I have an OS91 4-stroke with a cracked case. Don't ask. Oh well, someone took off the right wing of my 4*60 in the air. I thought I was an ok pilot, but I couldn't keep it flying with half a wing. How do you remove the cylinder liner without damaging it? The internals all look ok. A new case is $85 but not sure if it is worth rebuilding at that price especially if anything else needs replacing. Anyone have a case that they want to get rid of?? Thanks.
John VB
The liner on the .91FS I took apart last summer simply slid out with very little effort, once I removed the head.
Hi,
It should slide out once the head is off. You can push from the bottom with the case back off. Soak it with automotive "fuel injector and carb cleaner". If it is still too tight, heat your oven to about 225 and put it in there for about five minutes. Use oven mits and try to get it out while the case still hot. This will also permit you to remove the bearings with ease. However, new bearings (Boca Bearing) are inexpensive - I would use new bearings in the new case.
If the impact was great enough to crack the case, before you spend $85 for a new case, you should use a caliper to measure the sleeve to make sure it is still "round" and doesn't have an inner surface gouge from piston slap. Also, you should check the crank for run-out if the prop shaft took a direct impact.
It is a little tricky to get the valve timing mark lined up during re-assembly. Double check it when you do the installation, because it has a tendency to be one tooth off when you slide in the cam assy.
If you don't need to replace any other broken or worn parts, $85 is sure better than the new price.
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