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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › YS91 SR bearing replacement due, any advice?
03-30-2009 04:33 PM  9 years agoPost 1
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Hey fellas,

I am going to replacing the bearings in my SR soon. I have never done a 90 motor before. All of my experience changing bearings has been on 50 Hypers. I have read some of the posts on here regarding special care when uninstalling the carb/regulator. Is there anything else that I should know before tackling this project? Anything specific to YS motors that I should know that isn't the same as the smaller OS motors?

Thanks for any tips!

Gaui Greatness X7, X5, NX4, X3

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03-30-2009 06:45 PM  9 years agoPost 2
Dr.Ben

rrMaster

Richmond, VA, USA

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Nah, except that you may want to have a spare gasket set on hand in case you tear one of the ones in the carb/reg stack.

Everything pretty much unscrews and goes back on in the reverse order of how you took it off.

The sleeve fit is often tighter than OS uses. You may need a little heat from a heat gun to pull the sleeve out.

Ben Minor

Peak Aircraft/Team Minicopter Team Futaba Team Kontronik USA

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03-30-2009 10:15 PM  9 years agoPost 3
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Okay, thank you!

I have it disassembled. I managed to save the gaskets with a brand new exacto knife.

Gaui Greatness X7, X5, NX4, X3

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03-30-2009 10:23 PM  9 years agoPost 4
S76 Mech

rrElite Veteran

Hatboro, Pa.

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got it fully disassembled, thanks

Gaui Greatness X7, X5, NX4, X3

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03-31-2009 01:47 AM  9 years agoPost 5
S76 Mech

rrElite Veteran

Hatboro, Pa.

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Okay, YS Gurus, let me know what you think about this ...
1. looks like I need a connecting rod, the brass bushing has alot of play and is clunking around. I noticed this 'after' I put the entire motor back together and installed 'fully' into the 700. So, I took it all apart again, ripped the motor apart, and found the con-rod sloppy on the crank shaft.

2. when I had it together, I found the clunking by spinning the start shaft by hand. While doing this, I also noticed that there isn't a whole lot of compression. I could turn the start shaft adapter by hand. Never noticed this before, and quite frankly, it ran good before the disassembly. Lots of power. Are these YS motors known for having alot of compression, or is not out of the ordinary to be able to spin the start shaft by hand?

Note: the only thing not installed was the muffler which has nothing to do with compression.

Gaui Greatness X7, X5, NX4, X3

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03-31-2009 01:57 AM  9 years agoPost 6
airdodger

rrElite Veteran

Johnston USA

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The engine needs to be spun over fast to get enough pressure behind the ring to seal it to the wall, can't tell compression by hand. If the engine was fine before you took it apart it should be fine now, but depending on the time on the engine changing a rod is not out of the question. There is no way we can tell the clearance from behind the computer so judgement is up to you. A little clearance in the rod end gives a place for more oil. The good plyon engines click because of the large clearance but run fine.

Chris

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03-31-2009 02:08 AM  9 years agoPost 7
S76 Mech

rrElite Veteran

Hatboro, Pa.

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airdodger, thats kinda what I was hoping to hear. Before I removed the motor to change the bearings, the motor was running great! Really, it had a ton of power and I really never had to mess with the settings, fuel and fly.

Once it started making the slightest bit of bearing noise, I took the motor out of the heli for bearing replacement. I have ruined enough engines by running them past that first tell tail sign of rear bearing noise.

Other than the rusty bearings (which weren't that bad at all), the con-rod was sloppy.

I think I'm just going to replace the con-rod and see if that takes up the slop. If it does, I will rebuild the rest of the motor and install, and test fly. If she's good to go, then I'm in luck!

Gaui Greatness X7, X5, NX4, X3

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