The oil pump on my DT1C has been leaking since I got the bike, but of late, it's been leaving puddles of "my injector oil of choice." Mind you it works just fine, just is puking oil past the seal next to the plastic wheel.

Ordered a rebuild kit from hvccycle.net. Upon removing the cap, you can imagine my surprise when I saw this!!

More teeth missing than a banjo player at a hootnanny...

Gosh. Says a lot for premixing.

Pretty hard to kill an oil pump but you got close. Probably got your money's worth from it.

On the positive side , there are still replacement worm wheel gears about .

Since most folks believe the pumps are interchangeable and give no thought to the ring gear/worm gear compatibility requirement, it is not surprising to see the damage. The damage didn't occur because the teeth failed in normal use. The worm gear pitch was different so it ate up the ring.



Of course, that's just my opinion.

I have an oil pump in good shape from a DT1C I am parting out if you are interested. Text 480 797-7716. Sean.

In this bikes case I have no history before last spring. Pump was on, but appeared not to have been used for some time, since the oil tank window was gone, pump discharge hose was disconnected and a bolt in the cylinder inlet port. Oil pump looks original, clutch cover looks undisturbed, but, who knows?
I was thinking this was damage that may have happened when I first fired the bike up on pre-mix, the base of the shaft where the plastic gear resides was pretty corroded, so thinking maybe the pump shaft was resistant to turn and/or seized at initial start up? I plumbed the oil pump shortly after getting the bike running, and pump was leaking a little past the seal by the plastic wheel right away, and only worsened over the past few weeks. Pump worked as soon as I plumbed it, and I've put about 1000 miles on the bike up to opening the pump up and finding the damaged gear.
Anyway, thanks to Midlife I have some DT1C pump parts headed my way. THANK YOU!
I will be pulling oil pumps prior to engine fire up with future resurrections, just in case.

Another possible failure scenario would be that the internal cylinder stopped spinning freely and the worm gear ate the ring gear.
That can happen from rust or debris inside.