How to make a Carburator

[zeusrekning]

Can someone point me in the right direction on information on how to build a carb. I have had little luck so far but I figured someone here would surely have some info. Carb size is not so critical now. I'm just trying to gather info for carbs on model engines all the way up to bike motors.
Thanks
Tim

 

[kf2qd]

The simplest carb is a rotating barrel type carb as used on many model airplane engines. K&B Had one of the simplest - the needle valve came in from the opposite end the the barrel was inserted from, there was a slot that engaged with a screw that functioned as the idle speed screw and also kept the barrel in the carb. then there was another hole that let bleed air in at the idle setting to keep the engine from running too rich at idle. Will have to dig out my K&B .35 and take a few pictures of the carb.

 

[zeusrekning]

I would really appreciate that. I may need to go buy a carb and reverse engineer it.
Tim

 

[Circlip]

Don't forget that before the Barrel type Carb there was also the Butterfly valve type ;D Ian.

 

[zeusrekning]

Explain, Ian.
Tim

 

[Bogstandard]

Tim,

When I have time, I have a lovely set of drawings for a small barstock carb. I will scan them for you.
The problem is locating them.

John

 

[Circlip]

A disc mounted across a shaft in the bore of a tube, Like on the drag racers, you see them in the large air intakes.

 

[kf2qd]

But for a small carb - a butterfly is a bit more difficult to build. And the earliest carbs were nothing more than a simple venturi and spraybar. Ignition on or off to control speed - like the hit & miss engines and the LeRhone Rotary.

 

[zeusrekning]

A disc mounted across a shaft in the bore of a tube, Like on the drag racers, you see them in the large air intakes.

Oooh! Yeah I get that. I was over thinking your reply I guess. Air supply isn't my issue. I can figure that out ok. It is fuel delivery, jet sizes and placements, and all around design I am needing help with. All of the carbs I have laying around are the butterfly valve. It's just everything Is so small as far as trying to reverse engineer.
Thanks,Tim

 

[raym 11]

Bob Shores designed a carb in 2002 he sent me a drawg. but it is copyrighted.
It is sized for.625 to .750 bore engines. You might try his web site and ask his wife about it.

Ray

 

[cfellows]

Here's a simple drawing of a carburetor I just built for a 2 cylinder, 1" bore, 4 stroke engine I'm building. It's patterned after several carburetors I gotten from other engine projects. Don't know if it'll work, yet, but I have every reason to think it will.

Chuck

 

[zeusrekning]

That helps alot Chuck. So the trottle lever moves the screw?
Tim

 

[raym 11]

Tim and Chuck ;
I finally finished the Ridders foam carb I mentioned on another thread. It runes my 1.2 bore hit and miss well with adjustments to air mix while running. The same for the twin. Jan says the carb was designed for 10 cc and smaller engines.
It is really a neat and clean way to aspirate

The drwg and instruction can be downloaded from his site.
Ray

Jan Ridders
E-mail Address(es):
[email protected]

 

[AllThumbs]

This set of free engine plans has a carb that works. It's a simple venturi and it ran my Webster engine ok. I later modified it to a rotating barrel type.

http://home.comcast.net/~webster_engines/Plans.zip

E

 

[cfellows]

That helps alot Chuck. So the trottle lever moves the screw?
Tim

The throttle lever turns the barrel that extends all the way down through the carburetor body. The screw, the barrel, and venturi tube on the bottom all turn at once when you adjust the throttle. At full throttle, the hole through the side of the barrel is in line with the opening that goes all the way through the carb. As you close down the throttle, the hole in the barrel gets turned more and more sideways which shuts down the air passage. The gap between the needle (screw) and the venturi doesn't change with different throttle settings on this design. However, you might have to adjust the screw separately as you change the throttle settings. This type of carb is meant more for constant speed engines. Better carburetors simultaneously lift the needle away from the jet as you open the throttle. Better carburetors also have another adjustable needle valve that lets you adjust the amount of air in the mixture. This is called the idle jet and is often found downstream from the main or high speed jet.

I know this is probably all very confusing without better pictures. Unfortunately, there doesn't seem to be a lot of information on the WEB, that I can find anyway.

Chuck

 

[dave e]

I don't have personal experience with it, but I read in another post somewhere that it works well.

http://www.jerry-howell.com/H2-Carb.html