B is not running right.

So I rebuilt the carb on the B, got it started and it sounded and ran really well for about 15 min. Then all the sudden she sounded like a hit and miss engine with one cylinder actually hitting a fire stroke and the other cylinder popping white smoke out the air pipe. (I have the air cleaner and air stack off for cleaning, it was plugged up)

I am guessing one of the intake valves is not closing like it should allowing the bypass back through the carb and air stack. I also noticed once she died that the intake just past the carb was a frosted up a bit. It was mid 30s and had tried to snow so the air cold and wet.

Any ideas? I don't want to pull the head to check the valves, but if I have to I will. I did pull the carb back off and will check it out and change the plugs.

This is a new to me tractor, and my first antique one so excuse all the questions.
 
I would not tear anything apart until I could run it in Warm Air.. In the 30's when they frost up
they run like crap.
 
The big clue is the frost. RLA was right. When the temps are just above freezing and the carb frosts up, it will block some of the passages on the inside as well as the frost on the outside. Sometimes on my 40 and 420, I have to use the choke just to keep them running long enough to warm up. Especially bad when the temp is 30º to 40º and high humidity! You might want to check the plugs to see if one is fouled.
CPeter
 
Thanks everyone. The part store ordered plugs for me and will be in today. I did remove the valve cover and everything was moving as should and as far as I can tell the valves are closing all the way. My bore scope can see the valves move from the plug hole, but it's too big to get inside.

Weather is going to be crap all week here in WA so I will get some other things done. I drained the oil, that was NASTY! I need to find some cheap oil and do flush.
 
Did you order hotter plugs than what it originally called for? I go at least two heat ranges hotter in my tractors. Modern fuel is formulated to be atomized with an injector not a venturi. The finer mist of a fuel injector is easier to ignite. This is why standard heat range plugs wet foul.
 
Mag or distributor? I had a similar problem with my AR with distributor. Did everything possible to fix the problem; had recently replaced points, condenser rotor and cap. Put new plugs in. Checked air cleaner for obstructions. Finally at wits end, replaced points and condenser. Fixed the problem. The condenser was bad that hadn't run for more than an hour or two. This was on a tractor that had been starting and running excellent. Good Luck.
 
(quoted from post at 04:17:36 02/04/19) So I rebuilt the carb on the B, got it started and it sounded and ran really well for about 15 min. Then all the sudden she sounded like a hit and miss engine with one cylinder actually hitting a fire stroke and the other cylinder popping white smoke out the air pipe. (I have the air cleaner and air stack off for cleaning, it was plugged up)

I am guessing one of the intake valves is not closing like it should allowing the bypass back through the carb and air stack. I also noticed once she died that the intake just past the carb was a frosted up a bit. It was mid 30s and had tried to snow so the air cold and wet.

Any ideas? I don't want to pull the head to check the valves, but if I have to I will. I did pull the carb back off and will check it out and change the plugs.

This is a new to me tractor, and my first antique one so excuse all the questions.

" I don't want to pull the head to check the valves"

You don't have to take ANYTHING apart to verify that the valves are seating.

With the ignition "OFF" or mag grounded out or sparkplug wires off and grounded, crank engine by hand and you can "feel" each piston coming up on compression and if a valve is leaking you will hear it, as well as note that it leaks compression away as you slowly crank the engine.

The RH piston will be coming "up" on compression 180º of crank rotation after the LH piston, then there be 540º of crank rotation before the LH piston is again coming "up" on compression.
 
Autolite 388 is the hotter plug. The heat range chart shows 386 then 3116, and 388 being the hottest. 3116 is a non resistor plug but you could run 388 as well.
 
Thanks John, I appreciate it I will let you know how it goes once I get things put back together and fire it off again. I currently have the crank case cover off and soaking in about a gallon of diesel fuel,
there is about an inch and a half of sludge on the bottom. I am waiting on new plug wires, gaskets, and roll of oil tubing and fittings. I need to make a new oil pressure guage line the old one is leaking.
 

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