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OS 50SX making a strange noise

Old 09-02-2003, 04:22 PM
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Jeff396
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Default OS 50SX making a strange noise

Hi,

I bought an OS 50 SX at the beginning of this season. It has and still runs and starts great. Problem is that at my last two visits to the field it has started making a strange noise. At 1/3 throttle it sounds just like an air cooled Volkswagen Beetle engine and the sound intensifies as the throttle is advanced. I'd almost call it a whirring sort of buzzing sound. We've checked that everything is tight on the plane and even tried to run it without the cowl. I also checked that the prop was balanced. This engine has run so well that it still had the original glow plug in it. I also took off the back plate thinking that a bad rod might make this sound but everything looks good. Does anyone have any idea what might be causing this problem? I'm running Byron fuel with 10% nitro and 20% oil content.

Jeff
Old 09-02-2003, 04:42 PM
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ChuckAuger
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Default OS 50SX making a strange noise

Dollars to doughnuts it's the bearings. They make a whirring sound when they're going out.
Old 09-02-2003, 04:47 PM
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Default OS 50SX making a strange noise

Jeff, you're not the only one.

Mine is making the same noise. I've only had the engine since last fall.

Its performance didn't suffer when it made this noise, it just sounded so strange, that I landed right away.

I think I will replace my bearings, and see what that does.
Old 09-02-2003, 05:48 PM
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Jeff396
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Default OS 50SX making a strange noise

I took mine apart with the exception of the crank and bearings. The crank sure seemed to rotate smoothly and there was not one bit of slop or grinding that I could feel or hear. I suppose that could be that the trouble only just started though. As with yours I really didn't notice any fall off of performance. I think I'm gonna swap it out with my .46FX whose place it took for the time being. Let me know when you get those replaced if that solves your problem.

Jeff
Old 09-02-2003, 06:10 PM
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Jeff396
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Default OS 50SX making a strange noise

I just went down and tried something on my three current engines..... .91FX, 46FX and the 50SX. I just rotated the prop quickly back and forth without going through compression. The .50SX is easily four times louder than the other two so I guess a new set of bearings is in my future too.

Bill Baxter, the OS engine rep, said that not using after run oil or lots of aerobatic maneuvers could cause premature bearing failure. Okay, so I'll start using after run oil again. I didn't figure I needed to unless I wasn't flying for an extended period of time. As it is I have been flying once or twice each weekend. But as far as the aerobatic flying goes....???????

Jeff
Old 09-02-2003, 06:36 PM
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GuamJan
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Default OS 50SX making a strange noise

Mine sounds like a freight train going by. Since it's still under warrenty, I will send it back for repair.
Jeff, thks for starting this thread, I didn't have a clue.
Old 09-02-2003, 07:06 PM
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DMyer
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Default OS 50SX making a strange noise

Most likely the rear bearing.... shouldn't wear out that fast... even if not using after run oil like you should. Seeing several of you with the same complaint it may be an institutional problem with O.S.... maybe they did find a way to cut $10 off the price. If it was my engine I would put a quailty rear bearing into it(phenolic/plastic retainer cage) instead of a cheap metal caged one like the one that probably came with it.
Old 09-02-2003, 10:31 PM
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Jeff396
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Default OS 50SX making a strange noise

Any suggestions on a source and brand of better bearing? The only name that comes to mind is Boca bearings.

Jeff
Old 09-02-2003, 11:23 PM
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Azcat59
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Default OS 50SX making a strange noise

Put Boca bearings in it and I will bet your noises will go away. And as for aerobatic maneuvers damaging the bearings, that is setting off my BS detector...... The worst thing that damages bearings is running the engine too lean. Then failing to run the engine dry after flying and after oiling is next.

Clair Sieverling
Old 09-08-2003, 07:36 PM
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Jeff396
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Default RE: OS 50SX making a strange noise

Here's an update....

I ordered a set of Boca High speed bearings with the composite bearing cage for $34.90 shipped last Wednesday. I got them Friday and did the swap. I was a little concerned as the old bearings seemed fine. I installed the new ones and thought there was an improvement with just a little noise when the prop was moved quickly back and forth. I took it to the field today and after one noise free flight you couldn't hear anything when the prop was moved quickly back and forth.

Anyways, thanks for the help and good luck to those who still are having problems.

Jeff

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