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HelicopterEngines Plugs Mufflers Fuel › OS 55 Carbon or burned piston?
12-09-2016 05:17 PM  11 months agoPost 1
dasd

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Carol Stream, IL

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I pulled a 55 hyper out of the heli for maintenance (bearings etc.). When I pulled the head off, I discovered this. So, the question is what caused the mess? Too rich, too lean, bad fuel, etc. My other 55 is clean as a whistle. What do you think.

Formerly SunFunFlyer.

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12-09-2016 06:14 PM  11 months agoPost 2
MikeSherman

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Franksville, WI

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Do you run castor oil?

How does the ring look? Any shiny spots?

-Mike

Team QuickUK Pilot
Team Heliproz

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12-09-2016 06:44 PM  11 months agoPost 3
dasd

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Carol Stream, IL

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No castor. The ring was fair, but I'm replacing it anyway. Liner looks good. Same fuel used in another identical engine without this issue. I'm puzzled because I have never seen it before.

Formerly SunFunFlyer.

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12-10-2016 02:10 AM  11 months agoPost 4
crflyer

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Maine

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Were all the head bolts tight?
Almost looks like the head was leaking air.

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12-10-2016 05:19 PM  11 months agoPost 5
dasd

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Carol Stream, IL

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All the head bolts were tight. I thought of that, too. I'm doing a rebuild and I'll look for air leaks, but it's really weird.

Formerly SunFunFlyer.

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12-10-2016 09:21 PM  11 months agoPost 6
crflyer

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Maine

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I would replace the head gasket during the rebuild,and make sure there are no air leaks. The engine appears to have been run lean.

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12-11-2016 12:58 AM  11 months agoPost 7
JuanRodriguez

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The Villages,​Florida

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Doesn't look like a lean run to me ..... to the contrary, those sort of deposits indicate a rich running motor with carbon deposits as a result.

Been there, done that and old enough to know better.....

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12-11-2016 04:27 AM  11 months agoPost 8
Gearhead

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Vt

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was the ring stuck when you took it apart ?? if so I'm betting it was stuck a while

Jim
Buzz Buzz Buzz

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12-11-2016 02:14 PM  11 months agoPost 9
slickporsche

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American/Philippines

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os 55 carbon

I would agree with gearhead as to a stuck ring. You can see the evidence in the blow-by, and the resulting carbon and varnish build up. What does the other side of the piston look like? The cylinder must have a hard glaze on it also. I hope I'm wrong there, as it would make it difficult for the new ring to seat.

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12-11-2016 03:08 PM  11 months agoPost 10
wjvail

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Meridian,​Mississippi

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How was he engine running before you decided to take it apart? How does the crank look? Bearings look OK? Was it eating plugs - because it looks like it should have been.

The jury is still out on what the problem is but something is clearly not right. I've never seen a burn pattern like that. I wouldn't rule out there being several problems. It's not out the the question that bad fuel, run lean, caused the ring to stick.....

"Well, Nothing bad can happen now."

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12-11-2016 06:01 PM  11 months agoPost 11
ICUR1-2

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Ottawa, Ontario

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Carbon
clean it up, especially where the ring sits
While you're at it change the bearings
on the 2nd or 3rd rebuild change the connecting rod if your burning rings

spending time, paying attention

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12-11-2016 06:41 PM  11 months agoPost 12
dasd

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Carol Stream, IL

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The bearings were ready for replacement. The ring was stuck and snapped on removal. I'm going to replace the head shim, bearings, piston, and ring. The other side of the piston looked pretty good. I showed you the exhaust side. The engine was not eating plugs. In fact, the plug I pulled out was in good shape. The liner looks really clean, too. I guess I'll see what happens after the rebuild.

Formerly SunFunFlyer.

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12-12-2016 03:30 AM  11 months agoPost 13
Gearhead

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Vt

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edited

I showed you the exhaust side
it's funny how the top of the piston has the Carbon on the "exhaust" side, that's usually from a lean run or an air leak, yet the Carbon on the side of the piston is on the "front" of the piston,, no mater the Ring was stuck, but I don't think it was stuck too-too long or there would be more Carbon,
I'm wondering if you had a lean run and that is when the ring stuck, and then you got the Carbon on the front side of the piston, then of course you ran the engine more

Jim
Buzz Buzz Buzz

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12-12-2016 03:00 PM  11 months agoPost 14
wjvail

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Meridian,​Mississippi

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Out of curiosity, what does the underside of the head look like? Any scorching or pitting? Does the muffler port show any signs of distress?

You have really created a mystery with those pictures. As I said before, I've never seen piston in quite that condition. Maybe if it was run for a very long time on castor fuel but never with synthetic...

"Well, Nothing bad can happen now."

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12-12-2016 05:51 PM  11 months agoPost 15
dasd

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Carol Stream, IL

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To answer wjvail; the underside didn't look super bad, but it wasn't clean by any means. The muffler port had the 'burn' marks, too. I took an xacto knife and scraped it off the exhaust port of the crankcase. It's almost like the fuel was contaminated. The weird part is the glow plug. It is in really good condition.

Formerly SunFunFlyer.

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12-13-2016 06:32 AM  11 months agoPost 16
dkshema

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Cedar Rapids, IA

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Seems to be a lot of room in the ring groove. In your pics, the ring looks to be stuck to the lower part of the groove, closest to the wrist pin. I don't recall the ring having that much vertical play in its groove.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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12-13-2016 11:10 AM  11 months agoPost 17
Four Stroker

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Atlanta

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Hey Dave;

Perhaps you could explain to the boys how an engine comes to be burned up ?

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12-13-2016 12:31 PM  11 months agoPost 18
ICUR1-2

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Ottawa, Ontario

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Seems to be a lot of room in the ring groove. In your pics, the ring looks to be stuck to the lower part of the groove, closest to the wrist pin. I don't recall the ring having that much vertical play in its groove.
That's because it is missing in the picture

spending time, paying attention

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12-13-2016 01:06 PM  11 months agoPost 19
dkshema

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Cedar Rapids, IA

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This (above) is an OS55-HZ Hyper piston.
The skirt is nice and smooth, the ring-gap is just a bit larger than the ring itself.

In the OP's second picture, it certainly looks as if the ring is still there, stuck in place, with nearly enough room above it for a second ring to be installed.

-----
Dave

* Making the World Better -- One Helicopter at a time! *

Team Heliproz

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12-13-2016 01:35 PM  11 months agoPost 20
wjvail

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Meridian,​Mississippi

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Dave... I wonder if you are looking at the picture correctly.?.?

In the OP's picture I see a place for the ring and an oil grove. Here is a pic from my OS .55HZ-R

Bill

"Well, Nothing bad can happen now."

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HelicopterEngines Plugs Mufflers Fuel › OS 55 Carbon or burned piston?
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