Os 91 4 Stroke Engine Driver And Placed

Since you have now cleaned up every thing, it should work just fine.

This morning I decided to fix the broken prop and take the Cub flying.

In getting the plane ready I decided to fire up the engine before leaving for the field.

Listening closely I heard, sort of a soft, not metal to metal, but noticeable, funny sound on each revolution.

Since it had no compression I thought the problem might be one of the values were stuck open from sitting over the winter.

I took off the rocker cover and found only one of the rocker arms were going up and down.

Os 91 4 Stroke Engine Driver And Placed

I took a small screw driver and placed it under the rocker that wasnt, gave a little push and sure enough it POPPED up I then tried to turn the engine over but found it would not make a complete revolution in either direction without hitting something and stopping completely Its hitting something hard.

The only other thing I can think of is a failed bearing due to corrosion jamming the works and that would require total disassembly, bearing replacement, re-assembly, timeing ajustments, etc,etc Im guessing, but posted anyway Roger aka GIFLYRC.

Remove the glow plug first and remove the intake manifold and the exhaust pipe.

Might have to tap it gently on the side to get it to release.

There is a shim too so watch for it as the head comes off, it usually sticks to the head pretty good.

I would cook the head in warm (hot but not boiling) anti-freeze for 8-12 hours.

You may find the valve stems, especially the exhaust valve may have a build up from using Castor oil in the fuel.

Clean that off. Be very gentle around the valve faces, they can be damaged easily.

Check the valve springs to make sure a spring has not broken but I doubt it.

Oil up the whole thing, reinstall it, tightening the screws across from each other to keep from warping the head.

You will have to realign the valve pushrod tubes but that is not hard to do.

Since you did not change the timing, you do not have to worry about that.

Once it is all back togehter, turn it over by hand to make sure everything is moving like it should.

This is sort of a top end overhaul though you have not replaced anything, you have just cleaned it up.

Do not try to lap the valves, the materials are very soft and can be damaged easily.

Being soft a few hundred revolutions of the engine is enough to reseat them should you take them out.

I am guessing it was a stuck valve that was keeping the piston from completing a cycle.