YS 140 FZ Sport Valve Issue  
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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> YS Engines Support >> YS 140 FZ Sport Valve Issue
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YS 140 FZ Sport Valve Issue - 6/30/2008 4:41:18 PM   
y2thomas2000


 

Posts: 13
Joined: 1/26/2007
From: Hoover, AL, USA
Status: offline 		I recently purchased a 140 FZ Sport NIB from a fellow flyer. The engine runs fanastic with exception to the fact that I have damaged the exhaust valve twice this week when starting.

The 1st time, it happened when I was starting the motor. The electric starter spun over and after a few revolutions the motor came to a sudden halt. The engine push the valve down into piston and bent it. I ordered and replaced the valve.

The 2nd time, after running and flying most of the day, I spun the starter and heard a metal on metal clank and the engine slammed to an immediate halt. This time the valve, valve spring, and the valve seat (a small aluminum tube located inside the head on the exhaust side) came out and had once again hit the piston.

There is no part # for this aluminum valve seat on the manuals. Has anyone ran into this type of engine malfunction or could there be error in my starteing process. I turn the prop several turns to build tank pressure and prime the motor, then I use an electric starter.

I am getting a little frustrated with this motor as I have never had any trouble out of my other nine 4 stroke engines.
       Post #: 1

RE: YS 140 FZ Sport Valve Issue - 6/30/2008 5:47:39 PM   
petec



Posts: 569
Joined: 1/26/2002
From: Beaver Falls, PA, USA
Status: offline 		That valve seat is part of the head assembly and should not have come out. I wonder if the first impact caused it to come loose.

_____________________________

Team Black Magic
Pattern Junkie..Revver Brother #82..Gear Head

(in reply to y2thomas2000)
       Post #: 2

RE: YS 140 FZ Sport Valve Issue - 6/30/2008 6:08:04 PM   
dmccormick001


 

Posts: 95
Joined: 2/13/2005
From: Soddy Daisy, TN, USA
Status: offline 		Well, for starters, there's no reason you shouldn't be able to start that motor with an electric starter. I've been starting mine with one for quite a while, and the engine doesn't care how it's turned over, as long as your electric starter has enough torque to turn it over, you're OK.

Now, as far as the first problem you had is concerned.......

quote:

The engine push the valve down into piston and bent it. I ordered and replaced the valve.


The engine can't just "push the valve down into the piston". The valve spring holds the valve closed against the valve seat, and the action of the cam rotating against the push rod, which in turn pushes against the rocker arm, which in turn pushes against the end of the valve (valve stem), causes the valve to open momentarily and allow fuel in/exhaust out. So for your valve to strike the piston, the valve spring must have come loose, or broken, or something. You don't mention replacing any other parts or fixing anything else, so if all you did was replace the valve, then you may not have really fixed the problem the first time. What obviously happened is that your exhaust valve came loose, dropped down into the combustion chamber, and was hit by the piston as it came up on the stroke. But you should have checked the all the other parts to try to determine what caused that valve to drop into the combustion chamber in the first place.

quote:

The 2nd time, after running and flying most of the day, I spun the starter and heard a metal on metal clank and the engine slammed to an immediate halt. This time the valve, valve spring, and the valve seat (a small aluminum tube located inside the head on the exhaust side) came out and had once again hit the piston.


This sounds like the same problem just happening again, except for one thing. The valve seat should not, under any circumstances, just fall out of the engine unless the engine has been run at extreme temperatures, and even then it seems unlikely. If you are running it very lean, and running it hard, it might get hot enough to make that happen, but I'd just about have to see that to believe it.

Bottom line is this. You've got problems you shouldn't have on a brand new motor, problems you may not be able to fix yourself after the second time, after the tube in the valve opening fell out. You're lucky these events only happened while you were starting the engine, and not while it was running, or you probably wouldn't have much engine left. I'd send it back to YS with a detailed explaination, and hope they'll treat you right when they repair it.

David

< Message edited by dmccormick001 -- 6/30/2008 6:09:59 PM >

(in reply to y2thomas2000)
       Post #: 3

RE: YS 140 FZ Sport Valve Issue - 6/30/2008 9:38:44 PM   
y2thomas2000


 

Posts: 13
Joined: 1/26/2007
From: Hoover, AL, USA
Status: offline 		Thanks for the feedback Petec and DM,
You were correct, the valve seat is a part machined into the head assembly and failed to stay in place. I spoke with YS and they are going to help me with the issue. Other than this issue, YS is truely in a class of it's own. The craftmanship is impressive.

(in reply to dmccormick001)
       Post #: 4

RE: YS 140 FZ Sport Valve Issue - 7/1/2008 2:44:30 AM   
petec



Posts: 569
Joined: 1/26/2002
From: Beaver Falls, PA, USA
Status: offline 		Funny thing about YS engines; either you love them or you don't. I sold off every other brand engine I owned except my Jetts for my speed planes and only have YS now including my heli. They have been dead reliable for me and hopefully you will have the same luck with them as well.

Pete

_____________________________

Team Black Magic
Pattern Junkie..Revver Brother #82..Gear Head

(in reply to y2thomas2000)
       Post #: 5

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All Forums >> Glow Engines, Gas Engines, Fuel & Mfg Support Forums >> Engine Manufacturers Direct Support Forum >> YS Engines Support >> YS 140 FZ Sport Valve Issue
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