Another bearing question....

[Ed Miller]

I second what Dean mentions, most 2 strokes cannot tolerate "loose" parts,
especially in the piston/rod/wristpin and rear bearing area. A loose wrist
pin to piston fit or sloppy upper con rod will constantly change the timing
of the exhaust and intake ports besides affecting compression seal. What
also happens is a shock load is applied through the rod to the crank pin and
into the rear bearing causing small flat spots or dents in the race and
balls. If you hear your 2 stroke pinging, especially the larger displacement
ones, add head shims to improve consistency and extend rear bearing life. I
suspect a lot of the OS 140 bearing issues, besides corrosion are related to
the hammering of the rear bearing from pinging/detonation. We stress our
engines pretty hard, if you go over the edge it shouldn't be a surprise when
problems occur.
Ed M.
----- Original Message -----
From: "Dean Pappas" <d.pappas at kodeos.com>
To: <discussion at nsrca.org>
Sent: Friday, October 24, 2003 1:32 PM
Subject: RE: Another bearing question....


> Hi Dave,
> To answer your question, yes, maybe. The shakes and wiggles can also
disturb the piston, causing it to wiggle and blow-by.
> That can put high pressure spikes in the crankcase, and will drive the the
pump nuts. The remarkable thing is that worn parts almost anywhere in a
2-stroke make for bad carburetion, or a poor idle. Just look at how a loose
connecting rod messes up the idle. It's uncanny.
> Dean
>
> -----Original Message-----
> From: Dave Smith [mailto:davidsmith at ns.sympatico.ca]
> Sent: Thursday, October 23, 2003 6:56 PM
> To: discussion at nsrca.org
> Subject: Re: Another bearing question....
>
>
> Dean:   If the base compression is inconsistent,losing compression,would
> that not cause the pump to output less pressure,and less fuel to the
carb??
>
> Regards,,,,,,,,,,,,,,,Dave
>
> ----- Original Message -----
> From: "Dean Pappas" <d.pappas at kodeos.com>
> To: <discussion at nsrca.org>
> Sent: Thursday, October 23, 2003 4:39 PM
> Subject: RE: Another bearing question....
>
>
> Hi George,
> It's a double whammy: the extra heat is bad, but the big killer is the
loss
> or inconsistency of the base compression seal as the crankshaft wiggles,
in
> its bore.
> So what engine has the funny symptom you described? Let me guess, a worn
out
> YS 60 ...
>
> Regards,
> Dean
>
> -----Original Message-----
> From: george kennie [mailto:geobet at gis.net]
> Sent: Thursday, October 23, 2003 2:03 PM
> To: discussion at nsrca.org
> Subject: Re: Another bearing question....
>
>
> Boy, that blows me away! Somebody that's an engine guru please explain why
> a
> faulty bearing causes the mid-range loading-up problem.
> I have a 60 size engine that is a few years old that will turn a 12x7 prop
> over
> 12K rpm and idles below 2000, and transitions beautifully, but if I run it
> up to
> full power and let it run for about 30 seconds, at which time it sounds
> awesome,
> and then reduce the throttle to 9000 rpm, it will run good for about 5
> seconds
> and then start to load up and will quit, while at this setting after about
> 15
> seconds.
> It just happens to be sitting on my benchtop with a prop on it and I just
> went
> in and turned it over. The bearing feels smooth, there is no slop in the
> prop
> tips and there is absolutely no end play.
> Maybe I should keep the bearing and order the rest of the parts to build
up
> a
> new engine.
> Hmmmm, .........still confused.
> Georgie
>
> Wayne Galligan wrote:
>
> > My OS will do the loading up in the midrange and die thing.  It has
> happened
> > on the last two bearings thus giving me the warning.  Then of course I
> could
> > verify the end play at the tips of the prop. Funny thing was I couldn't
> feel
> > any roughness.  But after a fresh bearing it ran fine.
> >
> > Wayne
> >
> > ----- Original Message -----
> > From: "White, Chris" <chris at ssd.fsi.com>
> > To: <discussion at nsrca.org>
> > Sent: Wednesday, October 22, 2003 2:55 PM
> > Subject: RE: Another bearing question....
> >
> > > Thanks Wayne.... The first 2 I would expect, the 3rd is new to me, and
> the
> > > fourth....well that kind of says why we care....:)
> > > Chris
> > >
> > > -----Original Message-----
> > > From: Wayne Galligan [mailto:wgalligan at goodsonacura.com]
> > > Sent: Wednesday, October 22, 2003 2:47 PM
> > > To: discussion at nsrca.org
> > > Subject: Re: Another bearing question....
> > >
> > >
> > > If you rock the spinner back and forth and it is not smooth or you
feel
> > > roughness.....bad bearing.   If you grab the prop by the tips and
wiggle
> > it
> > > back and forth and there is end play.... bad bearing.  If you
experience
> > > sudden changes in the midrange like loading up and engine quits on
spool
> > up
> > > and plug is OK....possible bad bearing.
> > >
> > > Or if you see metal filings coming out the exhaust....... TOO LATE bad
> > > bearing and engine.
> > >
> > > Wayne G.
> > > ----- Original Message -----
> > > From: "White, Chris" <chris at ssd.fsi.com>
> > > To: <discussion at nsrca.org>
> > > Sent: Wednesday, October 22, 2003 2:32 PM
> > > Subject: Another bearing question....
> > >
> > >
> > > > Hi!
> > > > I hear of guys getting anywhere from 35 to 400 flights on bearings:
> > > >
> > > > What are the first signs of bearing problems. Since starting
> > Intermediate
> > > > practice in July, I have just got into flying the same
airplane/engine
> > > > regularly enough to wear on an engine and tell the difference in
> > > > performance.  I have 97 flights on a Zen/Webra 145AAR combination. I
> use
> > > > Cool Power 15% and after run oil religiously.  I have a  tach which
> > varies
> > > > so much with light emissions that I deem it as unreliable.  So what
do
> > you
> > > > look for?
> > > >
> > > >
> > > > Thanks, Chris
> > > >
> > > > -----Original Message-----
> > > > From: gene.maurice at comcast.net [mailto:gene.maurice at comcast.net]
> > > > Sent: Wednesday, October 22, 2003 2:07 PM
> > > > To: discussion at nsrca.org
> > > > Subject: RE: bearing question
> > > >
> > > >
> > > > Try WWW.AFCBEARING.COM. Great prices and so far a good product. They
> > carry
> > > > all of the standard sizes, but some of them have to be shipped from
> > Japan.
> > > I
> > > > am using their sealed SS bearing in my OS 160 with the seals and
> grease
> > > > intact. 120 flights (+-) without a problem. And I am using crank
> > pressure
> > > to
> > > > power a Perry pump. This is after going through 2 sets of carbon
steel
> > > > bearings after less than 35 flights each.
> > > >
> > > > --
> > > > Gene Maurice
> > > > AMA 3408 NSRCA 877
> > > > Plano, TX
> > > > gene.maurice at comcast.net
> > > >
> > > > =====================================
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