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HomeRC & PowerAircraftHelicopterEngines Plugs Mufflers Fuel › Os 50 Hyper what would be the cause
04-24-2009 07:21 PM  9 years agoPost 21
datidun

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N Ireland

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vincey said something that cocerns me there about the ring ,if i remember right it was a bit tricky getting in on ,but if it was not on right surely something would have happened in the first couple of flights ,since the new bearing its been over 15 flights,how often should the piston ring be replaced ,or should it be relaced with the rear bearing ,regarding the top bearing its hard to see if its gone ,i dont think those ones come out.

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04-24-2009 07:41 PM  9 years agoPost 22
dkshema

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Cedar Rapids, IA

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if i remember right it was a bit tricky getting in on
If it was "tricky" getting the ring in place, you did it wrong. Installing a ring is easier than getting Congress to spend four trillion dollars these days.

http://www.mecoa.com/faq/rings/install/install.htm

Front bearings come out as easily as rear ones do when you heat the crankcase. They usually fall out when properly heated.

Your piston looks as if it ran lean before you peeled off the upper part of the piston's crown, as evidenced by those nasty score marks all up and down the piston skirt. I'll vote that you were lean, the piston crown failed, followed by the end of the ring getting snagged in an exhaust port opening. That broke the end of the ring off, it flailed around inside the combustion chamber a few times before exiting, stage right, into your muffler. Clean out your muffler real well before putting it back on any engine.

Does Rapicon have castor oil in it? What's left of your piston looks mighty varnished up.

Rings only need to be replaced as they wear out, leaving an end-gap that's too large for a good seal, and don't have enough tension to seal the cylinder. That takes a lot of tanks of fuel. Of course, if they break, you're in the market for a new motor. Check out the cost of a head, piston, and ring, and determine if it's better to replace or repair.

When you DO replace a worn ring, you should run a brake cylinder hone through the cylinder to remove the glaze from the walls and restore the cross-hatch pattern. Break in as if it were new.

-----
Dave

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

Team Heliproz

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04-24-2009 07:50 PM  9 years agoPost 23
VooDooX

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San Francisco Bay Area CA, US (San Mateo)

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Your piston looks as if it ran lean before you peeled off the upper part of the piston's crown, as evidenced by those nasty score marks all up and down the piston skirt. I'll vote that you were lean, the piston crown failed, followed by the end of the ring getting snagged in an exhaust port opening. That broke the end of the ring off, it flailed around inside the combustion chamber a few times before exiting, stage right, into your muffler. Clean out your muffler real well before putting it back on any engine.
+1

i said the same thing but i like your storytelling better
looks like a piece of the ring broke off and bounced around like a ping pong ball inside cratering everything it hit then eventually finding its way out the exhaust i wouldn't be surprised if it was in the pipe you should shake the pipe and see if you hear anything inside

Velocity 50 "99.9999999999999% of an atom is empty space." also 01001000 01001001

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04-24-2009 07:55 PM  9 years agoPost 24
datidun

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N Ireland

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thanx for the reply ,im confused about being to lean ,the backplate was cool to touch ,rapicon fuel has synthetic oil in it 22 percent oil,i have only started using it ,i will try for another engine ,this time keeping the idle needle at factory setting ,there are no sighns of overheating on the inside of the head which usually would be grey colour would it not.

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04-24-2009 08:06 PM  9 years agoPost 25
LonR

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Macomb,Mi

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Same thing happend to mine a few weeks ago .Im running the Hyper with a Revolution tune pipe and the pipe has 2 holes,one on top for a left mount and one on the bottom for a right mount.Well the stupit plug on the bottom came off and she ran lean.Motor cut off and had to auto land.When I checked the compression there was none .Pulled the motor apart and she looked just like yours and the pitting is from the pice of ring thats missing .So like dkshema said,that for sure looks like a lean run .

600LE,OS55,OS PowerBoost pipe,Align 610's,Spartan

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04-24-2009 08:26 PM  9 years agoPost 26
datidun

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N Ireland

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ok so what should a piston look like if its ran lean ,black or dark brown i thought like a grey colour

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04-24-2009 09:27 PM  9 years agoPost 27
LonR

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Macomb,Mi

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The piston will look like it started to melt/deformed on the edge and feel ruff.It will also have a blackish brown color like you said.Thats where it gets hot and cooks the fuel to the piston.A nice tunned motor will have a tan color on the piston and most pistons still look new on top even after 5-6 gallons as long as its running a tad bit rich,the wet fuel keeps the piston clean.Im on 3hrs of sleep so I hope you understand what im saying lol.

