Help!
I really need some help from the experienced Glow Engine guys.

I purchased an alleged new in box OS 120 Surpass E 4 stroke engine (same as currently sold by Tower) from a fellow.
It appears new in box with no fuel residue, no signs of having been mounted, no residue in or on the muffler, etc, etc.

I put a prop on it today and discovered that it has virtually no compression. I would not say the prop freely spins as I do feel a slight amount of resistance in certain spots as I rotate the prop but's it's sure not much.
Just for a reality check I did the same thing on my OS 91 4 stroke and it has far more compression and kick as it rotates.

I pulled the valve cover off and it is spotless as new inside and the valves and the push rods due go up and down and seem secure.

Could this be a valve adjustment problem? Could OS possibly send out a motor in this condition? Not likely so I assume someone like the owner may have tampered with it.

If it might be valve adjustment can someone please direct me to a site or link that clearly illustrates the procedure?

Could it be something else? What should I check?

This is only my 2nd glow engine so I am obviously in need of some help from the experienced guys out there.

Thanks for any help you can provide.

Ken C

Here you go: http://manuals.hobbico.com/osm/fs-120s-e-manual.pdf

The very first thing you should check for is proper valve adjustment.

Prior to making any adjustments, just make sure that the rockers are both loose at TDC. If they are loose, valve lash doesn't enter into the compression issue as both valves are closed.

Put a few drops of fuel into the glow plug hole and then re-install the plug. Open the throttle full open and hand crank it a few times. My guess is that the compression is going to suddenly appear and all is well.

Mount the engine and fire it up. It isn't broken it yet, so it hasn't reach full compresson abaility yet. Chances are very good that there is nothing wrong with the engine. Most complaints about no comression of 4 strokes comes from handcranking them with the throttle shut down. If it can't get air through the carb, there is nothing to compress.

Try the little bit of fuel and open the carb and see what happens.

Don

Is the glow plug installed?

It would be more weird if a NIB ringed engine had compression. Turning freely with little resistance is expected with a new ringed engine.

You're going to need to mount this and break it in according to instructions, after an hour or two of run time, the compression will increase as the piston ring starts to form.

http://www3.towerhobbies.com/cgi-bin...+kit&search=Go

i once had a supertigre 50 that had not been used in over a decade, not have much compression ........ After i fired it up the ring perhaps loosened up and it was back to normal

If you have an electric starter try to run it and see if it loosens up

I think you have gotten some good responses here. I'll pass along a tip that my very knowledgeable dad passed on to me. Inject some heavy (castor/30 wt) oil into the cylinder. If the compression improves it the rings, if not it's the valves. This is from a man who could rebuild a four cylinder Model T to a 1710 c.i. Allison V-12.

Bill

A month ago I replaced the ring and bearings in a OS .91 four stroke. It had a little compression before running. After running for a few minutes, the compression was much better and kept getting better up to a point the more I ran it. Now it has as good compression as it had when it was new. It just may need some time to run in.

I've never had an NIB OS four stroke that had "inadequate" compression. If the engine is old and it could be almost 20 years old, the 120S-E was released in 1989, it might be dry. If you haven't already, put a few drops of oil into the cylinder. The comment about the throttle being closed is valid and check that before doing anything else.

Surely you jest. It has to have some compression in order to start up and run.

CR

Thanks to all the experienced glow guys that responded to this thread for all the valuable tips and information.

I suspect I had the 'dry engine' syndrome as a I put a few drops of After Run oil in the cyclinder, rotated the prop back and forth and then let it sit overnight.
Next day I made sure the throttle was open, put the plug back in and guess what - like magic - I had good compression!

Again, many thanks to all the contributors for helping out the new RC Glow guys like myself. I can sleep a lot better now!

Ken Cz

Another success story.

We can sleep better also