Checking out a used engine

[Skytrek]

I recently purchased a used Stratus with a Ys 91 already installed. The previous owner indicated the engine is strong but I will like to make sure before I complete the build. Is it recommended to start a nitro while installed in the frame without any kind of load? If there is a good way to test the engine in the frame please give me a little direction.

Currently I have just installed the electronics and the heli is receiver ready. I just hate setting up the head and having to remove a bunch of stuff because the engine is a bust.

Any assistance would be appreciated!!

[mtpenguin]

I would think the tuning stage would be telling. And you can't really tune without it mounted and pushing blades. The biggest part is going from idle to full smoothly with plenty of power and not overheating. I would think if there are problems, it wouldn't tune well.


B-)

[swatson144]

Just by looking through the exhaust port you can easily see if the engine is hammered. Scoring? stuck ring? serious discoloration? Take the back off and you should get some idea of how long/hard the thing was run. If the inside of the back plate looks like an ornate ceiling it may have some other wear. Seeing bad signs on the quick look would indicate not to buy it, but since you already own it..seeing bad signs on those points would be grounds for a further investigation/tear down.

Take the head off and give it a little fuel for lube (in the cylinder). Turn it through and see if it's smooth. If not slosh a little fuel into the crank and let it soak overnight and see if it smoothed out. It'd be a good idea to BDC the piston and look at the liner while you are there! If it's smooth put the head back on and turn it through wet (meaning the ring is lubed but not hydro locked). Does it feel right? Right would be... Turning smoothly until it begins compression stroke it'll get harder to turn as it compresses the air. Turn it on through and it should feel like it was spring loaded. You have enough experience with .50-.90s to know.

While you are at it put some fuel in the crank case and see if it leaks out the front. You'll never get a good tune with a bad front bearing seal.

Most often following those steps will let you know. If the thing don't run well after that I'd be more suspicious of the carb than the motor.

I once changed bearings in a euro/vario spec OS 91 motor because they were "crunchy" turns out that the guy had been using FAI (no nitro fuel) with castor oil. After laying around the dry castor made the bearings crunchy. Once wetted they spun nicely. So put a little fuel down ther and check. I simply assumed synthetic despite having flown planks in the glorious good smelling days of castor we'd always "wet" an engine to check bearing. Irony is that I'm currently flying the same motor in the Experience with non synthetic. Yumpin yemminy I love that smell!

Steve

[Skytrek]

Long day, so no work on the project. Thanks so much to both of you and I will taking a look tomorrow. We shale see!

[Mak_abank]

I have always liked the O.S. engines because they are VERY easy to tune and are very reliable. Ive always liked them. When i used to race, i had a phantom engine and it was EASILY able to hit 70MPH, but i must say that it is nearly impossible to control it at that speed.