correct jets for weber 34datr carb

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x19inspotsy

Low Mileage
got a used 34 datr which I rebuilt, has 50 idle, 110 main with 185 Air corrector in the primary and 50 idle, 120 main with 175 air corrector in secondary. Just installed this carb with an A400 cam, starts and idles fine, but when quickly accelerating she stumbles then revs up. It also does the same at high rpm when the secondary kicks in. Any suggestions? Possibly incorrect jet and air corrector combo?
 
x19inspotsy said:
got a used 34 datr which I rebuilt, has 50 idle, 110 main with 185 Air corrector in the primary and 50 idle, 120 main with 175 air corrector in secondary. Just installed this carb with an A400 cam, starts and idles fine, but when quickly accelerating she stumbles then revs up. It also does the same at high rpm when the secondary kicks in. Any suggestions? Possibly incorrect jet and air corrector combo?
Click to expand...

The stock jetting for the 34 DATR on a European 1500 is (quoting a post in a German forum that Ulix pointed me at a while back) is:
primary: idle 47 main 107 A/C160
secondary: idle 70, main 130, A/C 150.

If that's correct, then your secondary idle is too small, perhaps enough to explain the stumble-and-recover when the secondary opens (the secondary idle jet feeds the transition circuit).
The stumble on initial hard acceleration might not be jetting: ineffective vacuum advance or a weak accelerator pump would also cause that behavior.

Check the archives of the old xweb, as there's a bunch of posts there about jetting for the 34 series carbs. You might also want to drop xweb user tomnj a line - he just installed a 34 DAT.
 
if you want a bit more power and no hesitation its common to change the jets to 120 and 135 this gives an extra 6bhp,this has been proven through rolling road tests :) pete
 
34datr jet sizes

Pete,

I may try bumping up the main jets as you suggested, what air correctors do I use? follow rule of thumb + 40 over main?
 
Fixed the stumble on acceleration

Replaced accelerator pump and associated nozzle/jet ( robbed them from other spare carb), installed stock idle jets and air correctors, bumped mains to 120 & 135 as per Peters suggestion. This car now pulls great, the cam and carb upgrade was worth it. Gentlemen Thanks for all your advice!!!
 
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