Noob tyring to get in the air K&B .40
 

Good day,

This will be my first post on this forum (or any RC forum), so if there is a FAQ some where and I have missed it, please let me know.

I have a Solo Flight Trainer with a .40 K&B glow engine. I was given the engine and I finally got her cleaned up and "running". I have poked around the Internet and found the manual and some instructions on the K&B engine at www.modelengine.com, BUT..... I cannot get it working to what I think is correct.

SYMPTOMS:

engine idles well and has a good WOT respone but dies out at any WOT for more that about 2 seconds. I can get the plane airborne, but as the engine is loaded with lift off of the plane, it stalls and dies. the engine and prop are matched to the plane and are the recommended size.

WHAT I HAVE DONE:

There are 2 screws that I can adjust (3 if you count the barrel stop).

1. The large needle valve that admits fuel from the tank.
2. a smaller needle valve on the linkage side that adjusts idle(?).

I have the large needle valve open about 2 turns, the smaller needle I have had to turn down to almost closed, I would say about 1/4 to 1/8th open to get the engine to start and idle. this is the setup I have that allows me to start the engine, maintain some semblance of idle speed, but it stalls out on WOT.

I don't know alot about this thing, what I have learned is from looking at the manual (.pdf) and making my own assumptions, don't have any one local (I live on 90 acres in the country), so I am at a bit of a loss right now.

The manual goes into starting and adjusting the engine, the problem, I am not a retard, but they change the names of the two needle valves 3 times during their description so that I cannot determine what valve I should be adjusting......arghhhh!!!

I am using new clean 10% fuel, any help you can toss my way would be appreciated, I am looking forward to one day flying this thing and at least getting it up more that 3 feet off the ground.

Attached is a crude picture of my carb.

Many thanks,
Gunslingerblue

RE: Noob tyring to get in the air K&B .40
 

Buddy, you have some seriosues.....................:)

OK..............K&B's are difficult motors to deal with, some run great and some run like
crap.

The motor will always run rich, it will never run lean. The two needles work together,
sorta. K&B have always been know to run great WOT,, however not idle very well.
You motor is running the other way around. That may be good.

If you can, start with some different plugs, what ever you can find, prefered to be new.
OS, K&B, Fox, H9, McCoy, something. A OS 8 seems to always work for me in any
motor. It does not matter that the plug may be new, just try a diffent plug.

Open up the high end some, not a lot. You are describing the high being lean. If the
motor will idle for any length of time, 30 seconds+, you have the bottom in the right
spot.

If you get the peak RPM at the top, it will be to lean on the bottom stay running,
leave the top (WOT) rich.

Just keep working with, they all run rich, none run lean.

Push come to shove, spend 50 bucks. In either a OS 40 or in gas to go to a flyn field,
even if it is a few hours away. These planes are too much fun to be agravated with a
motor.

RE: Noob tyring to get in the air K&B .40
 

Hey, YNOT. I think you're the same guy that I e-mailed about teaching me how to fly at Escobee. I just saw your signature Tony D. Cool.

RE: Noob tyring to get in the air K&B .40
 

Thanks Ynot,

I think I can narrow it down to the "big" needle valve, just have to spend more time on my knees, then when I am done praying....I can mess with the engine :).... will post back my results......

RE: Noob tyring to get in the air K&B .40
 

I'm not sure about this, but here are my thoughts.

If you didn't mention the low speed, I'd say you are too lean by just a bit, which is causing the engine to slow and die.

However, the low speed and high speed settings do interact with each other. I think you have the high speed too far out, too rich, and that you've closed down the low speed too much to compensate, which makes the low end run ok, but the high end is erratic. I'd try to put the lowspeed screw back close to the factory setting, and adjust the high end, starting a bit rich and working inwards. Some engines do not run well rich, they don't do the blubbering 4-stroke thing, they just spit and die at full throttle.

It's also possible you need a different glow plug, likely a colder plug. If the plug is too hot, the enigine pre-detonates at high power, and run poorly or stops.

Once you get the engine running at full throttle, you can try to slow the engine down and see if it will idle and transition. If it won't, you can adjust the low speed screw in very small increments, no more than 1/8th of a turn at a time. Every time you adjust the low end, you need to re-tune the high end at WOT, and then test the idle and transition again. Setting the low end is a time consuming process, no question about it.

Also, you can't really set the low end until the engine has had some run time on it, as the engine's performance changes a lot at the low end, which results in a different "best" setting.