SOME ENGINE HELP PLEASE

Ok gents give an 85 year young feller some advice.on craftsman 970917707,16 hp Briggs,,mod.L8U707,type 1174E1.Problem in nut shell,it smokes a bit while engine running,only some times thou.It may blow blue smoke out exaust for 15 sec. then clear up. After a bit.engine starts and runs like a clock.only thing i noticed was plug get good bit of junk on it,i clean it off and it runs fine.when it starts smoking it will do it on level ground or up or down hill.engine never quits or stalls.give me some things to check out.and what plug belongs in that engine?oil seems to be at mark on dip stick,stuff so clean is hard for my eyes to see.give an old goat some ideas what to look for.Paul

aka, Basic checks. Compression check. Go buy a cheap gauge and follow instructions. Sounds like worn cylinder, rings. Possible valve guide wear or guide seal wear.

My daughter had a Craftsman mower that did the exact same thing. Pretty sure it was a Briggs engine.

It was an old mower she bought for $10 and used it for 2 1/2 seasons until she sold the house and the mower went with it.

I was going to open it up during the winter and take a look. I suspected valve guides or something haywire with the crankcase vent system but never got the chance to take a look.