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Weber 38/38 DGAV


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Is there a jet/tubes set up that works best on a stock

8.3:1 M10

The motor is fresh and runs great with a 32/36.

But with the 38 it runs crazy in the upper rpm's

and has a flat spot around 3200-3500.It idles fine at

900 gets out of the hole fine and after 3200 goes like hell.

Right now there are 145 and 185 jets in it I'm not sure about

the emulsion tubes.The idle screws are out @1 turn.

Thanks for any help

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My guess is you are lean at some point in the operation of the carb.

In my limited self taught experience based on twin 38/38 on a CS is that the idle circuit effects 0-2500rpm, mains 2500 - 4500rpm and air jets to redline. The range of effects overlaps the jets but in general its a starting point on where to makes changes. Change on thing at a time. A fuel air ratio meter is also very helpful.

Generally the 38/38 stumble occurs at the transition from idle circuit to mains at around 2500rpm. That symptom can mean that your idles are to small and you have a lean condition that cause you to rely on the mixture screw to minimize. Mixture screw less 1 turn, idle screw less then 3/4 and engine idle speed should be fine at 750rpm.

Your problem sounds different given the flat spot is around 3200rpm but you have great performance above 5000 which is typically where the 38 drops off. Guessing this is where you are lean. Try increasing the main jet by one half size. If it improves but still exists go up another half size. etc etc

If this is working and you are pretty happy with the results then increase the air jet one size and see if there is an improvement. If it gets better then increase another size. Etc etc etc

76 Sahara 2002

73 CS Polaris

84 Tucker Snocat!!!

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searchy searchy searchy...

your 'transition' jets are lean. We're not 100% sure, but bigger than 50

seems to be a general consensus...

and you have to searchy to find out what I mean by transition jets...


"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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