JD B problem

JCrutt · Dec 2, 2012

My 1950 JD B Poof"s out smoke by the clutch and blows valve cover gasket out at the same time. All vents have been removed and cleaned, it"s getting very annoying. Run"s great. Looking for idea"s. Ventilator pump issue?

Doug Sr. · Dec 2, 2012

You may have broke or stuck piston rings.
Doug

F-I-T · Dec 2, 2012

(quoted from post at 15:48:44 12/02/12) My 1950 JD B Poof"s out smoke by the clutch and blows valve cover gasket out at the same time. All vents have been removed and cleaned, it"s getting very annoying. Run"s great. Looking for idea"s. Ventilator pump issue?

Sorry, I got interrupted, so I'll edit my typos now...

Could be that the vent pump is not working properly, and that is allowing fuel vapors to collect in the crankcase, and a poof that is strong enough to blow the valve cover gasket out of position is actually an explosion.

Take the oil fill cap off and lay a playing card over the pipe. If it sucks down a bit, the pump is working. Keep your face away in case she poofs while you are testing.

Mark-Ia · Dec 2, 2012

Does it have gas in the oil?

JCrutt · Dec 2, 2012

I always shut gas off.
I will perform that check.
I do have a weak cylinder that leaks a little oil when I open peck cocks, and she does smoke lightly. But I have seen others like this and don"t have this problem.
It will do it even when I leave fill cap loose.
It runs so good is what has me stumped. I can win slow trator races every time. And even tho they are close in HP it gives my Brothern laws 50 a run for it"s money pulling. We take turns beating each other at tractor pull"s.
One of the gutiest B"s I have ever worked.

JCrutt · Dec 2, 2012

Ok thanks I will ck that. I wondered how to test it.

JCrutt · Dec 2, 2012

Doug, I considered that but the good power has lead me to put that idea on back burner for now.
Thanks for the imput. Basic mechanical tests and inspections show good. As diesel mechanic is why it has me stumped and I realy don't understand how the vent pump is supposed to work. I want to cover everything else before I do a tear down. I've never seen a 2cyl do this.

F-I-T · Dec 2, 2012

(quoted from post at 20:41:31 12/02/12) Doug, I considered that but the good power has lead me to put that idea on back burner for now.
Thanks for the imput. Basic mechanical tests and inspections show good. As diesel mechanic is why it has me stumped and I realy don't understand how the vent pump is supposed to work. I want to cover everything else before I do a tear down. I've never seen a 2cyl do this.

You ought to get a current hot compression check as well, in case the cylinder that is in not too good shape is really worse than you think.
The vent pump sits at the base of the fanshaft, governor end, and depending on the model year, is either a rotary vane or roller pump, so it pushes air into the crankcase anytime the engine is turning and the fan is spinning. Depending on the model year...and I'm guessing on your S/N, clean air is drawn from the air cleaner down the fanshaft tube, pumped into the governor, to the crankcase, and it crawls forward to the valve cover, where it is exhausted via pipe to the carb intake elbow to re-burn any nasty fumes. Later models had a separate inlet pipe.

Had an "A" one time the pump vane seized, as many do, and it would suck gobs of oil into the carb. Quick fix was to drill a small hole in the side of the fill pipe nipple until you could get around to pulling the fanshaft.

JD B problem

JCrutt

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Doug Sr.

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F-I-T

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Mark-Ia

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JCrutt

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JCrutt

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