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HelicopterEngines Plugs Mufflers Fuel › Why is my piston so clean ?
03-30-2005 11:35 AM  13 years agoPost 1
Cicolli

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Perth, Western Australia

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A couple of days ago I was out flying my heli and the the OS 50 SXH started to make a bit of a rumbling noise. I pulled the engine apart and it was obvious that the rear bearing had failed, destroying the engine.
The thing that I find interesting is the total lack of carbon build up on the piston. It is totally clean having the same finish as the exterior of the engine. I have had quite a few engines and the piston tops are usually a nice golden brown when I pull them apart. Does anyone have any Idea why the piston would be so clean and could there be a relationship between the rear bearing failure and the lack of anything on the top of the piston.
Thanks in advance,

Paul.

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03-30-2005 11:56 AM  13 years agoPost 2
Dave E

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Carbon burns off with heat. The piston must have been hot, no different than your fireplace. Possibly too lean?

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03-30-2005 11:59 AM  13 years agoPost 3
Darksider

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Derby United Kingdom

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if the top of your piston looks clean and new it means you've been running your engine settings just right, leave them as they are and replace the faulty rear bearing, and while your cranks out, perform the crank mod

see here: http://runryder.com/helicopter/t136872p1/

Gareth

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03-30-2005 12:05 PM  13 years agoPost 4
Cicolli

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Perth, Western Australia

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Hi Dave E,
I was thinking that may be the case but the engine was quite cool after flight. (you could touch the back plate indefinately).

Darksider,
I have decided to bin the engine and have ordered a hyper. For the price of a new liner, ring, piston, bearings and conrod I may as well get a new one.

Paul.

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03-30-2005 12:48 PM  13 years agoPost 5
Doug

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Port Saint Luice Florida....

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With the mixture "just right" the piston will have a "stain" which will wipe off easly. Sounds like you are right on the money.

First member of Member of Bearings Anonymous

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03-30-2005 02:03 PM  13 years agoPost 6
Darksider

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Derby United Kingdom

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a light tea staining is not abnormal no, mine tend to have this but i have found thats because i tend to run mine a little on the rich side, but a piston thats shiny and new looking does not necessarilly mean the engine's been run lean, if it's been run lean it tends to take on a slightly different brown staining which is much more difficult to remove than the tea stain, it's entirely possible that you just hit the exact right spot on your settings that kept the piston looking new and not causing pre-detonation from running lean, my tnx engine looks like this inside as clean and new as the day i bought it, and that engine's been going for ages, allthough i've found it's alot more difficult to perfect that setting in the same way with the helicopter engines.

Gareth

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03-30-2005 06:11 PM  13 years agoPost 7
ChiefG

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Hawaii

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Here's what mine looks like going thru 8 gallons, there's a light brown stain that you can rub off with your finger, other than that no problem so far (bearings still in good shape). Did the web mod and watch the temp everytime I fly.

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03-30-2005 10:18 PM  13 years agoPost 8
3d type

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Bridgeport,CT USA

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you must also be running full sinthetic oil content fuel, castor would have the inside of the motor brown in no time.

how'd the ground come up like that ?

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03-30-2005 11:10 PM  13 years agoPost 9
Cicolli

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Perth, Western Australia

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Seems as though the bearing failure and the piston colour are unrelated then. Thanks for the pictrue ChiefG. At least I have my needle settings about right.
I have always used syntheitc oil (coolpower) in my engines and until this engine have never had a problem. In fact this is the first engine that I have damaged internally. I hope that the hyper does not have the rear bearing problems that this one does.

Paul.

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03-31-2005 01:19 PM  13 years agoPost 10
Raptor_in_Swede

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Stockholm /Sweden

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Hi Paul
It is bad that an engine that has been runned in so good circumstances as yours got a bearing failure.
I would call it a manufacturing quality problem and a possibilty for warranty claim.
How old is the engine and how much fuel is used in the engine ?

Raptor 30V1/TT39H/Hatori#415/GY401_9253
Hirobo GPH GT/TT50H/Hatori #544/GY401_9254
RD8000

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03-31-2005 01:32 PM  13 years agoPost 11
Cicolli

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Perth, Western Australia

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Hi Raptor in Swede,

The engine is a couple of years old but has not done alot of work. Probably has had about 20 - 30 gallons of fuel through it. I use 20% low vis coolpower and 20 percent nitro. I just hope that my new Hyper will not suffer from the same rear bearing problems that the 50 SXH's have. Thanks for your reply,

Paul.

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