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Discussion Starter #1
er, a tentative hello to the world of technical forums... (i'll jump right in)
my mildly tuned 1750 'nord' goes great - i rebuilt the carbs (2x 40dhla dellortos) last year with proper kit. I've got good even idle at about 800rpm and car pulls strong and clean under load from rest through the revs - so don't want to start messing with current specs too much.
well, my question is that when idling, if you blip the throttle there is a hesitation (stutter) before it revs. If you rev slowly from idle circuit through to mains, there is no hesitation - accelerator pump jets are all working.
carbs are balanced with quality gear and everything burning nicely according to colourtune.
doesn't really affect driving, but doesn't feel right(?)

thanks for any thoughts,

john
 

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Hi,

Concerning my car's project I'm not to this point yet but I would be very interested by the replies you'll get.

I'll follow this. :D
 

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don't trust colortune u have to have a read on what u burn in order to figure out if u r running lean stochio or rich
 

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don't trust colortune u have to have a read on what u burn in order to figure out if u r running lean stochio or rich
Determining whether your are lean or rich is exactly what the Colortune is supposed to do. You look through the glass top of the Colortune spark plug and watch the combustion process change as you adjust the idle air. It always worked for me. I've been using one for years. Also, Colortunes were highly recomment by David Vizard.
 

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well, my question is that when idling, if you blip the throttle there is a hesitation (stutter) before it revs. If you rev slowly from idle circuit through to mains, there is no hesitation - accelerator pump jets are all working. carbs are balanced with quality gear and everything burning nicely according to colourtune.
If you haven't already done this check the jets/venturis of your carbs against factory specs. Then check your ign. timing and make sure it's right. If the carbs are set to standard and the ign. is right the problem should go away. If it doesn't, return to your carbs and check your float levels and accellerator pumps.

If you engine was only mildly modified, the stock carb settings should work OK.

You didn't tell us how the car was running before you rebuilt the carbs. Did it hesitate at that time too?
 

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Discussion Starter #7
thanks folks - was just about to check timing. i'm never sure about the colourtune 'just going blue, but maybe a bit of yellow' reading - it seems this relates to a setting on the carb, give or take a turn, which can affect the set-up quite a bit.
more fiddling over the weekend i reckon!
would anyone have the sizes for idle and accelerator pump jets for a 1750 on dellortos (current pump jet is no.38) i'll check the others
 

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A common problem with carb Alfas - or at least the slightly modified ones - is that many of the favored dizzy advance curves are really fast right at the transition form idle to higher. If you get too much advance, you get the hesitation you mentioned. IF you have a good timing light, watch the advance as you exercise the throttle. You might find that a little less initial advance will help the transition.

Robert
 

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in my opinion, the best results could be taken by having a lamda sensor just after the headers. Seems need a lot of work but on the other hand what says a lamda sensor wouldnt be wrong
 
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