Air bleed carburetor

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gbritnell

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Gentlemen,
Kel wanted to use a more reliable carb on his newest engine. In his thread he explained the issues he was having with the current one and an idea for using another. A couple of the members including myself suggested using an airbleed type carb both for it's ease of operation and simplicity of build. I posted a PDF file on his build thread but for those who might have missed it I also posted it in the files upload section.
This is the carb I use on my OHV 4 cylinder engine. This size can be used on higher rpm engines up to 1.00 bore. (not hit and miss) It can also be scaled down for use with smaller engines. The air bleed size is not overly critical as the opening is controlled by just moving a screw across the port.
George
 

PhillyVa

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That's very good of you George.....Thanks :bow:

Philly
 

ozzie46

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Thank you very very Much George. :bow: :bow: :bow:

Ron
 

awJCKDup

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Hi George, When you say the carb can be scaled down, is that linear? If you have a .5 inch cylinder, just make the carb airhorn/venturi 50% smaller? I think I've finally got it in my head that smaller is better, I just don't grasp all the scaling.

Thanks
John
 

gbritnell

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Hi John,
Yes to scale it down say by half you could take all the dimensions and multiply by .50. The problem with that is the screws won't scale by half, necessarily. You are right in saying small is better. The slower the engine runs the more air velocity is needed for the best vacuum signal so therefore the smaller the venturi needs to be. The venturi on this carb would seem to be a little large for my 4 cylinder engine and it could probably be made smaller but it runs quite well with it so I never experimented to see how small I could go. I would venture to say that anywhere from .175-.220 diameter should work just fine for an engine with a bore of .750-1.00.
George
 

kcmillin

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FWIW I figure I would post an update for those who want to scale this carb.

I have a 3/8" Bore 1/2" Stroke 4 Cylinder. I scaled the carb down 1/4 of the drawings. I ended up tweaking the dimensions. The barrel has a .067" hole and I have had good luck with this combo, the adjustment screws are all 0-80.

Thanks Again for uploading the Original Drawings George.

Kel
 

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