Bad "luck" with rear crankshaft bearings.

Boomer · 04-12-2004, 08:47 PM

Today I had to replace another YS 80 rear bearing that was in my Fury. I need some help in figuring out what I'm doing wrong. Over the years I have had to replace way too many rear crankshaft bearings, more than anyone I know of. I run all the fuel out at the end of the day and try to drain any residual oil out of the muffler via gravity. I live in the Arizona desert - H2O is not the issue. I keep my helis indoors where the temp and humidity is controlled. I think it is acid from spent nitro that is not removable in any means a normal person would pursue at the end of the day. I know that the longer an engine sits after it has been run has a definate effect on how quickly the rear bearing goes south. Yes, it's undeniably rust and nothing else. Yes, I know methanol is hygroscopic. I still refuse to believe it's a moisture issue. Having said that, we all know rust has everything to do with iron and H2O, but one thing for sure, the front bearing never rusts, yet runs in the same fuel. Gravity drains that bearing dry. Unfortunately the opposite is true of the rear bearing in that all the nasty stuff ends up surrounding it there.

It doesn't matter what brand name bearing I use, but I do notice some brands of fuel (one in particular) shorten bearing life more than others. The MP2 is an obvious source of residual goo that I'm willing to deal with simply due to it's superior performance (just my opinion).

I joined this forum because there are lots of guys with serious flight time here. You just can't put a "price" on that (if you know what I mean). I'm hoping you vets can shed some light on this.

Thanks for the replies, Scott.

Beast · 04-12-2004, 08:52 PM

Try the boca ceramic they are pricey but they should last longer.

TMoore · 04-12-2004, 09:20 PM

Boomer,

Try the OS bearings.

Terry

Doug · 04-13-2004, 07:48 AM

Dissemble your bearing and look at the outer race (see if you can identify the orientation (sometimes there is a "witness" stain at the top due to the counter bore or the cylinder.)) If a "washboard" affect is seen in the "upper" half then it's "false Breneling" You can try to change your head speed slightly as you may be in a "resonant" point.

04-12-2004, 08:47 PM	#1
Boomer Registered Users Join Date: Apr 2004 Location: Az.	Bad "luck" with rear crankshaft bearings. Today I had to replace another YS 80 rear bearing that was in my Fury. I need some help in figuring out what I'm doing wrong. Over the years I have had to replace way too many rear crankshaft bearings, more than anyone I know of. I run all the fuel out at the end of the day and try to drain any residual oil out of the muffler via gravity. I live in the Arizona desert - H2O is not the issue. I keep my helis indoors where the temp and humidity is controlled. I think it is acid from spent nitro that is not removable in any means a normal person would pursue at the end of the day. I know that the longer an engine sits after it has been run has a definate effect on how quickly the rear bearing goes south. Yes, it's undeniably rust and nothing else. Yes, I know methanol is hygroscopic. I still refuse to believe it's a moisture issue. Having said that, we all know rust has everything to do with iron and H2O, but one thing for sure, the front bearing never rusts, yet runs in the same fuel. Gravity drains that bearing dry. Unfortunately the opposite is true of the rear bearing in that all the nasty stuff ends up surrounding it there. It doesn't matter what brand name bearing I use, but I do notice some brands of fuel (one in particular) shorten bearing life more than others. The MP2 is an obvious source of residual goo that I'm willing to deal with simply due to it's superior performance (just my opinion). I joined this forum because there are lots of guys with serious flight time here. You just can't put a "price" on that (if you know what I mean). I'm hoping you vets can shed some light on this. Thanks for the replies, Scott.

04-12-2004, 08:52 PM	#2
Beast Registered Users Join Date: Apr 2004 Location: Laurel MD	Try the boca ceramic they are pricey but they should last longer. __________________ . Beresford

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04-12-2004, 09:20 PM	#3
TMoore Registered Users Join Date: Apr 2004 Location: Cookeville, TN	Boomer, Try the OS bearings. Terry

04-13-2004, 07:48 AM	#4
Doug Registered Users Join Date: Apr 2004 Location: Naples Fl	Dissemble your bearing and look at the outer race (see if you can identify the orientation (sometimes there is a "witness" stain at the top due to the counter bore or the cylinder.)) If a "washboard" affect is seen in the "upper" half then it's "false Breneling" You can try to change your head speed slightly as you may be in a "resonant" point.