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Am having a #3 cylinder problem on the O-200. Would welcome suggestions.
Installed a used cylinder on #3 after having new valve springs installed, valves and seats either ground or replaced as needed, cylinder was honed 0.015 oversize and installed new 0.015 rings on servicible 0.015 piston. Piston had previous 200 hours in service and was in good shape with no apparent wear. After 2 hours since the cylinder work was done, cylinder #3 is pumping oil, enough to foul #3 lower plug after 2 trips around the pattern. Clean the plugs, normal mag drop. Then mag drop after another two trips around the pattern degrades to 400 rpm drop on left mag with considerable roughness. Right mag drop remains OK. Plugs, mags, and harness are new. Pulled the cylinder this afternoon and the dorsal and ventral sides of the piston between the #1 compression ring (top ring) and the top face of the piston are showing substantial wear; enough that I"m going to replace the piston. My first thought was that the cylinder may have been bored considerably too much oversize, thereby allowing the piston to slap vertically (rocking on the piston pin), but I haven't had the dimensions checked yet. Will have that done in the morning as well as checking for cracks inthe cylinder. Are there any other obvious possibilities that I may be overlooking?
To summarize, recent cylinder work, pumping oil onto the lower sparkplug, piston damaged after 2 hours in service. Piston rings, ring grooves, lands, and skirt look OK, as does top of piston, but piston itself has obviously been rocking severely n the last two hours.
Would appreciate any input.
JimC
Installed a used cylinder on #3 after having new valve springs installed, valves and seats either ground or replaced as needed, cylinder was honed 0.015 oversize and installed new 0.015 rings on servicible 0.015 piston. Piston had previous 200 hours in service and was in good shape with no apparent wear. After 2 hours since the cylinder work was done, cylinder #3 is pumping oil, enough to foul #3 lower plug after 2 trips around the pattern. Clean the plugs, normal mag drop. Then mag drop after another two trips around the pattern degrades to 400 rpm drop on left mag with considerable roughness. Right mag drop remains OK. Plugs, mags, and harness are new. Pulled the cylinder this afternoon and the dorsal and ventral sides of the piston between the #1 compression ring (top ring) and the top face of the piston are showing substantial wear; enough that I"m going to replace the piston. My first thought was that the cylinder may have been bored considerably too much oversize, thereby allowing the piston to slap vertically (rocking on the piston pin), but I haven't had the dimensions checked yet. Will have that done in the morning as well as checking for cracks inthe cylinder. Are there any other obvious possibilities that I may be overlooking?
To summarize, recent cylinder work, pumping oil onto the lower sparkplug, piston damaged after 2 hours in service. Piston rings, ring grooves, lands, and skirt look OK, as does top of piston, but piston itself has obviously been rocking severely n the last two hours.
Would appreciate any input.
JimC
