classic motorcycle forum

I just had my 69 Triumph 650c motor rebuilt. It actually ran when I pulled it out but was starting to smoke and leaked oil bad. I put the motor back in and it will not start. It backfires through the exhaust like a shotgun blast. I run the boyer and have done all the testing to make sure it checks out. I've also rechecked the static timing, it to lines up. Plenty of spark, gas, and batteryvoltage. Can somebody please give some advice on something I might be overlooking?