I had to replace the bearings in my O.S. 50 hyper, so what better time to do it than after a failed inverted auto atempt?
The first thing I had to deal with was the piston sleeve, which was not going to come out without a fight! After stripping everything off of the crankcase, I heated up the oven and baked it for about 7 or 8 minutes. Once I took it out of the oven (looking quite fetching in a mis-matched pair of oven mitts) the piston sleeve came out real easy followed by the everything else and then the bearings with a little pursuasion. The front bearing seemed to be okay, but the rear bearing was very close to exploding! Looks like I got to it just in time.

I ordered the replacement bearings from Boca Bearings and they shipped them out super fast! After looking over the instructions that came with them, it became apparent that I was going to have to remove one of the shields on the side of the bearing. They suggest you carefully make a hole on the outermost part of the shield and then use something to pry it off. I took my time to make a small hole using an exacto blade, and then using a small socket head driver I worked at the shield until eventually it popped off. Unfortunately the bearing now had that "notchy" feeling .
Anyway, after talking to the good folks over at Boca it looks like I must have inadvertantly damaged the race on the inside while trying to pop off the shield. There doesn't seem to be any visible damage, but its really the only explanation. In fact Boca said that they do it themselves occasionally and that its not to be totally unexpected. I'll be sending the bearing back to Boca, who in turn will check it out to see what happened and send another one back to me.

In the meantime I have a second set of bearings, but I am a little apprehensive about attempting to take the shield off again. I'll let you know how it goes......

My old 50SX is starting to make that bearing noise.
They will be replaced tonight with new bearings from www.RC-Bearings.com.
The quality and service is equal to Boca but the price is about half.

Heat is the magic ingredient for bearing replacement.

I have already forgot and left the seals in place on the front bearing with no ill effect.
The rear bearing that comes from RC-Bearings does not have any seals installed.

What is your benchmark or indicators for bearing replacment ?

For me it was when I started to hear an unusually loud noise at idle. Initially I thought I may have worn out the clutch lining and that the metallic sound I was hearing was the shoes catching the aluminum clutch bell, but after another flight or two I noticed a definate drop in power. Being as there is nothing moving other than the engine and clutch at idle I decided I had better drop it out of the airframe and check it out. The clutch lining was just fine and sure enough when I checked out the bearings I found the problem.

I may be up for a bearing replacement too.... recently the bird just didnt feel like it has the pop like it used to @ punch out.... I also was wondering about a sort of "ringing" sound coming out at idle. Sound s like a bell kind of ringing in the clutch bell.

That's it exactly....sounds like you should check them out also.

Once you hear it and identify it you will notice it from a mile away.

After you change one it will become a no brainer to do.

The longest part of the replacement is waiting for the loctite to set so that you can fly more. I keep spare bearings in my field box and can change them at the field in about 1/2 hour.

thanks will order some today.

It seems like setting for long periods of time will cause the need for bearing replacement just as much as actual flight time. I have replaced several sets on engines with one a few gallons through them because they sat for three or four months and when I finally got out to fly, they had that tell-tale rattle at idle.

The biggest culprit is rust causing pitting of the races.
How to prevent rust in the engine is a huge monster debate since everyone's situation is different and what works great for one could be the worst possible solution for someone else.

I am not sure exactly why, but heli engines in helies seem to be more prone to bearing rust than the same heli engine, running the same fuel, by the same person, mounted on a plank.

Here's a few tips I've gathered over the years to identify a bad rear engine bearing.

First, like mentioned already.... a funny noise at idle. Second, blowing glow-plugs often (small bearing debris will punch the glow-plug element it). Third, play in the crankshaft – with the motor out of the heli you should not be able to move the fan side-to-side at all.

I’ve found plastic caged bearings to work best, when they do go bad they won’t throw the cage or put metal through the motor. Eventually they just develop slop and the motor will start to run rough. It's a good idea to replace your bearings yearly, regardless of their condition... nice to start off the season with a fresh one.


Colin

great info.... Who makes those plastic caged bearings.

You can get em' at boca bearing for any application. OS also makes them for their 60-90 size motors (I've been using these and they work great). I don't believe OS uses plastic caged bearings in their 30s-50s though.


Colin

OS uses the metal cage hand grenades in the 50.
When that cage lets go it will take the piston, cylinder, ring and head with it, once in a while a con rod to.
I have had better results with the bearings from www.RC-Bearings.com than from the Boca bearings.
The RC-Bearings are also half the price of the Boca, A win win in my book.
I just ordered some more today for my stock. the rear bearing that just went out in my 50 was the last of the Boca bearings that I had. that 50 only had about 4 or 5 gallons thru it. I have been getting bout 5 cases on the RC-Bearings.

This is just my experience, there are so many variables involved here that your results are likely to be very different.

It is time... Must replace... I have about 10-12 gals through it... I will keep you posted.