600LE,OS55,OS PowerBoost pipe,Align 610's,Spartan

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04-24-2009 10:05 PM  9 years agoPost 28
bopshi

rrApprentice

greenport ny

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varnished ring groove?
Is there any caster in that fuel? Might be that varnish built up and carbon behind ring causing wedging effect . Have seen piston failure due to this on 2 stroke outboards. Just my 2 cents. D. MANN

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04-25-2009 01:12 AM  9 years agoPost 29
Yug

rrMaster

UK. Herts

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A big lump of something got in there.
This would normally be a bit of bearing but you say your bearings are good so it's either one of 5 things........
1 foreign matter sucked in
2 some swarf in the engine
3 piston ring gave up
4 crap sucked in through the exhaust fannymould
5 other casing or piston particles that decided to depart

Vegetable rights and Peace

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04-25-2009 02:09 AM  9 years agoPost 30
dkshema

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Cedar Rapids, IA

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What kind of fuel were you running prior to switching to the 22% synthetic oil Rapicon?

Perhaps all that nasty brown stuff on the skirt is from the previous fuel, as suggested -- burnt castor oil residue. That much goo on the piston skirt, if castor oil residue, will cause the motor to run hot, lean, and just plain make it difficult to find a decent needle setting.

I'd also think that for 20% fuel, 1-1/4 turns open on the main might be on the lean side.

-----
Dave

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

Team Heliproz

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04-25-2009 02:20 AM  9 years agoPost 31
steve 01

rrProfessor

Grand Rapids MI

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send it back to os that failure shouldnt happen, They replaced one for me that had the same failure at 3 tanks

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04-25-2009 02:32 AM  9 years agoPost 32
Carey

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Allentown USA

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Voting that the ring was not put on correctly. Ask me how I know.

If the piston key isn't lined up with the gap in the piston ring, you will crack the piston ring (over the key) and all bets are off from there @ 17,000+ rpm.

Every time you replace a piston, replace the piston retaining rings or another motor will look like the one in the OP.

Sorry my man. These things can be a rough mistress.

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04-25-2009 04:35 AM  9 years agoPost 33
Quandumphone

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Yuma, AZ

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How old is this motor?

If someone asked me to guess, I'd say that motor is several years old and in very bad shape. I'm not talking about the damage, just the tarnished and smeared appearance. The reason I say this is because I think the motor isn't really that old at all. This motor was run lean and very hot multiple times. Additionally, it looks like bad fuel was used to include using castor oil. I don't understand why they still use that in model airplane fuel. Trying to tune an engine in this condition is really difficult. It's really no wonder that it came apart.

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04-25-2009 10:44 AM  9 years agoPost 34
datidun

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N Ireland

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ok first of all the motor is over a year old ,second it has never run on fuel with caster oil in it ,it used to run on pro synth 20 percent which has 18 percent synthetic oil ,1 full turn and a quatrer on the main needle is not lean ,could keep my finger on the backplate all day ,if there was something wrong with the piston ring alignment it would have broke in the first flight or so ,this heli had over 15 flights,i did not find the bashed up pieces of the ring ,i will have to flush out the exhaust.

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04-25-2009 11:36 AM  9 years agoPost 35
datidun

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N Ireland

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i flushed out the muscle pipe and found the piece of piston ring that did the damage aswell as small pieces of the front of the piston

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04-25-2009 01:16 PM  9 years agoPost 36
Carey

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Allentown USA

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if there was something wrong with the piston ring alignment it would have broke in the first flight or so ,this heli had over 15 flights,
Believe it or not, the motor can continue to run (albeit crappy) with a damaged piston.

I just broke in a new YS91. Did my usual break in method, friends around me the whole time watching my every move. The thing just wouldn't tune for anything. Three folks standing around that run YS91's just couldn't get it to run correctly, while the other ones were singing sweet.

Sick of messing with it, I took it out for a full inspection. A good part of the piston (1/4 of the circumference), the ring land (?) had broken off. The ring was intact but there was obvious blow by where the ring land was missing.

Bastards!!

Finding weaknesses in RC heli products is my gift.

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04-25-2009 04:00 PM  9 years agoPost 37
airdodger

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Johnston USA

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That engine was run lean most of the time, Does not matter where the needle was set. There could be restrictions or damage to the needle seat, or just machined different. I don't care if the backplate was making ice. The piston seized and on the down travel the aluminum caused the ring to stick and hence broke the ring and ring land off. There should be no discoloration on the parts using synthetic fuel. If you see brown that is you burning the oil meaning too hot period.

Chris

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04-25-2009 04:34 PM  9 years agoPost 38
rexxigpilot

rrProfessor

Florida

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^ exactly correct!

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04-26-2009 12:58 AM  9 years agoPost 39
malb34

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Northern Ireland

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If it seized how did it keep running to bash the broken piece around the head to make those marks and then out the exhaust?

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04-26-2009 01:22 AM  9 years agoPost 40
datidun

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N Ireland

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regarding the needle seat are you talking about the main needle ,how does one check that

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