Oh sod!
it has just been brought to my attention, (thanks minicranks), that i cannot fit a star drive pump to my 998 without a 1/4 inch spacer.
however, having pulled a few old pumps apart, i have discovered that the drive "rod" is the same leingth on a 1300 star drive as the a+ drive 998 pump that came out of the motor, and these press out nice and easy.

Now,
can i get a new a-plus drive pump, and press the drive out, and replace it with a star drive one?
thus removing the need for a spacer
or is this a silly idea that will end up in a broken oil pump and an even more broken engine?

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speed costs....how fast do you want to go...

sounds like a spacer would be safer.... you're talking about spacing it away from the engine, right?

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did I tell you that I won a trophy?

yes, the oil pump area on the 1275 engine is shallower that the smallbore one, i.e the hole is bigger on the 998, and the pump is bigger.

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speed costs....how fast do you want to go...

we did that years ago with the `concentric' brand S pin drive pumps but the newer Minispares ones are not just keyed and press fitted, I think they are knurled on or something..

If buying new pumps you can use a slot drive one, and weld a slotted plug into the back of the star drive cam.
GR has done lots like this.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

ah ok, that answers it then it workes quite well on the old pump i tried it on
at last it proves im not insane

minor rethink required i think!
cheers

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speed costs....how fast do you want to go...