50 John Deere

GregV1

New User
Did valve job,new rings and bearings.Runs great in all gears until 6th then it blows black smoke and oil. Any ideas ?
 

Value guides? Coolant temperature? air/fuel mixture too rich? Actual bore diameter? New rings won't seal on an old bore that is worn egg shaped.
 
I assume when you say "black smoke and oil" you mean black smoke and black liquid. Does not mean it's oil and probably isn't. Wet black carbon will splat on hood and look like oil. If it is firing good then "oil" will be blue smoke. You say it's "black". Tells me you have too rich a mixture when the governor opens butterfly up as it will when taking off in 6th gear as it will use the load circuit a lot more than it will in the other gears. Start turning IN that fuel enrichment screw directly under the carb bowl and see if it doesn't clear up your problem.
 

Take the oil cup off the Air Cleaner and run it...

This by-passes the Air cleaner and Inlet pipe...a Blockage in the Inlet pipe can cause the enging to suck oil from the ventilator Pump into the intake and make the engine Smoke like the Devil when under a good load...

Mud-Dauber nests can and will drop into the "dog-leg" of the upper Inlet tube, blocking air flow to the carburetor..

Clean it out with a Garden hose up thru the center tube of the air-cleaner..ALL the way to the TOP of the Inlet tube ( Water running)..until the water runs Clean..

I would suspect this first...taking the oil cup off the air-cleaner will tell you if this is the problem,,,
Ron.
 

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