Hello:
I purchased a new O.S. 46LA about 4 months ago from Tower and have been "running" the engine for the last two months. I am about to throw in the towel and remove the engine and send back to O.S., but wanted to post here first to see if anyone has ideas.
The engine has been inconsistant and will run fine on day, but the next won't. After working out the idling issues (as it won't stay running less than 25% throttle), I thought I had it running correctly, but now it won't develop but about 10,800-11,000 RPM (using a tach) with the recommended 11x6 prop (Airscrew)....I didn't have a tach before, but at times when using OMEGA 15% fuel, it developed more power. I am now using MAGANUM 15% and it ran great for a while but now doesn't develop full power and cuts out at full and half throttle...in fact flying today it quit twice (half throttle and full throttle). The only good news is I am getting good at off field landings (20+) and fortunately I am flying a duraplane so I still have a serviceable airplane. Also, the engine would not run well using BRYON 15%: won't idle, died at half throttle, no power.

Is this engine that fuel sensitive? All the fuel I am using is brand new and yes, I have changed glow plugs (O.S. A3) numerous times and fuel lines and pressure checked the lines and fuel tank, as well as tightened all screws including the one on the back plate (BTW: when I received the engine, almost every screw was lose and I had to grind down the needle valve bracket somewhat in order to get the screw to "bite". O.S. also sent a new valve assy b/c the mounting plastic was broke).

I still notice bubbles in the fuel lines, mainly from the needle valve to the carb (have placed fuel tubing over the valve to ensure no leakage).

Any ideas on why this engine is not developing full power and the other ills?

Thanks

Some fuels just aren't as good as others. Differences in blends, types of ingredients, and so on, can make a BIG difference. Try the Omega again. If your problems go away, then you'll know it was fuel.

Another thing to consider is the fact that the weather changes from day-to-day, and this means that the engine's settings will change somewhat. You have to make sure the enigne's properly-adjusted for that day's flying. Idle settings vary very little, but the high-speed needle can vary a LOT. We've seen as much as a 1/2-turn variance from one day to another, depending upon how the weather changed.

Hi Bax:

Well, I tried this afternoon running OMEGA 15% and no joy...rpms are now less (10,200-10,300) with engine warm and not being shy on adjusting the needle valve......

At this point I think I will go-ahead and send the engine back to O.S., as it appears to be worsen.

Thanks,

Hello All:

I wanted to update everyone on the engine issue.

I sent the engine to Hobby Services and they determined the back plate was cracked, which caused the engine to run to lean. They replaced the cylinder, piston, backplate and carb all under warranty. I am very pleased with the turn around time of Hobby Services (total time out and back about 12 days)

I ran one tank of fuel thru the engine with rich setting per the break-in procedure in the manual and then ran a second tank with setting per break-in procedure. I checked the rpm on the optimum setting and it is only developing about 10,200 with a 11x6 prop........it should be running about 12,000-12,500 per hobby services.


Any suggestions?

well appart from taking htis engine of your palne and converting it to a paper weight, i would advise that you change to a medium(temperature) plug with that high nitro content you should be running a no.8 not an A3 (which is a HOT plug designed for lower nitro content like 5% and below.

if that doesnt work then i think you have a lemon and should
A. scrap it and buy somthing else
B. send it in again and see if they can spot somting else
C. send it in again and ask them to send you a completly new engine

regards
James

When you refer to "optimum" setting, what do you mean? Have you leaned the engine to peak RPM? There is no actual value for the number of turns on the needle valve. You have to find it by seeing how the engine is running. As the engine is run, you can gradually lean it until you reach peak RPM. Two tanks' worth of fuel is not enough to break in your engine. We'd run the engine over a 45-60 minute period and gradually work the high-speed needle towards peak RPM. When the engine can sustain running just rich of peak RPM without much change in the mixture, we'd consider it ready to fly and fairly-well broken-in.

Hi Bax:

Thanks for the response. By optimum setting I mean leaned to peak and then enriched to drop the rpm about 200-300. On the 2nd tank of gas at this optimum setting for about 1.5 minute the rpm was 10,200-10,300.

Are you saying as the engine continues to break in it will develop appx 2000rpm more to get to its ~12,000-12,500 rpm (which is what the Hobby Services techs are telling me the engine rpm should be pulling with a 11x6 prop).......

Best Regards