my honda 300ex bogged down and started rapidly backfiring the other day, it died, i choked it, it cranked it had good power on the bottom end, however it had no power on the top end, it would just bog on the top end, i got it home, and know it wont crank...any ideas what the problem might be?

 

I dont know for sure ,but back firing alot sounds like timing (timing chain )
.
there is a adjustment on the 300ex ..but I dont have my service manual to tell you how to do it properly...
.
if you cant adjust it out .id advise replacing the worn parts(my timing chain guide broke last weekend and put the valves through the piston)on my 300ex