It is very unlikely that the oil pump will need attention in normal service provided that the oil is changed at reasonably frequent intervals as recommended. If however it is necessary to remove the pump the crankcase should be warmed to expand the aluminium housing in which the pump is fitted as the pump body is a very tight fit.
The four screws holding the plate at the bottom of the pump to the outside of the crankcase must be taken out, when the pump can be withdrawn. To dismantle the pump unscrew the small pump spindle gear which meshes with the worm gear on the crankshaft and which is screwed on to the pump spindle and is right-hand threaded. Take out the four screws holding the pump to the bottom plate when the cover can be removed and the gears taken out. Note : the oil pump has to be taken out before the intermediate gear can be taken off its spindle.