300 missing

400Dtractorman · Jan 31, 2016

I have a strong running 300 tractor. The problem i'm having is it fauls #2 and 3 plugs. Can anyone help with what it might be causing this. Motor doesn't use any oil and has few hours on a rebuild. Thanks Ed

Janicholson · Jan 31, 2016

If the head was rebuilt, were valve umbrella seals, or PC rubber seals installed? If not, were guides checked for clearance?
If you are running short lengths of time and light duty tasks, the plugs might be too cold. D21 (or equal recommended) can limit fouling. Were the piston rings gapped correctly, and the gaps staggered?
If it persists, a compression check (done by the book) is next. Jim

DeltaRed · Jan 31, 2016

Several reasons. Bad plug wires(should/must be WIRE,not silicone),Running too rich.Wrong plug, Valve problems... Pull the plugs,post a pic of them so we can see.

MARK ROBKE · Jan 31, 2016

My 300u did this once.Believe it or not,there was a blocked passage in the carb.It was running lean and was lacking power though.Took 2 tries to get the the carb passage cleared.Another thing,it will foul #2 or #3 plug if it idles a lot,or just does not get warmed up from frequent starts,and shut downs.I have not had a problem for a while,but if it misses it will be #2 or#3.Mark

f2355j · Jan 31, 2016

2 & 3 are going to be richer becuz they are the closest to the carb and 1&4 are further away. Try running a leaner mixture. Make sur there are no vacume leaks on intake manifold, specially 1&4

David G · Jan 31, 2016

You are correct, 2&3 will also get additional fuel due to the valve timing.

lucky2 · Jan 31, 2016

Might check your rocker arm clearance. I just read an article about a problem that sounds similar. Fresh rebuild and the head bolts didn't stay torqued properly then had to adjust valve clearance.

rhtx55 · Jan 31, 2016

Since the rebuild was recent. What color are the plugs black & sooty or black & soaked with oil?
Did you re-torque the head after initial warm up & cool down ? If not get it up running temp, ( run it high throttle for an hour) let it cool & re-torque the head, then reset the valves by bringing number one piston up to top dead center, set intake & exhaust on number one , then go in firing order sequence, bring the next cylinder up to top dead center, adjust it's valves, then go to the next.
Once you have all this done, put around a half a tank of good gas in it & let it run until the gas is gone. Do this twice more, this should have the rings almost broke in, if you can find a baker fan to belt up to, a dyno for the PTO, or a good 20 acre field to plow, that should finish "breaking" in the rings. Then it's time to change the oil. Should be good to go then.

300 missing

400Dtractorman

Member

Janicholson

Well-known Member

DeltaRed

Well-known Member

MARK ROBKE

Well-known Member

f2355j

Member

David G

Well-known Member

lucky2

Member

rhtx55

Member

Similar threads