Lightweight oil pump differences?

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clanger9
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Lightweight oil pump differences?

Post by clanger9 »

Does anyone know what the differences are between Lightweight oil pumps? Roy Bacon's book has some nice photos of the various Heavyweight pumps, but nothing relating to the Lightweight.

The reason I ask is that I've been sent the pump at the top of the photo below as part number "042104", but 1) it's got an extra oil hole near the slot, whereas my CSR one doesn't and 2) it's not stamped "G2" on the end, whereas my CSR one is.
IMG_1835.jpg
IMG_1838.jpg
As first I thought it was a Heavyweight pump, but the oil hole position doesn't match any of those in Roy Bacon's book. Can anyone shed any light as to whether it really is part number 042104?

Finally, I am aware that the CSR pump is higher capacity than the standard Lightweight pump. I just hadn't realised how much: the plunger stroke is increased to 4.48mm (from 3.24mm, according to my measurements). It doesn't sound a lot, but that equates to a massive 38% increase in displacement! Sadly, I don't think the high-capacity CSR pump was ever made available as a spare part.

Fortunately, I've managed to source a "good" CSR pump (the other one in the photo), so that one will definitely be going in the new engine...
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1989 Moto Morini Dart 350
1993 Ducati 750SS
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Ozmadman
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Re: Lightweight oil pump differences?

Post by Ozmadman »

Must admit Paul I wasn't aware of any difference as my pump was fine in my Model 8 and I don't have a picture of that unfortunately. You can easily see from the pictures the difference in pump "throw" and I reckon the unmarked pump is the one used as a replacement for everything, hence being unmarked whereas the "G2" pump is the original one that was fitted and the one I would use too. What was your original pump like then??
Paul
1960 Model 8
1974 Yamaha RD250B US Model 6 speed
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clanger9
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Joined: Sat Jun 20, 2015 9:38 am
Location: Chester, UK

Re: Lightweight oil pump differences?

Post by clanger9 »

My original pump was unmarked on the plunger, but the gear teeth were worn dangerously thin. Possibly just general wear and tear, maybe made worse by the fact that my crank has been hopping about on worn bearings...
IMG_1709.jpg
The worn one is at the front of this photo.
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1989 Moto Morini Dart 350
1993 Ducati 750SS
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