what to know about 706

You are going to like that 706. I bale hay in the summer and use mine when I need to round bale some. Other wise I use my 400 for square baling.
Fuel usage is the only issue I have with it. Other wise you get all the modern features you want at a cheap price for the HP.

uses the C263 gas engine same as the 560 just more rpm's. One thing try to use 93 octain gas as the C263 likes to burn valves. The guy that said 1000 hrs till rebuild is full of it.
If you treat her right she will treat you right for 2500 to 3000 hrs.
After that you can repower for a song. Almost any engine from a 460 to a 301 combine engine will fit. $300 to $600
Or rebuild it your self. for about $1300 I redid mine complete. Pistons, rings, all new bearings, reground the crank and got the head rebuilt.

Oil leaking past the valve stem seals is cooked on the valve stems leaving carbon deposits. as long as engine load conditions remain somewhat constant this is not a problem. Increased load on the engine will cause valve temperatures to rise which causes the stem to expand. The added carbon deposits on the stem can cause the valve to hang open for a fraction of a second longer than normal but that is all it takes for the exhaust gasses to ruin the valve. Under load the valve is running at tempuratures that are nearly red hot. A missfire caused by a valve hanging open means that the oxygen was not used up on the combustion stroke. This oxygen can then burn the metal in the valve. It is not unusual to see a valve that looks like someone took a cutting torch to it.

(Cub Cadets can suffer from the same problem when the guides get worn. The engines dies under load and will not imediately restart. Within 30 seconds you will hear a little ping as the valve closes and the engine will restart.)

Being a little abusive to the old red tractors, 'taint ya? :>)

Allan