Gbee

I own a R-120GP I bought new about 10 years ago. I use an APC 15 x 8 prop with Byron 15% 4 cycle fuel and Enya no. 3 plug. I have the air bleed fuly open (idles good) and still suffer from rich midrange. I have the needle valve open about 3/4 to one full turn. During the cold weather (20 degrees F) I have to open the needle another 1/2 turn or so to keep. Now the midrange is too rich and the engine quits at about 1/2 throttle. (2 deadstick landings today) My questions are:

What is the correct setting of the pump pressure valve? Should I be able to blow through it (by mouth)? Should I try reducing the pressure?

Should I drill the air bleed hole larger? What size drill?

This is not a new problem, I just started flying this engine in the cold weather - runs much better in the summer (still a rich midrange, but doesn't kill the engine).

Thanks for your helf Jeff. I realize it's hard to diagnose from an email.

MRC-Hirobo-OK-Enya

The main needle sounds right, but the low end does not. That sure seems lean.

Try backing the pressure screw off by one turn as it states in the instruction sheet. If you do not have that sheet, let me know and I can email it to you.

Makes sense to try there first.

Thanks

jeff g

Gbee

Thanks Jeff. I have the instruction sheet, although I haven't looked at it in years. Has it been updated?

Is the pressure valve adjusted by just trial and error, or is there a measurable pressure in psi I can set it to? I recall the instruction sheet had the pressure in metric terms.

MRC-Hirobo-OK-Enya

Yes there is a measurable value that is in metric. Do you need me to convert it for you? IF so let me know, All i have is the metric value. I'll see if I can get you any more starting info.

However, right now since it is running so rich, I would back out the screw 1 turn and see if that helps it. If not go one more and just keep track of the settings.

Jeff G

Gbee

Jeff,

Yes please, convert the metric to psig (pounds per square inch guage). I will try backing off by 1 turn.

Thank You,
Vinnie