I'm looking for a second opinion on some issues I've got after rebuilding a 19.5HP single cylinder Intek engine, model-type-code 31P677-0138-0907....etc.
The cylinder was honed and new rings put in, and the top main bearing sleeve/insert under the flywheel was replaced. Around 10 hours of operation after the rebuild, the cylinder walls are scored at 9 and 3 o'clock looking into the bore from the head side (image 1, 2). The scores aren't deep - I can barely feel them, and a 0.002" feeler gauge feels massive in comparison - but they still shouldn't be there I think. This engine is on a Greenfield ride on and it did at least an hour of real hard work cutting tall grass at around 2-3 hours after the rebuild.
The scores/scratches are clearly a result of wear between the piston skirt and the bore - they stop before the rings do at the top of the bore.
So far I've put it down to not cleaning the engine well enough after honing before reassembly. All the advice I read (now) is that the bore should be thoroughly washed in hot soapy water and then wiped down with oil or similar - my cleaning procedure wasn't so good in hindsight. All I did was wash the bore with cold water and detergent, and didn't pay much attention to the rest of the engine block beyond making sure there was no visible honing grit in it. Then, of course, I did a poor job of drying the bore and forgot to oil it, causing it to rust slightly. This light rust came off easily with a bit of fuel on a paper towel, but I didn't do any more cleaning beyond that. It looked clean, but now I suspect it wasn't.
I changed the oil at the 6 hour mark and what came out looked pretty nasty (image 3) with lots of small specs and filings that are attracted to a magnet. The engine has an oil filter but is not pressure lubricated (the oil pump just circulates oil through the filter).
My question is, do you think this sloppy cleaning procedure can be blamed for the scoring and metal in the oil after running the engine for a few hours? At this stage I can't see anything else that would've caused it.
Thanks in advance, RLP
Last edited by RLP; 30/06/1907:06 PM. Reason: Change wording
