[NSRCA-discussion] OS 120 AX

[J N Hiller]

The stock bearings in both my 120-AX’es failed prematurely, maybe two cases
of fuel. The first one had serious corrosion, even on the shaft under the
rear bearing as if it wasn’t properly lubed during assembly. The other one
just got loose, (excessive prop rock) so I quit running it. I got
replacement bearings from the local bearing store and left the seals on and
it still feels fine after maybe 6 gallons.
I have never experienced this kind of premature failure before and I have
been running OS motors for about 30 years. Are they trying to build too
large of a displacement in too small of case?
Jim Hiller

-----Original Message-----
From: nsrca-discussion-bounces at lists.nsrca.org
[mailto:nsrca-discussion-bounces at lists.nsrca.org]On Behalf Of John Pavlick
Sent: Monday, September 03, 2007 8:40 PM
To: NSRCA Mailing List
Subject: Re: [NSRCA-discussion] OS 120 AX

Bob,
 How much time is on it? We've had a few around here that ate the rear
bearing in 50 - 100 flights. One of them ended up ruining the sleeve too
(bearing debris). The solution is to replace the rear bearing with an OS
140Rx F.I. (sealed) bearing before it gets bad enough to cause other damage.
The front bearing is a double sealed type already so you won't need to
change that one. This is a really good running motor when you get the
bearing thing straightened out.

John Pavlick
http://www.idseng.com
----- Original Message -----
From: Bob Richards <mailto:bob at toprudder.com>
To: NSRCA Mailing List <mailto:nsrca-discussion at lists.nsrca.org>
Sent: Monday, September 03, 2007 8:35 AM
Subject: [NSRCA-discussion] OS 120 AX

I acquired a plane with an OS 120AX installed, and seem to be having some
issues with it. It came with an APC 16x8 prop and stock muffler. Is not
running as well as I think it should, but I did figure out I had some bad
fuel. I plan to go out again today and tinker with it some more.

What fuel, prop, and what rpm figures should I be seeing?

Thanks in advance.

Bob R.

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