I recently purchased a 1950 John Deere B. It has smoke coming from the clutch assembly and I was informed that there could be two things causing this. Either the vent pump on the fan shaft isn"t working or I have blow by from the pistons. I checked the compression and I get 60psi on each cylinder. From what I have read the "All Fuel" engines should be around 70psi and the regular gas models should be 110 psi. My tractor only has one fuel tank and nowhere does it say "All Fuel". Is it possible for the compression to only be half of what it should be if my tractor is not an All Fuel? It runs well with no smoke other than white smoke coming from the clutch pulley. I have the head off now and I will do rings if needed, but I don"t want to open a can of worms making repairs if I don"t have to. Any suggestions???