OS FS-40 bearing replacement, how?

OS FS-40 bearing replacement, how?

Post by Frank Loeff » Thu, 28 Nov 1996 04:00:00



Hi,

My old and trusty FS-40's main bearings are apparently damaged, as I
wiggle the prop, the whole crankshaft will slightly move "sideways".

I plan to replace both the front and the rear bearing. I removed the
crankcase cover, and boy is the inside of my engine corroded. I'll
have to take the after-run maintenance more seriously going forward.

Anyway, could someone please briefly outline the procedure to
replace the bearings, in particular:

1) Before I remove the camshaft, what's the best way to establish
and later reproduce its correct position with respect to the gears
on the crankshaft?

2) Once I have removed rod and piston and camshaft, how should
I remove the crankshaft? I figured I'd put the engine in an oven
for a while, then tap the crankshaft out with a wooden hammer.

3) Will the rear bearing stick to the crankshaft? Will the front
bearing stick in the crankcase?

4) What's the correct procedure to install the new bearings?

I'd very much appreciate all advice!

--
Frank Loeffel :-)

 
 
 

OS FS-40 bearing replacement, how?

Post by David Turnbu » Mon, 02 Dec 1996 04:00:00



Quote:

>Hi,

>My old and trusty FS-40's main bearings are apparently damaged, as I
>wiggle the prop, the whole crankshaft will slightly move "sideways".

After you have things apart, make sure it's actually the bearings and
the crankshaft didn't wear.  If the bearing seize it's possible that
the crankshaft will turn in the bearing and wear down.  It doesn't
happen often, but it's important to note while you are calculating
parts costs for a rebuild.

Quote:
>I plan to replace both the front and the rear bearing. I removed the
>crankcase cover, and boy is the inside of my engine corroded. I'll
>have to take the after-run maintenance more seriously going forward.

>Anyway, could someone please briefly outline the procedure to
>replace the bearings, in particular:

>1) Before I remove the camshaft, what's the best way to establish
>and later reproduce its correct position with respect to the gears
>on the crankshaft?

OS engines have a timing mark.  I believe it points at the pushrods
when the crank is at TDC.

Quote:
>2) Once I have removed rod and piston and camshaft, how should
>I remove the crankshaft? I figured I'd put the engine in an oven
>for a while, then tap the crankshaft out with a wooden hammer.

The oven probably won't help at this point.  Just pound it out
carefully.

Quote:
>3) Will the rear bearing stick to the crankshaft? Will the front
>bearing stick in the crankcase?

Here is where heating the engine will help.  If you are lucky, 250
degrees and a sharp rap on a short stack of newspapers or magazine
will get it out.  But since your's is corroded you will need to pound
it out.

DONT USE A BLOWTORCH like some of the books describe.  It's too easy
to***up your crankcase if you don't know what you are doing.
However, if you are a master metallurgist this is by far the fastest
way.

Quote:
>4) What's the correct procedure to install the new bearings?

A safe way is to put the front bearing in the crankcase first.  Then
put the rear bearing on the crank.  Then join the two.

Quote:
>I'd very much appreciate all advice!

Get some Z-best engine cleaner.  It may help removal of that rear
bearing.  It will for certain help installing the new ones if you use
it to remove all the crud while the bearings are out.

David  AMA# 543851  FCC# N9OMH

Tri Village RC'ers
http://www.FoundCollection.com/