When is it time to overhaul a motor

[thefrog]

My OS 91 HZ-R has had close to 50l of fuel through it. I'm busy with some maintenance on the heli and am wondering if I should be changing the ring and rear bearing on this motor. How often is it typically done? Power seems good and compression is still good.

[breezer1]

Usually right after a lean run, or, neglecting to run it dry after flying and using no after run oil then letting it sit for a month.
Check your bearings and see if they are smooth. If it has good compression, I'd leave the ring, sleeve, and pistion alone.
Some flyers will tell you that, "Since ;it is apart, change everything". A personal decision and depends on if you have the spare parts in hand at the time. A well seated ring/sleeve is a power maker vs a new one that needs breaking in again.

My 2 cents.

Breezer1

[dchekas]

Originally Posted by breezer1

Usually right after a lean run, or, neglecting to run it dry after flying and using no after run oil then letting it sit for a month.

I never run my engine out after flying, and I never use after run oil. I've let engines sit for months, and they always fire right up and look awesome on the inside. Neither are musts, IMO.

I change my piston ring right around 16-20 gallons, and usually change the rear bearing while I'm at it.

[thefrog]

I haven't had a chance to pull the motor yet. I have a ring and rear bearing but I'll check the motor's condition before deciding on whether to change anything.

[frypan]

I am coming up on 9 gallons and the engines just keep getting more power!

[thefrog]

I opened the motor - there's very little wear on the piston and the ring is still ok. The rear bearing isn't as smooth as it could be though. I've changed the ring and rear bearing as I had the parts at hand.

I guess I should run it a little bit rich for a few tanks to bed in the ring and bearing?

[dchekas]

I usually richen it 2-3 clicks over my normal needle setting, and don't beat on it hard for the first few flights. I gradually increase the loading on it until I hit a gallon or so, tHen it's back to normal.

[wifeorheli?]

Fly it till it blows up then replace as needed! Ive noticed i run cool power 30 and after a week it starts breaking down in the motor. I used to run them dry by clamping the fuel line but i have been pulling the line now and running it dry. Then pull plug and backplate and after run oil it. If you make sure you dont run it super hot they will last a while! I noticed my governor was reving recently it was due to a bad rear bearing which i couldnt believe. Some motors like my novarossi have less compression when dry and not running but when everything heats up its very hard to turn motor over.

[Jafa]

An even better way to run the engine dry is to drain the fuel tank,
hook everything back up and open the fuel clamp
Start the engine and run it dry
Doing it this way the carb sees the exhaust pressure and operates a little better,
hence running dry and clearing out fuel in the crankcase a little better

CoolPower oil has anti-corrosion additives and should not hurt the engine (but the methanol will)

[Raptor30_V1]

Hello,

There are people doing some preventive maintenance on their engines every 10 gallons of fuel, most people don't ..

An other approach is to monitor the condition of your engine by:

- compression it has: won't work for most people because they don't know how to do that ..
- observe carefully differences in the sound of your engine: not that easy neither for many novices ..
- engine gets hotter: is a good sign and easy to spot with a temp-monitor: unfortunatelly most of the time it's already to late ..

So what can you really do ? IMO the most important things you can do, are:

1.) if having some main bearing with a metal cage, replace it after 5 gallons by a quality bearing with plastic cage (e.g rc-bearings or bocca)

2.) After every flight session, empty completely your fuel tank and having the radio and model switched on, start the engine (igniter) until all residual fuel is run through the engine. Be sure all exhaust gases leaved the engine/ muffler

3.) Even though modern fuels have a good inhinition against rust, if you don't use your model for months, remove the plug, fill some drops of after-run-oil and using the starter, make the oil settle in the engine. Put the plug on. The only negative point here is, if the after-run-oil doesn't harm the rubber/ seals inside carb.

4.) Try to listen your engine's sound and watch the temperature. Don't be to afraid, having some bearing with a plastic cage, the harm is way less..

5.) If in doubt, remove the engine from your bird and take quick look at main bearing and piston/ ring/ sleeve. If flying in dusty enviroment, take the chance to clean your carb.

Many people spend lots of money having new gadgets or ever new canopies on their birds, but a very good investment is, to change the fuel lines (incl. the ones in the tank) at least every year. This prevents the engine from running lean. You can turn your carb's needle as much as you like, as long as there is some leckage in one of the fuel lines, you won't have a chance to setup your engine and pretty sure will run pretty lean.

Best Regards,
Oliver

[RC-Bearings]

The fuel makers that talk the most about not needing after-run oils are the ones that I have seen rust the most bearings. A stainless steel bearing will eliminate most of that problem. Also, I would not use a bearing with a steel retainer in a heli motor.