Prop selection to match.
 

Hey guys,
Can someone guide me in the right direction in selecting a prop.
I have a .61 FS 4c (older model) that I bought years ago with a 13-6 prop attached to it. The engine is having problems at low iddle, so it has to be runned at the high end of the iddle and this is a bit too fast. The Giles 202 50 size that is mounted on wants to fast taxi and even the approaches are kind of fast at this setting. But if I briring the iddle any lower is not reliable and shuts off.
Can the prop be slowing the engine down at iddle enogh to cause it to shut down? The adjustments to the air screw have been set at the best performing setting already. It runs ok at low iddle as long as the glow starter is connected, when removed the low is rough and not stable. It even seems that the prop brings the engine to slow down rather fast when coming out of full power to iddle. The fuel used is the 15% green fuel that was recommended by the hobby shop (same I use for 2 stroke) Can this be causing the problem?
If a prop is the best bet, what prop would be ok for this engine size?

Thanks in advance for responses.

HM

RE: Prop selection to match.
 

G'day Mate,
First thing, have you changed your glow plug? I use OS Type F, in my 4 strokes.
Next the prop should be Ok, but make sure your idle mixture is set as lean as it needs to be, to run the motor, don't leave it a "bit rich", when you use the pinch test, it should pick up revs very slightly, before cutting out, this may make a difference, try it & see.

RE: Prop selection to match.
 

Hey alan0899, thanks for the reply.
Changed the plug to a new one (F type) after experimenting the same problem with the old one.
As far as I can tell (have not yet done the pinch test and will do it) I have it as lean as can be. The engine dies if I go any more to the lean side (this engine lean is screw out, counter clockwise).
Now the prop does seem to be holding the engine some from full to iddle. Is not as smooth, but it slows down rather rapid. This is why I thought the advice to change prop to 13-4 was ok.
I appreciate any comments, thanks.

HM

RE: Prop selection to match.
 

Your prop is not the problem. Although wood ones are lighter and plastic ones have a flywheel effect. Have you checked your valve rocker arm gaps lately ?

RE: Prop selection to match.
 

The prop I am using is wood. Will switch to plastic though. The valve clearance was adjusted, but will recheck and post. Thanks speedster1919.