That Radial Engine Sound – Saito 33R3 Break-In

I could listen to that “lumpty lump” idle all day.

I finally got a chance to get out to the field and run in the new Saito 33R3 I obtained from Tower Hobbies over the summer. As many of you know, this motor is going to go in my 1/4 scale Seagull Models GeeBee Z. I mounted the new Saito in my test stand, prepared some 15:1 Redline Oil to 91 Octane Unleaded and headed to the field.

The Break-in Process:

According to the manual, you should run the engine at a very rich setting for the first few tanks. I bolted on an 18×10 Falcon Civilian Propeller, set the high needle where it stated for a starting point and gassed her up. I flipped the switch on the ignition, opened the throttle to about 25% and hit the spinner with my electric starter. It was 3 seconds and the Saito was running like a champ. I opened the throttle to 100% and the tach showed about 6400. I then started screwing the high needle out until about 2500 RPM and let it run on he 14oz tank until empty. I filled her back up and ran another 14oz tank through 3 more times. The exhaust was wet and rich and messy as you can see from the picture above! I checked the temperature of each cylinder with my laser temperature gun and the temp never got above 135 Degrees F.

Once I had run 4 super rich tanks through the motor, on the fifth tank I started screwing the needle in until the RPM’s peaked at about 8100 RPM. Did I mention that she was starting easily by hand at this point? I ran the throttle up and down for the remainder of the 5th 14oz tank. I had now run about 1/2 gallon of fuel through her. On my 6th tank I ran her up to 8400 and backed her off to 8200 and let her run at full throttle for a minute, then throttled back to 2500 for a minute, checking the temperature and she was never above 160F. I repeated this for about 10 minutes and another 14oz. On the 7th tank full I ran her at full throttle and was peaking at 8700. The break-in had allowed her to gain a little over 2000 RPM on the top in. I ran her at full throttle for about 3 minutes and then dropped her down to an idle. She was purring like a kitten at about 1000 RPM for the remainder of the tank. I put another tank (#8) through her and I let her idle at about 1200RPM for 10 minutes.

Setting the Idle

Unfortunately the low idle screw requires a super long and skinny screwdriver to adjust and the combination of my test stand and the exhaust ring made it even more difficult. Thankfully, Amazon didn’t disappoint and I had one the very next day. This time I started the engine and was checking my throttle response. I would get it idling and then hammer the throttle full open. If it gurgled and sagged I would turn the low needle clockwise to make it leaner. If it died, I would richen it. It wasn’t long until I had a fantastic throttle response and the following idle in the video below. Click on the link to hear for yourself! If you listen closely, you can hear the rockers and bearings rattling along.

As you can tell, she is going to sound awesome in my GeeBee Z! The exhaust notes are courtesy of the Keleo Exhaust Ring. I can’t wait to get her installed and running that Gee Bee around the Pylons at the field! Once the idle was set I slammed her to full throttle and started tightening up the high needle. Once she peaked, I backed her off about 4 clicks and she never sagged. This 33CC Gasser is going to be awesome!


  • Been flying R/C since 1993. Building balsa airplanes since I was a kid. I love warbirds, aerobats, and just about anything that will fly.

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