Tractor Repair: JD 2130 Tractor firing order, rocker shaft, vintage club

Question
i have a JD 2130 that is backfiring very badly. not sure if the kids mixed up plug wires. can you tell me firing order for distributor and engine? how should timing be set?
where can I find this info on line other than bugging you guys?
JD website not very helpful.
regards, Roger

Answer
i take it its a gas engine i have never worked on these.the leads on the engine should be run in such a way that their length matches their cylinder.with the engine running remove momentarily one plug at a time and listen to see if it drops a cylinder.im thinking you might have a problem with valve adjustment or a broken rocker arm.have you inspected the spark plugs as maybe one isn't firing atall.first make sure that they are all sparking then try removing the plugs one at a time and listening to the change as i said if you get the same sound for every plug you remove(replace before removing the next one)then they are most likely on properly lastly remove the rocker cover and check for broken rocker shaft or arms let me know if none of these helps and i will try help further.i do not know of any better place to get info but there are lots of tractor forums you could join and be able to get info from other owners try google your tractor with the words forum or vintage club if you join one of these you can post your questions to other owners
when i say remove one plug at a time i mean the plug lead and not the spark plug as you would blow your head off