twraska - 11/10/2010 21:09

The 630's had an automatic fuel shut off on them, worked by engine oil pressure. This kept the fuel out of the engine when stopped. The carb's fuel needle was never real good at keeping the fuel shut off. It was a steel needle on a brass seat. Later some had a rubber tip which held the fuel but tended to stick shut, so choose your poison. With that said, I'd still say you have a bad carb. Does it have a gasket under the seat preventing the fuel from going around the needle? The needle should hold the fuel at bay for at least a few hours unless the float is bad. The load needle can be 'broke' in that the top cone came off and is stuck in the carb body. This will make the engine run BAD and lack power.

The backfiring sounds like an ignition problem. Maybe a bad distributor cap, timing issue or advance not working properly. Now if the issue is missing out under load but idles OK then it is probably some internal passages blocked. Most likely the ones under the small 'freeze plugs' on the side of the carb.

I have followed your problems over the past few weeks, don't give up on it. It will still do it's share of the work when you get it going right. I learned to drive on a 630, started farming with it and my son still has it. They were pretty good for their time,