Hi I'm breaking in a 120 SP and have some questions. I've run four 14 oz tanks of 10% Omega fuel through the engine in 15 minute intervals. I ran it mostly around 2500 RPM. Now I'm trying to tune the engine to run right and ran into some trouble. The engine will die below 1900RPM without the glow driver. It transitions quickly and smoothly to full throttle, about 5000RPM, but then bogs down to 4800RPM. I turned in the High Speed needle in increments until it is only 3/4 of a turn before it bottoms out. I also turned in the low speed needle 1 full turn in 1/4 turns. I'm using an APC 15.75 x 13 3 blade prop.

I've never heard an RCV engine before, so I don't know how it is supposed to sound, but it doesn't sound smooth to me. It seems to change between two sounds, a whirring sound, and then it goes to a deeper tone, like a governer bouncing back and forth on a lawn mower.

Sound like you have a fuel feed problem. Do you have your tank mounted properly?

You may be running it rich on the top lean it out till it bogs then richen quarter turn then back off throttle and fine tune low speed which should be set at 1 1/2 turn to start.

I forgot to mention that I'm getting a reading of about 145 F at the glow plug, and a reading of 225 f at the exhaust elbow. I'm using one of those laser pointer thermal guns, I'm not sure how accurate they are, expecially on shiny surfaces. Are those good temperatures?

Below is a video of the engine running: Click here to watch Throttle up
Here's another: Click here to watch walk around

Is it possible the 15.75x13 prop is not giving enough flywheel action to keep the engine running at low rpm? Are there any other 3 blade props you would recommend? I can't go much larger than 16 inch diameter.. I got the max RPM up to 5000, and flew my airplane for the first time. The plane is designed for a 90-120 4-stroke the RCV just barely got it off the ground.

Hi

I am pleased you contacted us. Thanks for the video clip, that really helped a lot.

There definately seems to be something up with your engine as it is not producing the power it should on that prop. It should be more like 5500 rpm so your engine is down 1200 rpm on actual engine speed, which would account for its sluggish performance.
It is also sounding much rougher than it should.

If you could email me ([email protected]) with your contact details and engine serial number we can check if it is covered under warranty.

I look forward to hearing from you
Best regards
Laurenne

I sent you an email.