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Nikki carb choke tubes replacement?

Old 08-08-08, 02:12 PM
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Nikki carb choke tubes replacement?

Source for replacement venturi on Nikki?

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I put this up on the 1st gen website and didn't any feedback. Thought I might try here.

25 years ago some rotary firms talked about modifying the Nikki for additional performance. Some modifications were for the very old IMSA RS class. Other were for the street. One of the things that was done was to press out the stock venturis and press in replacement larger diameter venturis.

Weber as an example have replacement venturis but the few that I have seen and use else where are the wrong length, outside diameter, inside diameter, etc

Does anyone know of a source and part # for a larger inside diameter venturi that will press into the Nikki primary and secondary respectively?

If not, for racing only, I can bore the inside out but I won't get a great shape. Has anyone done this? If so what diameter did you take the primary and secondary out to and what was the result?

Did you use a boring bar?

Did you have any problems?

FYI I have done the booster tabs, throttle shafts, air horns, butterfly screws on throttle shafts, tried venting float bowls, air and fuel changes, etc.

Thanks
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Old 08-08-08, 05:44 PM
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contact sterling. he modifiy's nikki carbs, so does Paul Yaw.
http://www.pbandjracing.com/products.html
http://www.yawpower.com/CompanyInfo.html
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Old 08-08-08, 10:45 PM
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Nikki Carb

I have a Yaw carb. I believe Sterling like Yaw do mill out the primaries. I think they make very good street compromise carbs. For an all out race carb I would like to get a little more CFM flow. That is why I am looking for a larger replacement choke tube. Rotary Engineering used to have them 20 years ago. They went out o business. I just don't know where they sourced them from and what other carb interchanges with the Nikki.
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Old 08-09-08, 08:56 AM
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Do you have any rules that would keep you from running a Weber 48 IDA? That would be the best way to go. Or a Berg 50 which is a copy of the basic layout of the Weber but you can go bigger on the venturis.

The SCCA allows the Prod cars to make the primaries the same size as the secondaries so that is where the most development has probably gone. I have not seen anybody going really big on the venturis in years. The racing rules that are out there now kind of set what you're going to find commercially.
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Old 08-09-08, 04:33 PM
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if he is running IT class then he must stay with the Nikki and he can also modify it if he wants.
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Old 08-09-08, 07:27 PM
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In the IT rules you can't punch out the venturis to be bigger than stock.
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Old 08-09-08, 11:11 PM
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Originally Posted by jgrewe View Post
In the IT rules you can't punch out the venturis to be bigger than stock.
I never said he could do that. I was thinking of mechanical secondaries and things like that.
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Old 08-10-08, 10:48 AM
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Can't do mechanical secondaries either

The OP is looking for more air flow from the stock carb and he's reached the limit of mods without going to new vent's. He seems to be way passed IT specs already which would lead me to think if he has rules, they would allow an alternate carb if they allow bigger venturis.
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Old 08-10-08, 11:11 AM
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Sterling mods carbs for a few race classes, I believe IT and PRO7, but don't quote me. Go to www.sterlingmetalworks.com and send him an email stating what your looking for, and I'm sure he'll be glad to help you. His customer service and support are second to none (ask me how I know) and his craftsmanship is better than most mass produced carbs. Without modifications to the venturi's your not going to get much more CFM out of the Nikki.
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