I have an old, but worsening problem with my 445. The spec'd spark plug is an NGK BMR6A. Shortly after moving from about 300 ft. elevation to 4200 ft. I began replacing plugs every couple months due to carbon fouling. The local JD dealer suggested using a hotter plug. So, I purchased 2 NGK BMR4As. The "4" indicates a hotter plug. That fixed the problem for a few years, then the problem returned. So I installed the hottest plug available, NGK BMR2As. Again this fixed the problem for a few years, until this year. I am nonce again replacing plugs every couple months due to carbon fouling. I am concerned I may be doing damage to the engine.
The local dealer I had is gone and the new dealer refuses to offer any advice. He insists I bring it in for repairs with no estimate or "standard hours" cost. Sez they don't operate with standard hours cost and don't give out free advice. So, I gotta fixed it myself cause I can't afford an open pocketbook style of repair.
One suggestion made to me by a local owner is to remove the head and clean it. Plus install all new gaskets. He reasons oil, in addition to the normal crankcase bypass vapor, is getting into the cylinder causing carbon fouling, and the heads are probably badly fouled. He claims cleaning the heads and new gaskets fixed his father's 445 spark plug fouling. His theory is one of the gaskets was allowing crank oil to get into the cylinder.
So, I am about to order a set of gaskets ($145 on Ebay), remove the heads and replace any gasket I possibly can. Anyone have any other suggestions?
BTW, I have 1,300 hours on the JD 620A in this tractor and it does not burn any oil. I change the oil annually. Thanks for any and all comments and suggestions.