efish

My Feedback: (5)

Hi everyone, I volenteered to help a fellow flier change the bearings on an old OS 61RF. Everything came out pretty normally, except that I can't seem to get the rear bearing out from the crankcase. That is, its not seated anymore, but I just can't get it to fall out of the crankcase.

I've tried most of the usual methods - heat etc, but there just does not appear to be enough clearance for the bearing to come out. Took some measurements with my calipers and it seems that there is about a .5mm difference.

Is this some pecularity unique to this particular engine?

On the otherhand, the engine is old with an unknown and uncertain history. Could it be likely that the rear of the crankcase is distorted thus impeding the passage of the bearing?

Would be grateful for any help or suggestions. Thanks!

DarZeelon

EFish,


The rear bearing in this engine is a 6903 (17x30x30 mm).

It is not possible the rear of the crankcase is distorted so far as not clearing the 30 mm O/d of the bearing...
It is only supposed to be held in the seat!

rainedave

My Feedback: (1)

Put the case in your oven and heat it at 325° F (around 160C) for ten minutes. Then, hit the rear of the case against a block of wood. It will drop out. If it doesn't, repeat the process at 350&deg' F.

When you install the new bearing, slide it onto the crankshaft and put it in your freezer. Meanwhile, heat the case again as above. The crank and bearing will slide right in place. You might need to tap the back of the crank with a block of wood to fully seat it.

David

Bax

My Feedback: (11)

With some of the SF/RF-series of engines, the outside diameter of the bearing is very close to that of the hole in the rear of the case. You need the case warmed and the bearing exactly-square to slide it out. If the bearing is slightly-crooked, it won't come out.

anuthabubba

My Feedback: (102)

efish,

Recently I had the same problem with an SF engine. Seems that while the bearing was loose in the crank case it wouldn't 'fall' out. I had to reheat the case at 250F for 10-15 minutes and carefully align the bearing outer race with the rear of the case before it came out.

Good luck,

Terry in LP

blw

My Feedback: (3)

Or, tighten down a prop with the drive washer installed to see it everything will snug up in place.

efish

My Feedback: (5)

Thanks guys.

Darzeelon - thks, good to know, since the cost of a nerw crankcase would likely make this engine beyond salvage.

I had already tried the heat-and-smack method with no joy.

Bax & Terry, thanks - will try again, this time paying more attention to the alignment of the bearing. Part of the problem is that the rear bearing is in pretty bad shape and even after some anti-freeze cleaning, its still pretty grotty.

Rainedave, thanks, the freeze-and heat is my standard bearing installation process though I've found I can often omit the freezing part on many engines!

Flyboy Dave

My Feedback: (21)

....grind an old screwdriver like this so you can reach in from the front and get
on the bearing. Heat the case to 350 for 10 minutes, then come in and bump the
bearing out. The bearing may be corroded or has been bound-up in the case.

Use some solvent too, to loosen it up from corrosion.

FBD.