a 1989 honda foreman 4x4 trx350d

have a couple of questions that i hope members might be able to help with i own a

a 1989 honda foreman 4x4 trx350d

#1 would any one here no the plug gap size

#2 the engine seems to get realy hot to the piont your legs feel as though there burning

#3 yesterday when i started it was running for a bit then when i reved the engine it mad a bad knocking noise hard to say if its top end or more in the center of the engine
it seems to have stopped now but am not sure if i should be looking deeper into it

thanks for any help