Oil pump gear

[Sam]

Hi a wee question, in the box of bits I received with the 250 scrambler there were two oil pump gears one was palstic/nylon and the other metal are there any benefits from either? also there were two dots on the gears what are both marks for?

Cheers

Sam

[Rick]

I've never seen one on a Ducati, but many manufacturers used laminated phenolic resin/cloth gears, sometimes called fiber gears- use the steel gear.
The dots are there to synchronize the crankshaft position and the ignition spark. The oil pump gear acts as an idler between the crankshaft gear and the contact breaker camshaft- when synchronized, one dots aligns with a dot on the crankshaft gear and the other aligns with a dot on the contact breaker camshaft gear.
Rick

[Jon Pegler]

The plastic oil pump gears were produced by Mototrans for the engines they built in Spain.
They were quite notorious in their day for stripping teeth, causing the motor to stop immediately, due to all drive to the points drive gear going.
I've got a box of those gears myself, but I will never use them.
They've even started making reproduction ones in Spain, presumably because there are so many stripped gears over there.
As Rick says, use the steel gear.

Jon

[Sam]

Thanks for that info, I'll use the steel one. However there is no dot on the crankshaft gear, should it be on the tooth at the keyway ? There is also a larger chamfer on one of the teeth on the crankshaft gear.

Sam

[Rick]

The dot on the gear is essential to setting the ignition timing, if you call the keyseat for the woodruff key 12:00 o'clock, the dot is at around 5:00 o'clock.

crankshaft timing mark.jpg

Rick

[Sam]

Hi Rick,

Thank you,could you please count the number of teeth from the key seat please.
The steel idler gear I had is past use so on the look out for another I have located an alloy set may go for them. p.s. there are no dots on any teeth on the crank I have.

Sam

[Ian B]

could you please count the number of teeth from the key seat please. Sam

I've just had a look at 2 250 cranks I have and they are slightly different. One has the keyway directly in line with a tooth and the other has it in between the teeth. If you count the tooth inline with or to the right of the keyway as number 1, then the dots on mine are at tooth 7.

The steel idler gear I had is past use so on the look out for another I have located an alloy set may go for them. p.s. there are no dits on any teeth on the crank I have.
Sam

I've a spare oil pump drive gear, if you need one drop me a pm.

Cheers
Ian

[Sam]

Hi Ian,

pm sent

Sam

[Rick]

I looked at several crankshafts also, mine were more consistent than Ian's- they all look like these drawings.

timing side 2.jpg

timing side closeup.jpg

The keyseat is in the valley between teeth- the line through the connecting rod is inline with the keyseat.

Rick

[Sam]

Cheers Ian idler gear arrived this morning.

Thank you!