632 engine backfiring

[BobMn]

Hello to all; Been a while! The new hyd. motors are working grt. New hoses (FUN) O rings, filters, fuel shut offs (SPENDY) points, plugs, wires, and carb rebuild. This has to be the cold bloodest? engine I have ever had! The choke has to be out almost always. (northern Mn). As it warms up it is somewhat better, but not much. I was told the Ford engine is this way, with the up draft carb. Any one know about this? It "pops" back though the carb,killing the engine, like its running lean....I set the float to the service man. specs. thanks much Bob

 

[Tazza]

It could be running lean or the timing may be advanced too much? Could be red hot carbon on the plugs or on the head causing pre-ignition. A valve stuck open could do it too. Check your dizzy, could be cross firing?
Have you checked your valve clearance?
I'm sure these things may sound stupid, but it never hurts to state the obvious, it may have been over-looked.
As far as i'm aware, even an ice cold petrol engine should start without this much effort. Diesel on the other hand will not....
It should not need to run with the choke out either. It should just need that to start and warm then after that it should run without. With running it with the choke on you will be using more fuel and will most probably give you less power and usually blows black smoke. I remember i had a rider mower that would conk out if i didn't have the choke on a bit, i had the high speed jet set wrong, it could just be an adjustment.
These are the times you wish the engine had fuel injection, it would save you so much effort. Easy starting, no tuning, PERFECT.