I inherited a 1948 8N with a front mount distributor. Electrical system has been converted to 12volt and has a 12 volt coil.
engine was rebuilt in the mid 90's, run for a couple hours and then sitting ever since. (if I remember correctly the head was retorqued several times to ensure proper bolt torque. I have also retorqued the head after the first run, with no looseness noted
When cold, engine starts and runs good for about 5 minutes then begins to run extremely rough at idle and about 1/4 above idle. Have to pull the choke out slightly to keep it running. As RPM's increase, the engine runs a lot better and the choke can be pushed in. At full throttle the engine runs fairly well but has a slight sputter (no backfiring). Have noted that when the engine is loaded the the sputter stops from about half to full throttle and runs better at lower RPM's, but still needs a little choke at idle (loaded by simply applying the breaks enough to put a little strain on the engine). When the brakes are released, the sputter immediately comes back
the tractor currently has new plugs (properly gapped), new points (properly gapped and checked on 2 different occasions, along with timing), new condenser and new 12volt coil. There were some extra parts kicking around so I installed another coil and condenser to rule those out with no change). Also briefly jumped the ignition switch to rule that out, and briefly took out the coil resistor to check that... no change. spark plug cable installation / firing order has been confirmed, no issues. When spark plugs are removed they have a nice dry "tan" color which looks pretty good to me.
Checked the fuel system and gas flows from the carb drain plug without issue and all filters / strainers are clear. The carb was new when the engine was rebuilt... I have it apart now and soaking but all the components look very clean so i don't think that was the issue. Air cleaner has also been cleaned
I had already checked for carb / manifold leaks with a propane torch but did not note an improvement when propane was flowed around the flanges. Tried adjusting the idle mixture screw (currently 1 turn out) but no improvements
Compression dry is 115, 106, 116 and 118. Wet compression numbers went up a little bit (roughly 4 to 5 psi) indicating that the #2 cylinder probably does not have a valve issue, but is still weak compared to the others. Do not have any indication of a head gasket leak at this point. Also have checked valve clearances, intake and exhaust were in spec per the manual on all 4 cylinders
Any suggestions?? not a 8N tractor expert, so having a hard time figuring this out.
I have not removed the governor yet for inspection... but there is no "hunting" so I am not sure that is the problem either
engine was rebuilt in the mid 90's, run for a couple hours and then sitting ever since. (if I remember correctly the head was retorqued several times to ensure proper bolt torque. I have also retorqued the head after the first run, with no looseness noted
When cold, engine starts and runs good for about 5 minutes then begins to run extremely rough at idle and about 1/4 above idle. Have to pull the choke out slightly to keep it running. As RPM's increase, the engine runs a lot better and the choke can be pushed in. At full throttle the engine runs fairly well but has a slight sputter (no backfiring). Have noted that when the engine is loaded the the sputter stops from about half to full throttle and runs better at lower RPM's, but still needs a little choke at idle (loaded by simply applying the breaks enough to put a little strain on the engine). When the brakes are released, the sputter immediately comes back
the tractor currently has new plugs (properly gapped), new points (properly gapped and checked on 2 different occasions, along with timing), new condenser and new 12volt coil. There were some extra parts kicking around so I installed another coil and condenser to rule those out with no change). Also briefly jumped the ignition switch to rule that out, and briefly took out the coil resistor to check that... no change. spark plug cable installation / firing order has been confirmed, no issues. When spark plugs are removed they have a nice dry "tan" color which looks pretty good to me.
Checked the fuel system and gas flows from the carb drain plug without issue and all filters / strainers are clear. The carb was new when the engine was rebuilt... I have it apart now and soaking but all the components look very clean so i don't think that was the issue. Air cleaner has also been cleaned
I had already checked for carb / manifold leaks with a propane torch but did not note an improvement when propane was flowed around the flanges. Tried adjusting the idle mixture screw (currently 1 turn out) but no improvements
Compression dry is 115, 106, 116 and 118. Wet compression numbers went up a little bit (roughly 4 to 5 psi) indicating that the #2 cylinder probably does not have a valve issue, but is still weak compared to the others. Do not have any indication of a head gasket leak at this point. Also have checked valve clearances, intake and exhaust were in spec per the manual on all 4 cylinders
Any suggestions?? not a 8N tractor expert, so having a hard time figuring this out.
I have not removed the governor yet for inspection... but there is no "hunting" so I am not sure that is the problem either