Manual for briggs and stratton 12000 series mowers quantum

Start here with complete model number..
http://www.briggsandstratton.com/us/en/support/manuals

you can order one from your local briggs dealer. what information are you looking for?

The filter is right at the Prime bulb.

Hi - you can download manuals for all current and the vast majority of older engines direct from the Briggs website (owner/maintenance manuals and Illustrated Parts Lists) . You can also buy proper 'strip down and repair' manuals from Amazon among other places. Note - these are official publications and it's unlikely you will find them for free (they're illegal if you do!).

sae 30.

Do a compression check when cold, then again when hot. Sounds like when its hot your losing compression. If this is the case, it won't want to start when hot. Compression should be above 60 lbs. Thats where i would start. I hope this is of some help to you.

Sounds like you will need to clean your carburetor.
Sometimes you can get by with priming it a few times, and letting it
run a few times like that and it will flush the gunk out of the jets,
but most of the time you will need to rebuild the carburetor.
If the mower is over a couple years old, then I also recommend that you
buy and install a new carburetor repair kit, because the diaphragm will
get hard and that will cause it to be hard to crank.
When you clean your carburetor and remove the jet screws, count the
number of turns it takes to seat the jets from their original position.
That way when you go to put the jets back in, you know how many turns
they were in/out.
Please rate me, Thanks
Good Luck, I hope this helped

if cable is all intact, just hook it back up, if broken, then replace it.

There should be a drain plug on the underside of the mower deck. Raise that side of deck, remove the plug and drain the oil. Replace the plug and add new oil. Hope this helped.

Home Depot has the plug you need for briggs 6.5hp engines. Don't worry about it being a Murray. Buy a Briggs 6.5hp plug.