OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk GV150 tuneup help needed

Here is the instruction page on installing the top bearing and oil seal:



Here is the instruction page on cleaning and checking the top bearing:



Oil seals work unless one of four faults exists:
Fault 1: The seal - especially its sealing lip - is damaged or the shaft has a non-round or rough surface.
Fault 2: The seal is eccentric to the shaft.
Fault 3: The shaft is too small relative to the seal.
Fault 4: The outer support ring of the seal does not fit the housing or the housing has not been cleaned properly, so leakage occurs between the two.

Expanding on Fault 1, the shaft needs a perfect, ground surface where it runs against the seal. If it is pitted, scarred, or otherwise damaged, sealing may be ineffective. Also, you cannot cure a rough shaft by reducing its diameter, since unless this is done on a lathe, you will always end up with the shaft eccentric to the seal. Even if you use a lathe, the seal can only tolerate a rather small clearance to the shaft - depending on seal type, it can be as little as 0.003" undersize from nominal shaft diameter. (Seals with springs around the lip may accept 0.020" undersize.)

Expanding on Fault 2, if there is wear in that upper ball race supporting the crankshaft, the shaft will wobble about. The maximum momentary eccentricity normal oil seals can stand, and still seal, ranges from only about 0.0015" TIR for low pressure types without springs, up to perhaps twice that for higher pressure types with springs. You deal with this issue by making sure there is no wear in that top ballrace.

Expanding on Fault 3, the sealing lip will usually create a wear groove in the shaft over a long period of running. A new seal will then not work effectively because the shaft is too small and the seal lip does not touch it properly. You deal with this by installing the new seal slightly higher or lower on the shaft so the lip does not coincide with the wear groove in the shaft.

Expanding on Fault 4, you need to be sure the housing is clean and undamaged before you press the seal into it.

Post-edit: I should have included Fault 5: Installing the seal backwards. Seals are usually uni-directional. If they have lips on both sides, normally one will be the oil seal and the other, just a dirt seal which will not hold under pressure.