860 ignition

I had to remove the tin and radiator this past week to have the radiator tank soldered and decided to finally replace some of the old ignition parts while I was at it. I replaced the old 216 plugs with 437's, new wires from TSC, and new distributor cap and rotor from BWD.

I fired her up and the engine is running much quieter now. Is it possible that I was getting incomplete combustion in the chamber before and a little gas was making it into the exhaust? It will after fire also if I do not idle it down far enough before shutting it off, but this happened routinely with the old parts as well.

I also removed the 437's to check them and all cylinders looked good except cylinder 4 was black and sooty. Based on my research this suggest incorrect air/fuel mixture or bad spark. Since the others are good I am guessing poor spark. Does this seem reasonable? I checked the spark on all four and it they are the same, yellowish/white that will jump 1/4". I think it could be improved based on my research here.

Thank you for helping someone relatively new to tractors and engines. I have read a lot, but do not have the hands on experience that all you regulars do.

run a compression check.. and set valves

check spark on that plug, swap it to another cyl and the other plug into that cyl. see if the dirty one cleans up and the other soots up.

lastly.. as someone else mentioned...a comp check won't hurt. dry then wet.

Incomplete combustion is a strange term that usually comes up when bs artist is selling a magic solid state ignition.

You are correct. Incomplete combustion is a bad description of it.

I took souNdguy's suggestion and swapped the plugs in cylinders 4 and 2. Ran the engine for a bit and checked the plugs. The new plug in cylinder 4 was not fouled. The fouled plug placed in cylinder 2 had a little bit of the ceramic cleaned up.

I checked the spark with that plug and was getting a white spark of about a 1/2". Cleaned the plug and put it back in cylinder 4. Mowed once around the yard and checked it again. Still clean.

I guess that plug did not have a good spark initially. Everything seems to be good now.

Thank you for the help.