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Hello all

i have recently bought a second hand McCulloch M46-500 which has a Briggs & Stratton series 500 engine.

in using it for the first time, it started well, but as I went through more dense grass (no hugely long - newly laid lawn approx 6 weeks old) it stopped self propelling - so I thought I would have a look!!

i tipped it on its side , carburettor side up. I noticed that the drive belt guard was broken, and the pulley in the gear box was heavy with grass, which I cleaned out. I then took the blade off (in order to take the guard off. To take the blade of I used a set of grips on the in blade support to get some purchase, then removed the centre bolt.

I then put it back together in the reverse order, but trying not to over tighten the blade.

to my horror when I put the lawnmower upright again there was a lot of oil dripping down the chassis, from the exhaust region, onto my brand-new patio (my wife doesn’t know this yet!).

I wpied up the oil from around the engine and where it had pooled on the chassis. UnSurprisingly when I went to start it it would not start, and the pull string was hard to pull, with a lot of vibration.
I did some googling, and as a result when I remove the spark plug it was a lot easier to pull over. I cleaned the spark plug and tested it and there appears to be a small spark. I took off the air filter, that was saturated in oil. I removed it and the air filter housing and clean them out. I could see by pressing the priming pump that there was fuel going to the carburettor.

in a bit to clean out the chamber I pulled it over number of times without the spark plug in. It pulled over easily with some resistance, I also put my thumb over the spark plug hole I could feel pressure pushing my thumb back when pulling over. However, when I replaced the spark plug it was tough to pullover and there was some knocking noise from underneath (Felt like the blade was vibrating?)

so today I’ve had another look, I tipped it around 45° this time to have a look at the blade. That seemed loose I could move it very slightly backwards and forwards without it moving the blade support. I therefore tried to tighten it up once more. In doing so when I tighten the bolt (with the blade jammed), The whole mechanism turned clockwise, therefore I was unable to take any further.

when I put the mower down again, once again I had some drips Of oil, not nearly as bad this time.

so that’s where I am, so I’ve what Have I done wrong, and how do I fix it please? If pictures would help let me know.

any help appreciated guys
Locksnapper.

Lets start with the model number of the briggs engine. Depending on when it was made could be located above the spark plug, on the flap above the muffler or the newest location is on the side of the block somewhat obscured with paint.

Thanks @ILENGINE do these attached pictures help?

I suspect what has happened is the breather is on the muffler side of the engine opposite the carb. when the carb is turned up it puts the breather on the downside which then fills with engine oil. Then after the blade was installed it was set back down level, but the breather is still full, and when cranked crankcase pressure pushed the oil out of the breather through the breather tube which connected to the carb. Then is basically pumped into the engine through the carb.

I always tip the mower so the spark plug is up. Not the handiest way to get under the mower sometimes but avoids all the mess.

I will take that on board for next time Tom.
@ILENGINE , in that scenario, how do I clean the oil out of the breather pipe (and any subsequent movement of oil)?

Most will drain out if the mower is setting level, But the fastest way is to keep cranking the engine and getting the oil out of the cylinder which may require installing and removing the plug a few times, and then when it starts just run it, Make sure the oil is at the proper level before starting to prevent a low oil failure.