051 Tee Dee Cloning to a .050 Tee Dee R/C

Background: I’m trying to turn (clone) a .051 TD into a .050 RC
using a new carb. from Bernie. The carb. seems to work fine but I can’t get it to
idle as slow as I’d like. I am using an old standard COX muffler.
The prop is a COX 5x3. Engine runs well but the idle is a bit high 5-6K.
I live at 5000’ above sea level. I would like to get it to idle at 3-4K if possible.

I have several questions which are as follows:

1. Did the .050 TD RC have SPI ? My .051 TD has .004”
of SPI and screams with the normal intake setup.
2. Is this SPI the reason for not being able to get a slow idle?
3. How should the air bleed be setup and is it critical how it
is set for low idling?
4. Could the size of prop. influence idle speed?

astronomer wrote:Background: I’m trying to turn (clone) a .051 TD into a .050 RC
using a new carb. from Bernie. The carb. seems to work fine but I can’t get it to
idle as slow as I’d like. I am using an old standard COX muffler.
The prop is a COX 5x3. Engine runs well but the idle is a bit high 5-6K.
I live at 5000’ above sea level. I would like to get it to idle at 3-4K if possible.

I have several questions which are as follows:

1. Did the .050 TD RC have SPI ? My .051 TD has .004”
of SPI and screams with the normal intake setup.
2. Is this SPI the reason for not being able to get a slow idle?
3. How should the air bleed be setup and is it critical how it
is set for low idling?
4. Could the size of prop. influence idle speed?

you are getting a good idle from that engine i do believe that the engine had spi, i am not sure how much.

if anything i think that more spi would give a higher idle.

yes the prop size will affect the idle a larger prop will give a lower idle if you need that.

but your idle seems fine to me.