Wet sumping

Generally it is the drive side of the oil pump that gives the most problems. The reason being that this is the scavenge and return to oil tank side so consequently wears the most due to sucking up and grinding any rubbish dropped in the sump. It also runs on air quite a lot, firstly on start-up and then once it has cleared the oil from the crankcase.

So check the end plate, on that side, as well as the shaft clearance, gear teeth and gear housing. Any serious grooves or chipping will give problems. The mating face for the pump body does distort with aging and over-tightening of the pump mounting nuts. Always fit a paper gasket and put a scraping of sealant between the pump face and the gasket.

There are several good articles, about these oil pumps, within this website. Check out The Tech section Heavy Twins â Oil Pump Servicing. Use the Search box above and top left for more useful hints from owners. Dommie oil pumps are still easy and cheap to find at A/Js, in OBM Ads and eBay.

Previously phil_hannam wrote:

Generally it is the drive side of the oil pump that gives the most problems.

What is meant by the "drive side"? There is a top set of gears, a bottom set, the left side is the gasket face and the right side has the outlet to timing cover.

On dry sump engines the drive gear are the thinner ones, the scavange are normally double the thickness of the drive gears to remove the wet sumping and keep the sump clear, they also have to cope with air from the piston blowby when the breathing can't cope.

Norton follow this rule so just look at the gears.

My mistake for not being clear with the description. The set of gears and associated chunks, that need a close inspection, are the scavenge gears which are nearest to the driven end of the pump. See attachment.

Attachments
oil-pump-scavenge-gears-bmp

Previously john_holmes wrote:

On dry sump engines the drive gear are the thinner ones,double the thickness of the drive gears to remove the wet sumping

I have a few pumps apart and the driveshaft drives both a thick gear and a thin gear.

Phil Hannam is referring to the gears closest to the drive pinion as he explains in the next post. These are the thick gears. One scavenge gear is fixed to the shaft (I have never removed one). One thin gear is keyed to that same shaft. One thin gear drives another thin gear only but not the rest of the pump.

There is no gear of any thickness that can remove wet sumping overnight.