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Old May 17, 2010, 07:11 PM
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How do i tune a K&B 40 engine

I recently bought a used Hanger 9 trainer. All the servos work and it will start but I cannot tune this engine for some reason. It spits fuel out of the exhaust(brown colored) and I don't know if this is normal or not as this is my first gas plane. I have followed all the tuning advice I can find online and was wondering if there is something I can do to see if this engine is just a bad engine or if it is salvageable. Any advice is appriciated.
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Old May 17, 2010, 07:34 PM
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United States, FL, Lakeland
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Do you know how old the engine is? All glow engines will have oil coming out of the muffler; the amount depends on how rich the engine is running. It looks like K&B has a couple of different .40 size engines. I just googled them and found an owner's manual for one of the models on their website. Can you tell us what specific problems you are having tuning the engine?
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Old May 17, 2010, 08:16 PM
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The engine is roughly 15 years old but supposively has low hours on it. The compression seems ok. It will start and run. The engine will either idle well or I can get it to run at full throttle well...but not both. The transition to full throttle and back to idle is terrible either way I can get it to stay running. It doesn't seem to have a low idle adjustment screw only an adjustable air valve on the carb and the high rpm mix screw.....even if I completely shut the mix screw it doesnt seem to lean out much.....very confusing to me because I can fix about anything with an engine on it.
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Old May 18, 2010, 03:29 AM
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New Bedford, Ma. USA
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if it's a airbleed carb it kind of works backwards because your adjusting the air and not the fuel, turning the screw out will lean it and on a regular carb you screw it in to lean it, Sounds like it's really rich on the low end.

Dauntae
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Old May 18, 2010, 08:35 PM
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ok....i'll see how that goes....I've got a guy thats gonna try to help me tomorrow that does nitro rc cars.....he thinks the engines should be similar and he has worked on K&B before. I'll just make sure he knows to richen up the fuel a little so it doesen't lean out too much while flying. Any other advice on tuning would be most appriciated though as I am very new to the gas world.
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Old May 19, 2010, 03:09 PM
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Does it have a Perry carburetor on it? Many had them and I think it was the supplied carburetor from the factory later on. Looks like this:
.
If so the idle mixture is controlled by the brass disc.

I had many K&B .40's for R/C and free flight,, they are easy to tune and are great running dependable engine. They will take a lot of nitro too. We used to run them on Class C Free Flights with open intakes (no venturi), pressure bladders on 70 % nitro turning a 10-4 prop at about a gazzillion RPMs.
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Old May 19, 2010, 06:02 PM
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Everett Wa.
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Brown oil out of the muffler is a bad sign. It indicates rusted bearing.
There where three popular R/C carbs that came on the K&B 40 (model # 8011 and 4011) the 8011 had the Perry carb shown above it was a great carb but the fuel metering slot was not self cleaning. If the engine does not respond well one might have to clean the fuel slot in the metering disk with a dollar bill. The Perry carb tends to run rich in the mid range on mid to low nitro fuels. I find the the disk need to be rotated so the indication line on the carb body is pointing to the (-) side of the metering disk and next to the disk indication slot.

The next style carb was first introduced in the 4011 it was a rather large squarish carb. This was a true twin needle type (I liked this carb a lot). And the last style was a rather small looking cast carb that used eccentric cam (screw). I found this to be the less desirable carb.

This site might help
http://www.mecoa.com/kb/parts.htm
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Last edited by Konrad; May 19, 2010 at 06:33 PM.
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Old May 19, 2010, 08:16 PM
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Its definately not the perry carb....It is a large square carburator with a smooth disk near the fuel inlet that has a screw that moves the disk at the top of the disk. Someone told me I need to zero this carb and fuel needle to properly tune it.....how do I do that?
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Old May 19, 2010, 09:01 PM
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Everett Wa.
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Quote:
Originally Posted by jjbd_1409 View Post
Its definately not the perry carb....It is a large square carburator with a smooth disk near the fuel inlet that has a screw that moves the disk at the top of the disk. Someone told me I need to zero this carb and fuel needle to properly tune it.....how do I do that?
That sounds like the last type
http://www.mecoa.com/kb/carbs/carbsptstr.pdf
Just turn the eccentric so that it is centered upwards yet still allows movement 90 left and right. If it binds in the right hand direction back of the screw 1 full turn and recenter.
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Old May 21, 2010, 06:20 PM
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I put a perry carb that came with it on the engine and it seems to be running good now....it has the disk but it doesn't have the thing on the other side of it(looks like a thumb dial or something) what is that for?
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Old May 21, 2010, 07:29 PM
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Everett Wa.
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That disk is the idle mixture adjustment. And yes it is thumb (finger) adjustment.
I thought I read that the carb that came with it was NOT a Perry.
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Old Jun 21, 2010, 08:34 AM
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cessnajfb's Avatar
Springtown, Texas
Joined May 2005
257 Posts
I have an inventory of these Perry carbs if anyone needs one.

Frank



Quote:
Originally Posted by Leadchucker View Post
Does it have a Perry carburetor on it? Many had them and I think it was the supplied carburetor from the factory later on. Looks like this:
.
If so the idle mixture is controlled by the brass disc.

I had many K&B .40's for R/C and free flight,, they are easy to tune and are great running dependable engine. They will take a lot of nitro too. We used to run them on Class C Free Flights with open intakes (no venturi), pressure bladders on 70 % nitro turning a 10-4 prop at about a gazzillion RPMs.
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Old Aug 04, 2010, 11:48 PM
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USA, IN, Evansville
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I need a couple of Perry carbs for my K&B 40's.....do you still have some available
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Old Aug 05, 2010, 04:06 PM
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Springtown, Texas
Joined May 2005
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Quote:
Originally Posted by jrichardj View Post
I need a couple of Perry carbs for my K&B 40's.....do you still have some available
I still have an inventory of the Perry Series 80 Standard Carburetors by Varsane.

The barrel id is 7/16"
The neck od is 9/16"
The neck id is 11/32"

Frank
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