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farmall 300 fouling plugs

G

greg potts

Member
I recently rebuilt my engine, all is working fine, with the exception of fouling plugs,since the rebuild i have about 10hrs on engine.When i started engine up after rebuild noticed a good bit of black smoke at idle, even when you raise rpm black smoke was visible, then cleared up with higher rpm, tractor seems to run well at high rpms, only idle is black smoke noticable, also cant seem to get any heat in the engine, water temp never seems to move off of cold peg until you turn off engine then it moves slightly, was wondering what everybodys thoughts were?
 
Black smoke sounds to me like you are running rich, either the carb needs adjustment or the choke is stuck partway on or the air cleaner is blocked. Temp problem could be that you don't have a thermostat in the housing or just that you're not running hard/long enough to get it warmed up. With a thermostat my H and 300 will both warm up within 10 minutes or so putting around moving wagons or other light duty work. I had to put a temp gauge in the 300 because it didn't work.
Zach
 
Hey thanks for the info, black smoke still happens when air cleaner is disconnected, also checked choke it is wide open, thermostat is installed, engine gets warm you can touch block with hand and feel it is somewhat hot to the touch
 
On the bottom front of the carb (pointing forward) is a screw. Above that just below the flange are two screws. The left most screw at the top is idle speed. To the right is idle mixture. the lower screw is load mixture for full throttle.
I would adjust the top right screw out and in till it cleans up the smoke, and the left top till the idle is about 500 or so. If the right screw will not control the black smoke, the float level may be too high in the carb. If the adjustments work, the engine should go from idle to full speed when the throttle lever is quickly moved from idle to full throttle with no stumble (warmed up). If not open that bottom screw 1/2 turn at a time till it does. Jim
 
Checked choke its wide open, air cleaner is disconnected,checked plugs and found #1 to be wet and no fouling,2-3-4 heavy fouling, thermostat is installed, new gauge installed at rebuild, tested gauge with boiling water in pan and it went right to hot, so gauge is functioning
 
In my opinion never change two things at once. It just confuses the diagnosis. (which medicine cured the patient?) if the engine runs OK at High speed, the cap and wires are probably not responsible at this point. Extra fuel is. Jim
 
Yes They are so overcooled that it takes an hour on near full load to get the temp gauge in the middle.
If it gets above the middle something is plugged up (shaff in the fins), timing off, water pump not pumping well, or coolant low. They have a bypass that is too big and can be seen in the parts diagrams. Quite often the thermostat never opens. Jim
 
If you have a main jet adjustment screw like what B&S engines use you need to close that as that will lean the fuel mixture. Just close it 1/4 turns until it stops smoking. Hal
a88160.jpg
 
Many of the thermostat housings on those tractors are rusted so the coolant goes right on past the thermostat. Even when new there was not a positive seal as the tube slides up into the bored hole in housing. There is not enough material in there to install a seal on the gas engines but I have had it done on some diesel engines like 450 diesel. I have fashioned my own ideas on the old gas burners to ake the thermostat actually hole the coolant back. Also, like Jim says, bypass has a lot to do with them not warming up but all of mine do warm up even without the bypass restricted. Far as black smoke at idle, if the adjustments don't take care of it you most likely have wrong or damaged idle jet in carb. Had a guy bring a 300 carb into me last year that someone had been drilling things out and drilled the wrong jet for what he intended to happen.
 
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