When to replace the bearings
 

Hi Guys,

I have a YS110s which has done quiet a lot of running with no problems
It then started to quit running a couple of times, seemed low on power, all checks were made to see what the problem was and none could be found.

I stripped the engine down, only to find the rear bearing had worn enough to allow the crankshaft ring to wear away at the crancase. This sent fragments of metal up into the piston.... yep the piston liner is deeply scratched. Hence why I had low power.

It did not blow the glow plug.

My questions are:

How do you know when to replace the bearings.

How do you guys store your engines after flying for the day, also for long lay up periods during the winter.

Thanks
Mike.

RE: When to replace the bearings
 

I run my engine dry and that concludes the storage procedure that I use....others perhaps use a different method.

As for the bearings, that depends on how much use or where the engine was stored. My planes and engines are in my workshop in the basement which is dry and always at 70 degrees and never had a bearing rust on me. I know some guys who replace their bearings every year whether they need it or not and others that never replace them until complete failure. I replace mine when they don't feel right or the plane starts to exhibit any strange behavior that I can't explain.

RE: When to replace the bearings
 

Hi Petec,

Interesting to here your reply.

Someone mentioned, if the RPM drops by 1000, check the bearings for wear.

The rear bearings will fail before the front bearing.

Mike

RE: When to replace the bearings
 

I hadn't given them much thought until one of my 1.10's started producing dark exhaust. Seemed to run OK until it stopped one day at a race. When I tore it down, the end of the rod had been wearing on the case. I have since replaced all the bearings in my four 1.10's.

RE: When to replace the bearings
 

Well let's summarize. If you feel that an engine is a perishable unit, then run it until it quits and throw it away. If you expect to extend the service life by rebuilding an engine several times, then do routine maintenance - at least tear it down and inspect once a year. Either philosophy is valid. A rebuilt engine will never be quite as good as new. A rebuild can cost half as much as a new engine.

RE: When to replace the bearings
 

When you state that a rebuilt engine will never be quite as good as a new one,
I disagree, it depends on the level of the rebuild,
you can just gave it a new set of bearings or go the whole hog.
I can rebuild a engine so it is better than a new one, more power and better idle.
But you are right about the cost.

Will

RE: When to replace the bearings
 

Bearings and a ring $50. Quite a bit less than 1/2 price. I guess it depends on how far you want to take it. Mine run fine now. I'm pumping 60% nitro through them. If I can get another racing season for $50 I'm happy.

RE: When to replace the bearings
 

Thanks to all of you who have replyed, some very interesting thoughts.

Mike

RE: When to replace the bearings
 

If you run good fuel, tune it correctly, and keep the motor clean it will have a lot less problems. I raced the same engine on 50+ percent nitro for two years with out any need to replace parts. With that said, if the bearing feels rough or if you have a unexpected hard landing (some call it a crash) then the rear bearing can be damaged and should be replaced.
Skids

RE: When to replace the bearings
 

Hey Skids;

What size engine were you racing ? Old Dave had some stories about running 63's at 18K with stiffer springs and 60%. That's a lot of HP. I've accidentally run 63's at 17K on 30% without blowing them up. In fact they didn't seem to mind.

RE: When to replace the bearings
 

I guess a routine inspection once a year may well be worth while.

Over the weekend, I took a peek inside a YS91FZ which I've run for 3 years without any problems. The rear bearing had signs of corrosion. A stip down of the motor showed no damage to the piston or liner.

New bearings installed and it runs perfectly.

Mike

RE: When to replace the bearings
 

I've run a bunch, but the motor I currently use is the out of production 1.20. On 50% plus nitro I've had my motor turning a 14x13 prop in the mid 10's with no problems.
Skids