[AT] John Deere power unit

[Greg Hass]

At an estate auction recently my brother bought a John Deere LUC power 
unit that had been on a pull type combine.  It was sold as is because 
the mechanic hired by the family to get everything running had been 
unable to get it started. The mechanic said that it had spark, but that 
an exhaust valve was stuck open but he ran out of time to go any 
further. After getting it home, my brother was able to get the valve 
working without removing the head. The gas bowel was leaking gas to bad 
to use but he was able to get a little smoke by squirting gas in the 
carburetor,but after fixing the bowel gasket; no fire. I helped him take 
apart the carburetor and we could tell the previous owner had never 
gotten it running, although it appears he tried as it had a new muffler, 
had been nicely painted, and he had made a new gas bowel gasket 
(unfortunately he made it out of corrugated cardboard,thus the leak.) A 
few days ago my brother installed a kit in the carb and cleaned it up. 
He has gotten some smoke out the exhaust and also actual fire out of the 
carb; the air cleaner is unhooked while he tries to get it started. I 
was there a couple of nights ago when he cranked it any we both think it 
is a timing problem (could be bad valves but we don't really think so at 
this point.) The problem is,at this point we have no idea of what the PO 
might have done. Did he have the mag out and got the timing off putting 
it back on, is the mag tilted wrong, are the wires reversed; or is the 
mag off half a turn? Also we don't understand this engine as to how it 
fires. Is it even or does it have that odd JD firing order; we have 
always been IH people but lately my brother has started jumping ship. My 
question to the list is this; any help on how to set the timing on this 
engine would be greatly appreciated.
                 Greg Hass