I have an 86TRX 350 starts great cold, but as soon as you start to ride it it powers out and dies (just like running out of fuel or seizing from heat) It takes only 15 seconds to 1 min. for this to happen. I have:
*ran it with aftermarket fuel pump from external tank
*Checked valve clearance (.006 & .009)
*changed carbs with a (supposedly) good one
*lots of oil pressure
*changed coil with a known good one
*replaced spark plug

I also have a good running '90 300trx...
any help would be appreciated