Tractor Repair: battery on lawn tractor, fuel situation, valve seats

Question
Hi Danny,
My son bought a lawn tractor at a garage sale for $50....that pretty much says it right there. :-)  Actually, it ran fine (a little rough on startup) but other than that fine.  The guy he bought it from said to use unleaded gas, so we filled it up. It wont run now.  Also, I went and bought a new battery for it, and took off the old one without watching which wires went to pos/neg...there are no markings at all...all wires are red.  I can tell you this much from looking down at it:  there are two wires on the left side, one that goes thru a little black part to the engine light, the other goes directly to a wire into the engine.  The wire on the right goes directly to the frame.  I dont want to make any assumptions and blow this thing up, so can you please tell me how to hook this back up?  The only markings on the tractor say 11 hp 3 speed turf trak...it is pretty old...maybe 70-80's ? And is it correct to put plain unleaded gas in the engine?  Thank you!

Answer
Wendy the fuel situation is.Here in Australia we have an additive you can put in the unleaded fuel to help that you do not damage valves and valve seats.
The name of this product is Nulon lead substitute have a look at there web site www.nulon.com.au
The other thing with not starting after filling with unleaded fuel is that if the fuel was not new eg you had a drum in your shed it could be stail as unleaded fuel can not be stored for long periods.
Or you may have flooded the motor it may need spark plug to be replaced or cleaned.
The battery issue the lead that hooks to the frame the right hand one this would as a rule be the negertive or earth lead.
Hope this helps with the problems you have.

               Kind regards Danny Last