Upper oil filter inlet flow orifice

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Floss
Cucciolo - the Lil Pup
Posts: 5
Joined: Fri Jun 18, 2004 3:16 pm

Upper oil filter inlet flow orifice

Post by Floss » Tue Aug 25, 2015 2:42 pm

Hello All
I've been off this site for a number of years (thanks to Steve's persistence and patience I'm back on) - ok, so I had a fling with Moto Guzzi, Velocette and Vincent (None registered on Ashley Madison fortunately) but they are all turning sour and I'm getting back to my first love - my '75 900SS.
In the meantime have been gathering new parts etc ready for a restoration.

One thing I've noticed is that there is a small aluminium slug with about a 2mm orifice fitted to the inlet of the upper oil filter chamber. I've check my spare 75 GT engine and a friends '79 900SS engine and neither of these have this flow restrictor fitted (inlet in approximately 7mm). I can't find this item in any parts manuals so I don't know if its a mod that has been done by a previous owner (I've had it since 1984) to get more oil flow to other parts of the engine by limiting the flow to the filter.

If you could shed any light/recommendations on why the orifice is fitted, it would be appreciated.

thanks

Floss

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 7:11 am

Re: Upper oil filter inlet flow orifice

Post by Ray O'Donohue » Wed Aug 26, 2015 4:50 am

This may be irrelevant or it may help: In racing and/or when using too heavy an oil,the front rocker box on bevels may flood,causing the front exhaust valve/guide/seal area to run submerged in oil. Not good. One solution is to restrict the oil flow a bit with such a plug. Another solution,perhaps safer in a low rpm (street) bike is to let the oil flow be unrestricted,but to provide an extra drain by running an external line down from a fitting tapped (pipe thread) into the exhaust valve cover.The line then is tapped into the oil filler plug.

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 7:11 am

Re: Upper oil filter inlet flow orifice

Post by Ray O'Donohue » Wed Aug 26, 2015 5:52 am

Also,if anyone is interested,I have one of those rigged up,with the upper end tapped into a welded bung on a valve cover and tapped into a filler plug.Braided steel line. Can send photo but only by e-mail (Posting a photo on this board is beyond me.) Will sell inc. freight for $50. U.S. only.

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 7:11 am

Re: Upper oil filter inlet flow orifice

Post by Ray O'Donohue » Wed Aug 26, 2015 8:43 am

I should add that the amount of oil which will by gravity flow down through this line is unknown,and the inner diameter of the braided steel line is not very large.Perhaps it is a big help,or perhaps not... I rigged the thing up for my race bike one winter,but never got back on the track to use it.

Floss
Cucciolo - the Lil Pup
Posts: 5
Joined: Fri Jun 18, 2004 3:16 pm

Re: Upper oil filter inlet flow orifice

Post by Floss » Thu Aug 27, 2015 6:22 pm

Hi Ray

thanks for your input, I believe you have a good modification for race applications. I'm still trying to find out if other stock engines were fitted with the oil flow into the filter housing restricted with slug drill out to approx 2 mm.

thanks again.

regards

Floss

Ray O'Donohue
Parallel Twin
Posts: 119
Joined: Tue Oct 13, 2009 7:11 am

Re: Upper oil filter inlet flow orifice

Post by Ray O'Donohue » Fri Aug 28, 2015 3:27 am

Right. I think this was not done by Ducati,but I may be wrong. The answer fill probably be found in the parts books.

wdietz186
888
Posts: 658
Joined: Sun Sep 10, 2006 4:40 pm

Re: Upper oil filter inlet flow orifice

Post by wdietz186 » Sat Aug 29, 2015 10:57 am

The 2mm [approx.] hole in the feed is standard from the factory. It is there to restrict the flow into the filter as it is close to the pump and if bigger it would reduce what little pressure and volume there is for the heads and crank. The heads and filter are fed off a pipe cast into the right side case that connects to the oil pump outlet. The filter is a partial flow arrangement [better than nothing,but not by much] and it dumps what has been filtered back into the cases.

Floss
Cucciolo - the Lil Pup
Posts: 5
Joined: Fri Jun 18, 2004 3:16 pm

Re: Upper oil filter inlet flow orifice

Post by Floss » Sun Aug 30, 2015 7:01 pm

Hi wdietz186

thanks for your input - your explanation makes sense to me but I'm still scratching my head about a couple of things.
1. Does this mean that all square case engines (except Millie) should be fitted with the restrictor or is the oil flow limited by another method in some of these engines. (Why do I have two engines 1975 and 1979 with no restrictor? Has the restrictors been lost?)
2. This does not appear in any parts books/ manuals I have found nor commented on by Faloon or Walker et al

regards

Bruce

wdietz186
888
Posts: 658
Joined: Sun Sep 10, 2006 4:40 pm

Re: Upper oil filter inlet flow orifice

Post by wdietz186 » Mon Aug 31, 2015 10:17 am

My 77 SS orig. cases have the plug with the hole, a set of 860 cases I replaced them with [Huge explosion!] have what looks like a steel cup plug driven in the hole, with a hole, and the set I replaced them with [just lots of cracks] also has the steel plug with a hole. So it looks like the factory used what was available. Take a close look at the hole and see if you have the cup plug in yours.

Floss
Cucciolo - the Lil Pup
Posts: 5
Joined: Fri Jun 18, 2004 3:16 pm

Re: Upper oil filter inlet flow orifice

Post by Floss » Wed Sep 02, 2015 12:15 pm

Hi wdietz186

thanks for your reply, I'll check mine out a bit closer.

regards

Floss

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