4 Stroke Lawnmover

[squareflops]

I'm at a bit of a loss on this one.

Just inherited an old (leaded age) lawnmower and decided to freshen it up with a service. I decided to do this after cutting the grass as wanted to get that done early. The air filter was filty so I washed and re oiled it. Fine. then i checked the plug, which was loose so tightened that and then on to the sump oil. I emptied just about exactly 500ml from the sump. However when refilling the filler only seemed to take 300ml. How odd I thought. Whatever I did (tipping it on its side, turning it over slowly) the level stayed near the top of the filler neck. At this point I ran it for about 20 seconds. It didn't sound like it was running dry but I decided to knock it off anyway. I then went back to the filler to 'top up' and noticed that however much I put in; it didn't actually overflow. It was like tipping water into a toilet, no matter how much you put in the level remains the same. I put in the full 500ml and ran it. Now after about 30 seconds it starts smoking its chuff off from around the exhaust/head area, whicj it wasn't doing before. This is telling me that its running too hot i.e. not getting the oil feed??? (I haven't spilt oil on the head whilst doing the change) Im reluctant to run it any more as I don't want to cause permanent damage.

Think i've been thorough in my explanation.

Whats wrong with it??

[Dogwatch]

Sounds as if you have overfilled the sump and the crank is thrashing around in the oil instead of just above it.

[squareflops]

Yea considered that too. But 500ml came out and 500ml went in.

Frustrating as I can service my BMW but not my lawnmower!

[sparkythecat]

I think that tipping it on its side, has caused the sump oil to run up past the piston rings.
It'll stop smoking eventually, but will probably oil the plug up.

[squareflops]

Think you may have it there Sparky, i'll give it a good run and hopefully it'll survive