[Kennuck]

Originally Posted by 88Stanger

I am sure you know that the piston will come up twice to the top, once for compression and once for exhaust. I have done the finger in the hole and waited for poff on the finger only to discover later that it was on the exhaust lift and we were 180 degrees out on timing, just trying to help. sometimes simple things can get us.

x2
A finger in the plug hole is not a good way to determine TDC on compression stroke. You're likely 180 out, backfire through carb is classic symptom 180 out. Give it a try its easy to do and will likely fix your problem.