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Backup Generator Compression Issue


thiggy's Avatar
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05-04-11, 12:30 PM   #1  
Backup Generator Compression Issue

When the power went out due to Wed's storms, I went over to my Mom and hooked up her generator to keep her freezer & refrigerator going. I went back later to re-fuel it. After gassing it up, I was unable to start the thing. It had no compression!! It had been running fine prior to shutting it off to re-fuel. The generator is a 5000 watt battery start with a Robin OHV single cylinder engine. It is about 5 or 6 years old, probably has no more than 10 hours run time, and I crank it up every month or so to keep it opereational. The engine turns over freely by hand (or with the starter) and it makes no pecular internal sounds which would hint at mechanical damage or brake-down. Does anyone have any suggestion what to look at before I begin a major engine tear-down? There is no manual compression release, and I am not aware of an automatic release.

 
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05-04-11, 12:37 PM   #2  
Hi. The only thing I could think of is it may have a low oil cut off. Have you checked or changed the oil? There it a wire that comes from a senser low by the oil drain plug that detects low oil. I have seen the wire come off on some, because its only a plug type clip.

The small engine repair guys will be chimeing in and will help you further if thats not the problem

Let us know.

Mike NJ

 
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05-04-11, 05:45 PM   #3  
I'm fairly certain you have a stuck valve. When you shut down a hot engine with older fuel in the tank, it's common enough for it to stop in a position where a valve is open. As it sits with the valve open, it sticks, and you have to pop the valve cover and get it loose. You may want to pick up a can of carburetor cleaner and spray the valve stem a bit to cut the varnish so that it doesn't stick again. It would probably pay to keep the fuel treated with marvel mystery oil. Today's fuel just doesn't last long and contributes to a whole lot of new problems, including this.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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05-04-11, 08:03 PM   #4  
Thanks for the suggestion Cheese. I will remove the valve cover and see what I can tell about the valve action. You mention treating the gas with Marvel Mystery Oil. Is this used rather than Stabil? How many oz to how much gas? Thanks, Thiggy

 
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05-04-11, 10:37 PM   #5  
In addition to stabil preferably. I don't recall the mix ratio but it's on the can.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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05-10-11, 07:16 PM   #6  
Just a follow-up for you Cheese. I checked out my Mom's generator this evening. When I pulled off the valve cover it became apparent that the intake valve was stuck in the open position. I was surprised how easy it was to remove the rocker arms. No tool was needed. After removing the valve retainers and spring, I was able to free up the valve and get it back in running condition. What would cause the valve to seize up like that? The oil was clean with no deposits visible in the head or valve cover. I am concerned about a reoccurance in the future. I thought that Subaru Robin was supposed to be a high quality engine.

 
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05-10-11, 11:24 PM   #7  
It has nothing to do with the quality of the engine. It's the quality of the fuel. I'm betting it was running fuel more than a few months old.


"Who is John Galt?" - Ayn Rand (Atlas Shrugged)

God bless!

 
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05-14-11, 08:50 PM   #8  
I had one of those engines in my last generator...a powermate 5000, it's a great engine.

There is a compression release, the fact you felt no compression obviously was from the stuck valve, but there is one and it aids in starting.

Speaking to one of the Robin reps, he said to fill the oil from spill to spill...don't go by the dipstick, and use high quality synthetic. I used Amsoil 4-stroke for small engines and it never missed a beat.

Keep in mind, these things run hard at 3600 RPM's, don't skimp on the oil. Run a few hours on some full synthetic and change it each hour for 2 changes and see what happens....could be some slight sludge built up but not likely. I ran some BG44K through mine and I think it helped in cleaning up the valves.

Those engines are definately a snap to tear down.

 
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