Another question. I bought a used OS .61 FS about 3 years ago. Just got around to starting it for the first time last weekend. I used Wildcat 15% nitro and 18% oil. It started up right off and ran great for about 2 minutes- just enough time to get the needle adjusted. Then it quit. At that point it had little compression. I took the engine apart to inspect the various components. The push rods looked good and functioned when I turned the engine- opening and closing the valves. THe head looked good also-no cracks or gasket leaks that I could see. The liner looked good as well-no scars or scrapes-the fit is still tight. The only thing I could not get out is the piston. This is a ringed engine and I was thinking that maybe I broke or compressed the ring-although if it broke it wasn't evident in the liner. How do you get the piston out of this engine? I tapped the liner out abot 2/3 of the way from the bottom-as far as I could reach. DO I continue to pull it out from the top to take enough pressure off of the piston to disconnect it from the crank? If this was a real car or truck engine I'd be more at home! Thanks, Tracy.

There was most likely nothing wrong with the engine except you had the throttle closed.

Also on a old unused engine, a valve will stick open and or a pushrod will jump out of position holding a valve open

To get the piston out, you have to heat up the case a little and push the cylinder sleeve up above the wrist pin extraction hole on the rear of the engine. You withdraw the wrist pin and then lift the cylinder sleeve and piston out of the engine.

I do not recommend you do this for everything will be stuck with hardened castor oil and difficult to get out.

To look at the ring will most likely do more harm than good?

To determine is the compression is bad ( worn out ring or sleeve), first you need to prove that the valves are not sticking or leaking. The easiest way to determine this is to turn the engine over by hand while listening to the exhaust and intake port for a hissing sound. If you do not hear a leak there, then put a small amount of oil into the glow plug hole, reinsert the glow plug, turn the engine over to see if the compression has increased. (open the carb all the way by the way. If you have it closed the compression can seem low because not enough air is being sucked in and the compression can seem low). If the compression does increase with a little oil then you might want to tear the engine down but I would try to get it started again as I have had the experience of having thought the compression was bad ( low restistance when cranking by hand and then after running the engine again everything would be ok). If you do have ring trouble and want to resleeve and put in a new ring the the piston will come out by pulling the wirst pin out through the
hole in the back of the clyinder wall after the sleeve is lifted enough. Sometime the pin is stuck because of congealed oil and it helps to heat it first and the try to pull it out by inserting a small wire with a slight tang on it. You have to sort of wedge it sideways and pull. Some pins are harder than others. Don't lose the teflon scuff pads. It helps to not pull the sleeve all the way out. That way the piston is not floating sideways. Hope this helps a little. I ran one of these engines for more than 20 years. I re- sleeved it and ringed it twice.

Sometimes those four strokes will play "compression games" with their owner....I think
they do it on purpose too, just for the heck of it. Sometimes the compression feels
great, and we smile....other times the compression feels weak, and we frown. The
engines get a kick out of playing with our emotions....they know we paid way too much
of our hard earned dollars for them, and will go way out of our way to provide for their
care and feeding.

They watch as we frown at the gas pump....paying three dollars to three fifty for a gallon
of gas....then gladly fork out fifteen bucks or more for a gallon their "special" fuel. They
love being pampered.

As long as the compression isn't leaking to much from the valves or rings, just give it a good
run....and it will probably make you smile again....

FBD.

Quite right, and we love pampering them - 4 cycle fools that we are!

Willits,
I have had similar situations happen with one or more (can't remember which ones or whether it was the same one) of my Saitos. One was a flameout during a flight on my 91, after landing and trying to restart it, it had NO compression! I pulled the valve covers and checked everything I could think of but found nothing. Just for the heck of it, I took my electric starter and spun it over - it started, and the compression was back! I have also had the same thing happen to one of them that had sat unrun for a while, with the same solution - spun it over, everything came back OK. Still don't know what caused it - kind of suspect maybe a sticking cam follower.
Dave

YOu guys were right on! I put the engine back together and there was tons of compression! Don't know how, don't know why, and don't really care-just glad its back. Thanks to all of you who responded, Tracy.