I recently got an OS 35 S used that has been reworked by Big Art. The case on this one is a disaster, one mounting hole is missing, the rest are drilled all screwed up. I have a case in great shape so I want to change them. I've never done this so how about a correct order in which to do the swapping of parts. Also any other tips and proceedures I should follow will help a lot. TIA

1. Put an old prop on the engine and tighten it.

2. Removed the head.

3. With the piston at the bottom of the stroke, put a Popsicle stick into the exhaust opening. Rotate the prop until the piston traps the stick between it and the liner. Continue to rotate the prop until it pushes the liner up in the case. If really tight, try heating the case around the sleeve area (monkote gun or hair dryer works) until the sleeve is free.

4. Remove the back plate.

5. With the sleeve removed there is enough room to work the connecting rod off of the crank. Again it's easier if you have the piston near the bottom of the stroke bottom but skewed toward the transfer port a bit .

6. Remove the prop and pull the crank out of the case from the back. If the drive hub is stuck, a light tap with a piece of wood on the crank end should break it loose. Hold you hand over the rear of the engine to keep the crank from popping out on to the floor if you have to hit it.

Clean up the exterior of the sleeve while you have it out. Oven cleaner, Crockpot, fine steel wool all work pretty well.

Reverse the order to assemble and use a small amount of oil on the sleeve  and be sure that it is free enough to be rotated while in the case. Air tool oil works well for this plus it is good for storage. The sleeve to case is a slip fit.... not a press fit and you will have to rotate the sleeve to position it properly after it's in place. Pay attention to which port is the exhaust and which port is the intake. I don't remember if the engine case has a position pin for the sleeve or not... I don't think they did.

         

Thanks Dick, thats what I was lookin for.

Hi

You won't have much problems  the OS 35 is  is  NOT a  press  fit  sleeve, they normally  come apart very easy, just follow the instructions already written. Write back how the job went

Regards
Randy

New and old

Just ran it and it runs great. I've just got a cheap Tower tach but it showed 9800-10,000 just before the break using a 10-4 Top Flite wood prop.  Thanks again for the help.

HI Lee,

All sounds good to me!  Just get her in a plane and prop it to that plane.  It should be a very good engine for you.