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YS FZ 140 S Piston Damage.

Old 02-12-2014, 09:10 PM
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Default YS FZ 140 S Piston Damage.

I have a YS FZ 140 S that I was flying, and suddenly I heard a, Shall we say "Abnormal sound" then the engine immediately stopped. After a safe landing, and getting the plane home and upon dis-assembly I found that the exhaust valve had snapped off of the valve stem, causing catastrophic Cylinder head damage. upon further examination of the engine, the only other damage was to the top of the Piston. there was no damage to the cylinder wall, it is still completely smooth! I have another complete head assy, so my question is will I have any problems running this engine with the Piston damage that it received? there is no obvious high spots, or rough spots or catches at all. all the pits seem to be pretty shallow, probably less than 1/64th of an inch (guessing depth, but very shallow none the less)..

Check out the pics and let me know what you think! remember, the pictures look much worse than they look and feel, in person!



Thank you in advance for any input on this situation!

Craig..
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Old 02-14-2014, 07:40 AM
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sent you an email....RON
Old 02-14-2014, 11:31 AM
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Hello, Ron..

I didn't receive an E-Mail from you, even checked to see if it had been sent to my spam folder! I also double checked that I had the right E-mail address in my settings, everything looks good.

Craig.

Last edited by SeaJay; 02-14-2014 at 11:36 AM.
Old 02-14-2014, 12:33 PM
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i sent an email from my i phone. i would replace the piston.....but most pistons and sleeves go together so its costly. if over 50.00 i would try it like it is. their is a limit to what i would spend on it but you have to decide for yourself. generally speaking marks on the top don't hurt much. you dropped a valve in the motor alright that happens but shouldn't if everything is ok. is the engine worth the money or not........that is the question. i can't see it hurting anything else. go easy with it and see what happens like it is, is my take.........good luck.........RON
Old 02-14-2014, 01:13 PM
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Geeter,

I have found a parts supplier, and the piston can be purchased seperately from the cylinder for about $80.

Decisions, Decisions!!!

Craig.
Old 02-14-2014, 01:25 PM
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yes a piston from central hobbies is 78.00 and a ring is 24.00. checked it out. i would run it the way it is if it were me. that's just me talking but i would see what happens. i would be different if the piston had a hole in it or something. smooth the top of the piston out ,but don't touch the top around the sides. a small stone wheel on a dremal should do it............let us know how you make out......ok.?
Old 02-14-2014, 10:12 PM
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Geeter,

Yes, I have decided to just run the engine with the piston, will smooth out the top as much as possible. But I am also going to get a Bowman ring, since it's only about $17 shipped. seems that everyone who has used one of his rings swear by them, so since the engine is apart, I will go ahead and have one sent to me, put it in and re assemble and just run it!

I will keep you updated as to the progress and performance of the engine!

Craig.
Old 02-15-2014, 09:00 AM
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Yes that's a good idea. They are the best rings available. Your making a very smart move by doing that. I 'm sure it will work out for you. Again good luck & keep us updated......geeter.
Old 02-15-2014, 11:28 AM
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Do you have any input about "Lapping" the valves? I was thinking that since I have the head off, and the head is already a used head, that it might benefit from a Valve job! I was thinking that I could use some polishing compound and lightly lap the valves just to make sure they are seating and sealing well..

What are your thoughts on this?

Thanks, Craig.
Old 02-15-2014, 12:28 PM
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yes i have done that on an os four stroke. you can use toothpaste as a lapping compound. just a little. be careful taking the snap rings off the valve stems. they are prone to get lost easy. take the valve out and clean the head and valve with solvent. put some compound on the backside and back into the head. use a piece of rubber tubing or small fuel line over the stem and use the tubing to turn the valve back forth between your fingers.[ never] use a dremel or drill do it. it don't take much. then clean it and see if it's shiney on the seat and valve. if not do more. do them both being very careful with the snap rings. remember the springs have pressure against them. clean and reassemble with a drop of oil on each valve stem . you should have it. re`ajust the valves to around .004 "............geeter
Old 02-15-2014, 12:37 PM
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puting a ring on the piston. to keep from breaking it. start the ring by putting it on top of the piston,angle it into the groove and gently run it around the top and down into the grove alittle at a time. never spread it apart and try to slide it down over the piston at one time. you will surely break it. ask me how i know............just something i thought of to help.........geeter
Old 02-15-2014, 09:55 PM
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Geeter,

Yes, those little Retainer clips are easy to loose.. I took the beat up head apart, and lost one of the clips from that, but I at least have 3 extras for the head I am actually using..

I am glad that you told me about not using a drill, as that is what I was considering using..

Also the reminder about the ring installation technique is always appreciated, I would hate to have to come back here and explain that I had just broke a new ring on install!

Craig.

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