Get some wet-dry paper. 600 grit spray it with CRC. Or use a hone. Keep the CRC up to it.
Rub the worst of the scuffing off the bore and the piston.
Clean the ring groves out on the piston with a small screwdriver. The grooves will be full of carbon.
Take care not to wash too much grit etc into the crank bearing or up in the small end of the conrod.
Wipe the motor out with a clean white rag and warm soapy water. Not that it really matters that much. The soapy water that is, if its scored up any grit thats left over will hardly hurt.
Go to the mower shop, buy a new set of rings, head gasket, pull starter O-ring and both inlet o-rings and a stop pin rubber. The whole lot should be well under $50. (and carb stuff if you need it, primer face and O-ring and needle, another $20-25) Put it back together and i bet it runs a treat. They are not a low tolerance technological break through. They will slap and rattle away, they dont need heaps of compression, a few scuff marks wont hurt.
Slop a bit of 2T oil about in the crankcase (into the crank and big end bearings) and in the cylinder when its going back together. Say about half a cap full or a bit less, most of it in the crank case. It will smoke like no other when you start it.
Heres a tip, put the bottom ring on, then put it in the cylinder, then once thats in the cyl, put the top ring on and push the piston in. That will save your fingers. Doing both at once, when the bottom ring gives your fingers that were holding the ring into the pistong groove get jambed between the top of the cyl and the top ring and it draws blood and in nasty spots on the tips of your fingers. Rings are sharp.
Biggest hassle is the conrod pin/bolt. If you can get that undone and do it back up with the same method you are a-rockin. I did one with a pin punch years ago. It lived out in the weather for 8 years that mower. Got a bit hard to start, i thought it was going to have to go to heaven, thats why i bought some mowers and started fixing a few to fund a free rebuild on mine. All i had to do was clean the carb out it ran like a treat and started first pull, then i sold it.
Play in the big end??? when the roller pins fall out of the bearing its probably got too much play. its got to have play for when it warms up so it has room to expand.
What i would check is the play in the bottom bearing in the crankcase. Grab the blade disc and see if it has any movement.
Before anyone goes telling me im a rough bugger, i know i am. Ive got a few Cyls out in the shed that look like the one i did years back that i mentioned above and probably aldots too. It works, it will mow and do the job. Ive got a selection of better cyls here so i have no need to do that. If you have only got the one, then thats all youve got.
Cheers, Bob.
