I have been working on a very old 680CK. I rebuilt the cylinders on the hoe and have used the backhoe a little bit around the property. the problem is that it starts really hard and I have to use a charger because I have to crank it for so long. Once it fires up you can hear that two of the cylinders start to fire up after it is running a bit. like the fuel is just getting to those cylinders. (sounds like when you put a plug wire back on a 4 cylinder 4 stroke when it is running). I bleed the lines and it looks like i can see little bubbles on the line for the cylinder that is furthest back on the tractor. Why would there be bubbles in one and not the others? is it a bad lip seal or something? has anyone had that problem it is a A267D probably around a 1966 vintage. once those cylinders fire she runs very strong.