Bearing prices, for shame

[jim ivey]

Guys
Lets think about this. The 4 strokes usually turn less RPM's.So do the 
bearings. The 4 strokes raw fuel is introduced into the head and onto the 
top of the piston. Most of this concoction  leaves the head through the 
exhaust except that, that gets blown by the ring.This is then, the way the 
bearings get oiled.This oil stays on the bearings in a more 
concentrated(undiluted) form.
A 2 stroke has the raw fuel swirled around the bearings all the time(not 
good for oiling).This oil is highly diluted by nitro and methanol and has to 
have a negative effect on the oiling of the bearings.Add this to the fact 
that the 2 strokes make their power at higher RPM's and you have a case for 
premature bearing failure.
My way of looking at this.

Jim Ivey



jivey61 at msn.com





>From: Bob Kane <getterflash at yahoo.com>
>Reply-To: discussion at nsrca.org
>To: discussion at nsrca.org
>Subject: Re: Bearing prices, for shame
>Date: Tue, 14 Oct 2003 18:54:17 -0700 (PDT)
>
>One thing YS's DON'T suffer from is bearing life. I ran a two-stroke Irvine 
>.72 in my Ultimate KAOS, flying a couple of times a week + the local 
>contests. Always ran it dry, used after-run oil and never ran it lean. I 
>had to change bearings 4 times in two seasons.  One of the first signs of 
>bearing wear was a need to bump up the idle trim to maintain idle speed. 
>The bearings always showed signs of corrosion (not red rust, but dark 
>stains on the races) and the inner race was very loose compared to a new 
>bearing.  My YS and Saito motors, run under nearly identical conditions, 
>never showed signs of bearing corrosion or wear the way the two stroke 
>bearings do, without running them dry or using after run oil .  At first I 
>thought it was due to the fact that four strokes don't draw raw fuel into 
>the crankcase (true for Saito and OS), but YS motors do push raw fuel 
>through the crankcase. I am currently at a loss to explain the difference. 
>Maybe temperature? The cooler running two-strokes
>  allow raw alcohol to sit in the crankcase perhaps? Maybe YS has a magic 
>bearing supplier?
>
>
>
>
>Troy Newman <troy_newman at msn.com> wrote:
>The Bearings in my YS's all run long time...I know I have one motor that 
>has 2 years on the bearing and I would say 800+ Flights.
>
>I run a good quality fuel and use an air filter....especially when flying 
>on a grass runway....
>
>They last forever seems like....I have only changed a bearing in a YS as 
>prevention, since I was already re-building it. Bearings were fine just did 
>them because even $20 for a bearing is cheap.
>
>I rarely even hear of guys having their YS's with bearing problems....the 2 
>strokes seem to have the Bearing problems. I guess its good they are easier 
>to work on than the 4 strokes.
>
>
>TN
>
>
>
>Bob Kane
>getterflash at yahoo.com
>
>---------------------------------
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