OK, a little stumped. I have limited bearing experience. how exactly do I know when they are bad? I have the back bearing out. It's a little discolored and it feels like it has just a touch of grit in it when you turn it, but even that is exxagerating it I guess it doesn't feel silky smooth. Real uniform though, it doesn't catch on anything. it just isn't as smooth turning as the front bearing. is it bad? I've serachd around this forum for some ideas, but it's all pretty limited to catastrophic failures.

If you took it out it's probably bad now. You should replace it anyway as it's out.

Originally Posted by datsunguy

If you took it out it's probably bad now. You should replace it anyway as it's out.

Huh? how does taking a bearing out destroy it?

Taking bearings out can damage them and it can also not damage them.
If they come out/press out easily they are most likely ok.
If they are forced out there can be side loading damage that can distort the cage.

One good check is to see if there is any crank movement other than rotational. If you hold the prop you shouldn't feel any up and down movement.

Originally Posted by Wookster

Huh? how does taking a bearing out destroy it?

Hammer an punch can damage them. Give it a good washing an see if you can still feel it if yes then replace it. What color is it, silvery blue then it may have over heated for some reason. When in doubt get new.

Originally Posted by Old coot

Hammer an punch can damage them. Give it a good washing an see if you can still feel it if yes then replace it. What color is it, silvery blue then it may have over heated for some reason. When in doubt get new.

Kind of a brownish look to it in a few spots. not a lot, a few rust spots here in there. oh BTW this is the rear bearing that looks iffy. I heated the engine in the oven to 200 degrees and tapped the case and the bearings dropped right out.

If it is rust, it would be best to replace them. Maybe the front one too but that`s upto you.
Heating the case is the best way to do it, they can more or less fall right out.

PS. rust pits will just get worse over time.

If you have them out why not replace them with better bearings? Or just use what you have and then take it apart again later. What engine is it??

Not sure what engine he has either but new set may only be about $25 -/+. Boca bearings can be found on ebay plus others or
http://www.rc-bearings.com/catalog/i...hp?cPath=65_66
Choice is your`s do it now or do it later $$. I`d do it now an save the possible head-ache later.

If you have removed the bearings, then you need to replace them. It is easy to get side loads when you remove them, which damages the races and the cages.

How do you know to replace them?
When you can hear them when the engine is running, a mild howl or whine emanates from the bearings.
If the crankshaft has more forward and back play than it used to have.
When you rotate the crank and they feel slightly gritty or rough.
When you notice some rust spots or rust on them. There is micro-pitting which you can't easily see that damages the races and or balls. Sort of like microscopic potholes. But as the bearings roll over the potholes they get bigger just like potholes do on roads and highways.

I would definitely replace them. No sense having the used ones out and not putting in new.
I would feel like I just wasted my time taking it apart. I find most bearings to be quite
cheap. I like Purvis Industries.

I wd-40'd the bearing just to clean it up a bit. Still seems rough so I guess she's getting new bearings. It's an evolution 45. The trainer motor. The stock bearings are backordered and Bocas with shipping are a bit pricey. Are these things a standard size and tolerance I could pick up from a store like any bolt or screw?

Try rc-bearings.com With Boca you got the part numbers you can use that with rc-bearings to locate and price them.
http://www.rc-bearings.com/catalog/i...hp?cPath=21_22

Ditto for putting the engine in the oven to help remove/install bearings.

I have had to change the wheel bearings on my Subaru a few times and putting the knuckle in the oven makes it easier to press them out.

For installing the new ones the knuckle goes back into the oven and the bearing goes in the freezer. After a while the bearing simply slides into the knuckle.

This will work with our RC engines also. Sometimes a few thousandths is all you need.

Originally Posted by earlwb

Try rc-bearings.com With Boca you got the part numbers you can use that with rc-bearings to locate and price them.
http://www.rc-bearings.com/catalog/i...hp?cPath=21_22

Ahh thank you!!! bearings are ordered. Hopefully I have them by the end of the week. The stock bearings were backordered on the horizon site. These things are a lot cheaper. the stainless are less than the stock bearings.