Crankcase Scavenge hole strainer

olympus · Jul 22, 2018

Hi Guys
On early 750 cases there is no form of strainer over the oil pick up scavenge hole..... and as I have found, in my engine, debris has been sucked in destroying the oil pump driven scavenge gear.
Is there any modification available to fit a strainer?..
Looking at the current design & available space, I would think it to be a very tall order.... but if any one knows the enlightened on this forum will

Thank you

L.A.B. · Jul 22, 2018

olympus said:
On early 750 cases there is no form of strainer over the oil pick up scavenge hole....

It's actually the late 750 (200000+) cases ('72-73) that have no sump strainer.

xbacksideslider · Jul 25, 2018

Yikes! That's me/mine.

olympus · Jul 26, 2018

L.A.B. said:
It's actually the late 750 (200000+) cases ('72-73) that have no sump strainer.

I stand corrected... so is there no options for introducing a strainer?.

L.A.B. · Jul 26, 2018

olympus said:
so is there no options for introducing a strainer?

Not that I'm aware of. Adding a strainer to the '2' series crankcase oil scavenge pickup would, I think, be difficult, at least I can't recall anyone including a strainer as part of the scavenge modification. If there was such a mod. then I somebody would have mentioned it by now.
The 'dynodave' version of the scavenge mod. (where a number of small holes are drilled through the scraper flange instead of machining it away probably does prevent larger pieces of debris from being sucked into the pump.

Nortoniggy · Jul 27, 2018

I'd like to know what this "debris" is where it is coming from. Something must be wrong if there is something in the crankcase capable of damaging the oil pump

Ian

kommando · Jul 27, 2018

Nortoniggy said:
Something must be wrong if there is something in the crankcase capable of damaging the oil pump

And my Combat cases carry the scars of at least one blow-up, you can't stop the engine fast enough in most blowups and hence why the sump filter helps and at least stops the pump being added to the must replace list.

L.A.B. · Jul 27, 2018

Nortoniggy said:
I'd like to know what this "debris" is where it is coming from. Something must be wrong if there is something in the crankcase capable of damaging the oil pump

Obviously enough to make them reinstate the sump strainer on the 850.

batrider · Jul 27, 2018

Usually it is the tabs from the cam thrust washers used in those years breaking off. I had to replace my oil pump and fish metal pieces out of the pickup passageway. This was in the mid-80s.

Russ

olympus · Jul 27, 2018

Nortoniggy said:
I'd like to know what this "debris" is where it is coming from. Something must be wrong if there is something in the crankcase capable of damaging the oil pump

Ian

The lock wire on one of the tappet blocks was found broken away, this is what I assume got socked into the pump.Considering the tight tolerances between the components are the rotation speeds even a relatively small piece of debris could cause catastrophic failure

Crankcase Scavenge hole strainer

olympus

L.A.B.

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xbacksideslider

olympus

L.A.B.

Moderator

Nortoniggy

kommando

L.A.B.

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batrider

olympus

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