Craftsman 6.0 HP Self propelled/Mulcher lawnmower. Model# 517.372500 After starting and cuting a couple of strips... oil starts to blow out the breather tube, white smoke starts to come out the other side of the mower, so I stop and reload oil.

What is the problem and should I start looking for a new one (mine is 15yrs old) or can I repair myself. Other than this it cuts like a charm...

If anyone could help please let me know. I would appreciate it very much.

LdyJazz

Sounds like either a faulty or gummed up/worn out breather (which does happen, they do wear out etc.) gas in the oil (which it would smell like it) or (side valve engine? You know L head, flat head?) shouldn't be a head gasket then.
I'd replace the breather and see where that takes you. What weight oil are you using? Straight 30? Or multi weight conventional?

I have a 10.5 hp B&S on a Rough cutter by Swisher and it was blowing oil from the breather tube into the air filter and then being sucked down the carberator which caused it to stall it was getting so much. I took off the breather and found oil in the carberator 1/2 deep. I soaked it up with a rag and then restarted it, that is when I found out the oil was coming from the breather tube like a GYZER! Spewing everywhere! I was researching online as I always do when I have a problem I can't solve. I had read quite a lot of solutions but decided to try the "O" ring seal on the oil dip-stick. WHA-LA! I actually went to my local auto-part store and bought some "O" rings that were supposed to be for a GM Distributor. They jusy look like they would fit and I tried it and it solved my problem for $2.99! Better than replacing head gaskets, stuck valves or bad oil rings in the combustion chamber which were the other solutions mentioned in solving my problem.

I am having this issue right now. Why would a faulty o-ring cause oil to come out of the breather? It's not gushing out any more but it is "spitting" oil out of the breather. My o-ring seems to be fine, no crack, the seal looks good.

Check your owner's manual to make sure you are tipping it correctly when doing maintenance on the underside. My Briggs&Stratton engine TroyBuilt walk-behind mower specifically states to tip it over with spark plug towards the rear or up and the fuel tank empy... not how I would normally tip up a machine. This is especially true if I were to discard the old engine oil through the fill tube rather than the hard-to-locate drain plug on the underside of machine. It states that "if the fuel tank is not empty and if the engine is tipped in any other direction, it may be difficult to start due to oil or gasoline contaminating the air filter and/or spark plug." I had this problem not realising I was tipping it wrong, of which I often do to remove stuck on grass cliippings due to cool-season grasses which take a long time to become dry during the day due to spring rains and thick stalks. I'd often see white smoke after cleaning underneath it. The tube breather on my machine is thin and already cracking after owning the model 860 for two years now. Got some replacements coming in the post.