get it on the dyno and get it sorted out. Quote Link to comment Share on other sites More sharing options...
JDMJared Posted February 13, 2012 Report Share Posted February 13, 2012 These guys are usally pretty good with there jetting. 1:vacuum leaks,check again. 2:fuel pressure test with a gauge.These things are very tempermental. 3:float level 4:just check the idle jet size,as the idle jets work up to 2-3000rpm,or close to. rob Vacuum leaks usually make it very hard to hold an idle but when you open the throttle it will rev fine, He says he has the opposite problem. Float level is a real possibility along with incorrect jets. Can you describe in greater detail what happens when you open the throttle too fast? If it stalls a little at low rpm, struggles and then climbs its probably too rich. If it quickly climbs a little but then cuts off at higher rpm then it is probably too lean. Since it revs fine when you open the throttle slowly i think it is jetted incorrectly and perhaps you should take philbeys advice. Quote Link to comment Share on other sites More sharing options...
KE ping it real Posted February 13, 2012 Author Report Share Posted February 13, 2012 (edited) Wow, Thanks for all the responses guys but i think it was KE 70 dave who had it, IGNITION TIMING :bash: The vacuum on the carb wasnt enough to advance the timing, so it was bogging down We advanced the timing and got it to run much better I still need to downsize the chokes to 30mm (they are 32 at the moment) and i also have some slightly larger main jets and air jets on the way Currently it will now drive under low acceleration but if i try to stand on it or rev it past about 3500rpm it pops and farts and has no pull Downsizing the chokes will richen up all the circuits so i can start fine tuning it a bit AND YES I WILL BE GETTING IT DYNOED PROFESSIONALLY!!!!!!!!!! I just want to tune it/jet it as close as possible to where it needs to be before that stage, mainly beacause i want to learn all about how it works 2 days ago i knew next to nothing about the workings of a weber carb, now i reckon i could feild strip one HaHA The whole point of this car is it is a hobby and i want to learn and do myself as much as i possibly can By the end of the build, i want to be able to take the whole car apart and pout it back together again without issue (not that I'm planning on dooing that though haha) Thats where the enjoyment is for me, Learn by doing Cheers - Andrew Edit - I should also mention that i have a 5k electronic dizzy on the way that i will get properly recurved to suit Edited February 13, 2012 by KE ping it real Quote Link to comment Share on other sites More sharing options...
KE ping it real Posted February 13, 2012 Author Report Share Posted February 13, 2012 A photo.........Its purty :wink: Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted February 13, 2012 Report Share Posted February 13, 2012 Nice! Are you running the dizzy vac off manifold vac? I see a brake boost line going in there don't I?? You could 'T'-piece into there for vac, just do a temporary setup and see what effect it has as the max vac at idle may introduce other problems. Quote Link to comment Share on other sites More sharing options...
snot35 Posted February 13, 2012 Report Share Posted February 13, 2012 32's probably aren't that bad for it given you're running a single Weber. I'm not sure I'd bother changing, just make sure the jetting is spot on. Quote Link to comment Share on other sites More sharing options...
KE ping it real Posted February 13, 2012 Author Report Share Posted February 13, 2012 Nice! Are you running the dizzy vac off manifold vac? I see a brake boost line going in there don't I?? You could 'T'-piece into there for vac, just do a temporary setup and see what effect it has as the max vac at idle may introduce other problems. At the moment , i have the dizzy locked in advance of 20deg and it seems to run a shitload better, took it up a hill to load it and no pinging (i do run 98RON as well) Will probably leave well enough alone at this point regarding the ignition until i get my new dizzy set up properly Quote Link to comment Share on other sites More sharing options...
KE ping it real Posted February 13, 2012 Author Report Share Posted February 13, 2012 (edited) 32's probably aren't that bad for it given you're running a single Weber. I'm not sure I'd bother changing, just make sure the jetting is spot on. Yeah, i decided to give the smaller chokes a go to see how it will change, i can always change back, I have to say that with the 32mm and the timing at 20deg we threw some 150 main jets in it to see how it ran and FOOK ME it flys!!!! It was fouling the plugs, clearly too rich but goes faster then any k motor ive had before!!!! It took any hesitation completely out of the acceleration and it flew, a small flat spot at about 3500rpm but as soon as it past that it revved its ass off smooth and a heap of pull I know that jet size is too big but it definitely confirmed my thoughts about running lean, more fuel changed the whole dynamic of it!!1 EDIT - I should also mention that once i get it jetted nicely i will put up the sizes so someone with a similar engine/ carb can have a good starting point Edited February 13, 2012 by KE ping it real Quote Link to comment Share on other sites More sharing options...
philbey Posted February 14, 2012 Report Share Posted February 14, 2012 AND YES I WILL BE GETTING IT DYNOED PROFESSIONALLY!!!!!!!!!! Haha good O. Loads of people slap on a carb and wonder why it doesnt run correctly. I was of the same mind, fiddled and tweaked, balanced my carbs as best I could but they are the emissions Dellorto's that don't have all the vacuum ports so I just chucked it to the dyno tuner. locked 20 degrees though, that mus really come on cam strong. I never recurved mine and it could benefit from it. Plan is to fit an MSD with adjustable curve control. Quote Link to comment Share on other sites More sharing options...
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