From: goscinsk@sunny.dab.ge.com (John Goscinski)
Newsgroups: rec.models.rc
Subject: LONG Re: tune royal .46
Date: 19 Aug 1995 22:48:44 GMT
Organization: Martin Marietta Information Systems

In article 6c4@enterprise.powerup.com.au, gprice <gprice@enterprise.powerup.com.au> writes:
> I have just bought my first r/c plane and having troubles with the royal 
> 46 engine. It has no trouble running flat out on the ground but soon as 
> it pulls up at any type of angle the motor stalls. As I have only limited 
> knowledge on tuning and thoughts on how to rectify this problem will be 
> much appreciated.
> 


First, I hope you broke the motor in correctly. This would at least
include running a few tanks through the motor with a rich needle
setting. This is not optimum, but would do to get you in the air. If
you didn't, you may have problems getting the engine to be dependable.
 
Now, It sounds like you are running the engine too lean, especially
for a new one. When you are running it on the ground, the tank and
motor are on level and there is no problem. When you pitch the
airplane up, the already lean engine has to pull the fuel up from the
lower fuel tank, against gravity, making it too lean to run.

Here's some advice:

Above all - GET AN EXPERIENCED INSTRUCTOR/HELPER. Otherwise:

Learn to pinch the fuel line. You can tell alot about the mixture that
the carb is set at by pinching the fuel line. You pinch the fuel line
for an instant, one second or less. If you pinch the line and the
engine speeds up, it is rich. If it stays the same, it is at a good
mixture. If it slows down or dies it is much to lean. DO NOT SET IT AT
THE *GOOD* MIXTURE SETTING!!. Since your engine is new, you should
find the *good* mixture setting and then open the needle valve about
1/4 turn too rich. The engine should slow noticeably but still be
putting out good power. You should be able to fly at this setting. Try
a high-speed ground run. If the model seems sluggish, lean it A
LITTLE. Do not force the model into the air, if the engine is too
rich, it will not climb and you could stall it.

Advanced mixture leaning:

Once you have put at least a half-gallon of fuel through the engine
while flying, you will want to start using this method of leaning the
engine to get maximum power while having a dependable engine. Pay
attention, this is how the experts do it.

Start with the engine running rich. Open the throttle and pinch the
line. The engine should speed up then return to its original
setting. Now, alternately close the needle valve 1/16 turn at a time
and pinch the line. When you get to the best setting the engine will
rev-up when pinched, but will not slow back down.

To check that you have a good setting, pull the throttle to idle and
let it settle there for ten seconds. When you throttle back up it
should not rev-up completely, but when you pinch the line again, it
will again rev-up and stay there. So, the engine WILL NOT produce
maximum RPMs when you open the throttle, but will if you then pinch
the line.

Why set the engine this way, you ask?? Because as the airplane gains
speed on its takeoff run, the propeller will create less torque on the
engine and the engine will naturally speed up into the leaner
*pinched* condition. This way the engine is very near max power but
still has the mixture margin to be able to maneuver without dying.

If any of this was not clear please post or mail any questions and I
will do my best to clarify. Sorry about the long length.

John