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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Advice needed on scratched liner in Hyper 50
02-09-2008 03:03 AM  10 years agoPost 1
john2

rrNovice

Lucedale, Ms.

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Need some advice please. I evidently ran my Hyper 50 too lean even though I could hold my finger on the backplate for 10 seconds or so. The engine lost a lot of power in flight and when I landed the backplate was hotter than it had been being. Testing after it cooled down seemed to indicate I had lost most of the compression. Also this engine only has a little over two gallons thru it.

After tearing the engine down everthing looked decent. The only thing I could see or feel with the tip of a exacto knife was a very small scratch vertically where the ring ends ride against the cylinder walls. My question is this, does the liner need to be replace? How about honing with 600 grit or higher wet/dry sandpaper? Does the scratch have to be completely removed or should I replace the liner?

I have a new ring ordered and will probably reassemble and try it unless a lot of folks say not to.

Thanks,
John

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02-09-2008 03:12 AM  10 years agoPost 2
george0079

rrElite Veteran

USA

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If the scratch is as small as you say, you should be fine...

Hell... I can fix that.
Uh oh..
Nope.
It's ***ked!!!
RE-KIT!!!!!

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02-09-2008 03:15 AM  10 years agoPost 3
TMoore

rrMaster

Cookeville, TN

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Actually, some 320 submerged in a sink full of water followed up with 400 and some oil will work nicely. If you want to wrap the sandpaper around a deepwell socket and work it back and forth in a circular in and out pattern this will restore the cross hatching that the original honing process gave it when the cylinder was originally manufactured.

TM

Delayed Response Operator Not Engaged
AMA SECTION 336 = Good
Drones = EVIL

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02-09-2008 10:00 AM  10 years agoPost 4
john2

rrNovice

Lucedale, Ms.

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Thanks guys!

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02-09-2008 02:17 PM  10 years agoPost 5
Ruff

rrVeteran

Queen Creek, AZ

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Go to an auto parts store and get a brake cylinder hone. Run it through a few times and the scratch will be gone....

Ruff

http://srcha.com

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02-09-2008 02:39 PM  10 years agoPost 6
KevinB

rrKey Veteran

Earth

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I agree with Ruff. Make sure you move the hone up and down the cylinder as it spins and spin it fairly slowly. If you look real closely at the liner wall after, it should have really fine 'scratches' in a cross-hatched pattern. This will show you have removed the glaze caused by the hot run, and the micro-scratches are what retain the oil and thereby help the seal with the piston ring ( aka: better compression ) Just don't set the stone pressure too high on the hone ( if you have one that's adjustable) or do it for too long....or you'll have a Hyper.51 !

Put in the new piston ring after you hone it......it'll be just like new. Which also means, you'll have to break it in again.

Kevin

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02-10-2008 12:58 PM  10 years agoPost 7
Jeff polisena

rrElite Veteran

westpalmbeachflorida usa

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My opinion is to buy a new ring and sleeve if you cant tell if cylinder is egged out you might not get much time out of repair.
I have sanded to clean scratches and some last long time and some I got 1 flight and back to square 1

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02-10-2008 03:58 PM  10 years agoPost 8
TMoore

rrMaster

Cookeville, TN

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The OS cylinder is coated with a substance like Nikasil. I can guarantee that the only way the only way you can get the cylinder out of round is to hone it that way or grind on one side. Sanding with 320 will take forever by hand.

Removing a scratch, depending on the depth is trivial with a little wetordry and water/oil.

TM

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AMA SECTION 336 = Good
Drones = EVIL

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