Have changed the head gasket on a Fiat Cinquecento Sport.Have set the timing, turns over but running rough.?

Backfires through carb. Anyone ever come across this, and how do I solve it, please?????!!!!!Have changed the head gasket on a Fiat Cinquecento Sport.Have set the timing, turns over but running rough.?Sounds like the timing is not quite right and letting hot gasses back through the inlet. Maybe just one tooth out
Have changed the head gasket on a Fiat Cinquecento Sport.Have set the timing, turns over but running rough.?
sounds like the timing is out by a few degrease and or an air leak on the inlet manifold recheck your timing and the inlet manifold also make sure all the vacuum pipes are attached in the right places all so the ht leads
Have changed the head gasket on a Fiat Cinquecento Sport.Have set the timing, turns over but running rough.?
when you reset the ignition timing it is almost certainly 180 degrees adrift and trust me it will be more than one tooth out
There could be 2 faults here

1 timing not set correct

2 plug leads wrong way around