K&B 40 Carb Tuning

[Cherokee996]

Hi Folks, it's me again. I was able to start my K&B 40 Series 8011 and verify that it runs, but my carburetor seems to have some issues. Whenever I pour fuel into the tank and connect the hose, all of the fuel will run down through the needle valve even if it is fully closed. I have cleaned the carb and replaced all of the small o rings, but I need to set it properly again. The only instructions I could find were for the K&B carburetor; my specific engine has the perry carb variant. Any help would be greatly appreciated!

 

[PsyBorg]

Look for worn in rings on the needles showing wear as well. If that is a one needle carb start with like one and a half turns out from a light seating of the needle in fully closed position. Then if no start open it a quarter turn and try again. You may have to go out as far as three turns but I don't remember many and can't think of one that was more then three turns.

Oh yeah and the air opening on the throttle valve should be ~ 1 mm to start when in the idle position.

 

[Cherokee996]

Thanks for the reply! What about the black screw? I couldn't find any info as to what it does and I was wondering why this might be? Is there any setting I should follow? Thanks again!

 

[PsyBorg]

I will assume that is the screw used to set idle by holding the throttle valve open. I will poke around and see if I can get you more info on that specific carb.

 

[Cherokee996]

Thank you so much! I can provide high resolution images of all the parts if it helps. It's just every time I put fuel in the tank, it overflows the carburetor and floods the crankcase.

 

[PsyBorg]

Well that's a first... 4 to 5 turns to start.

Check this out.

http://www.mecoa.com/faq/carb/kbsq/kbsq.htm

This may help as well..

http://www.rcuniverse.com/forum/glow-engines-114/7998292-tuning-k-b-40-w-perry-carb.html

 

[Cherokee996]

Thanks, I already checked out both of those links. I have tiny O-rings for the slow speed unit but I haven't had the time to search my workshop for them. I'm also beginning to wonder if it's the fuel tank. I haven't purchased a nitro tank with the dual tubes yet, so far the fuel has been delivered through a cut off IV drip tube. I didn't think this would be an issue since these engines have been mounted upside down and sideways on aircraft, but would the lack of vacuum pressure from the silencer cause the fuel to overflow the carb?

 

[pipemajor]

Old thread but that's definitely a Perry carb. Idle mixture is the large disk with the reference mark on it. If the seals are good it's a very good carb. Old, leaky o-rings, not so much.

 

[SlingShot]

When you choke it by putting your thumb over the carb and cold turning the motor, it should draw fuel right on into the carb on the first or second turn. The tanks should not be above the engine. It should be level.