Boxerworks.com

Mine looked like these ones too. The spring was in pieces. edit: for accuracy

My big end bearings looked ok. (well not quite ok, but not wrecked) My broken bit of spring went straight to the rear main bearing.
The chamfer at the end of the slot in the main bearing allowed the 'approx' 3mm long piece of broken spring to be pulled into the crank/bearing running surface.
It would appear that these pieces of broken spring can end up anywhere.

Sorry 'bout the big piccys

Did we ever hear from twowheelsbetter (Darren from Tweed heads) how his rebuild went. He was getting Ray Peake to finish the job.

ME 109 wrote: The oil in the filter chamber will take the path of least resistance so it will open the bypass if/when the filter becomes blocked.
As I stated in earlier posts re the bypass, I can't see how a spring with seemingly light tension can resist 100 psi even with a brand new filter. Maybe it can at idle or low revs, but 100+ pounds??
I think oil is always bypassing the filter to some degree.

If oil passes through the filter at 100 psi, the bypass should be able to resist 100> psi.
My crude brain says the area of the hole in the retainer screw is 'maybe' 1/60th of a square inch.
Should the spring therefore be able to resist approx 6 pound pressure?

I thought the ball moved when pressure in the filter outer exceeded pressure in the main galley by "X," "X" being a figure that the engineers felt represented a clogged element or oil too cold or thick. VW T4 motors use a bypass that is conceptually similar (it's in the filter mount--not the cooler bypass in the case) and when removed/defeated in the interest of "filtering ALL the oil ATT" the filters must be bought carefully to ensure they have high enough burst resistance. I believe the relief's other purpose is to protect the filter during warmup.

So I'm seeing a day in the life of the bypass like so:

Cold motor start, the filter chamber pressurizes before the main galley, the bypass opens for a wee bit to equalize things and perhaps stays open while the cold oil is too thick to move through the filter fast enough to keep things equal between the filter and main galley.

Warm motor start, the filter chamber pressurizes before the main galley, the bypass opens for a wee second to equalize.

Filter full o' CRAP, not enough oil is moving through the filter to keep the pressure differential below "X," the bypass opens and stays open, sending unfiltered oil through.

The bit above in BOLD is the reason some VW folk remove/defeat the bypass, but in a cage application they can give up a couple pounds and some space for a remote high pressure filter like an Oberg or System 1 or Canton.

melville wrote:

ME 109 wrote: I thought the ball moved when pressure in the filter outer exceeded pressure in the main galley by "X," "X" being a figure that the engineers felt represented a clogged element or oil too cold or thick.

OF COURSE! Downstream of the ball it joins the galley fed with the filtered oil, so that would pretty much have to be the case. That completely explains why the spring pressure seems so light.

Thanks for clearing that up, melville.

Here is my theroy on the filter bypass system: Two things hold the ball on its seat against unfiltered oil pressure; the filtered oil pressure and the spring. The spring, which is a constant, represents the maximum allowable pressure drop through the filter before bypass starts. As soon as the pressure drop through the filter exceeds the spring pressure, the ball will unseat because now the unfiltered oli pressure exceeds the sum of the filtered oil pressure and the spring.

The filterd oil, and any oil that flows through the bypass end up in the same oil gallery immediately behind the oil filter cavity.
For oil in the gallery to hold the ball closed, wouldn't the oil pressure need to be greater in the gallery than in the filter chamber?
Most of you guys are expressing what I think.
But I'm missing something when it comes to oil pressure assisting in holding the ball closed.
Ooops, gotta go to work

Phew! for a minute there you had me thinking I used the wrong spring.
For my (1990GS) only the long one is listed.....#11 11 1 337 576
My replacement had the exact same amount of coils, only less compressed.
I'm pretty sure the short one has a different taper and less coils.

BTW -
Some models list both springs,
11mm #11 11 1 250 159
16mm #11 11 1 337 576.

and some models list both but with a cut-off date.

Fortunately their balls are both the same size.

As far as I can deduce, they all have the long spring after 02-85.
Before that , they could have either.

I think it is safe to assume that if the relief valve was jammed open, a lot of oil would not get filtered.
If it were jammed closed, you'd probably get leaks at the filter cover gasket or o-ring which I assume is the weakest link.
The metal canister that holds our filter appears to be a lot stronger than a typical tin can automotive oil filter housing.
On cars, if the relief valve is jammed closed, the oil filter will balloon up about 50% in size and start to piss oil out when a seam splits.
I've seen it happen.

As far as the specific pressures in different areas of the engine,
I'll leave that up to the elves that made it.
They must have a clue, the damned thing lasted 400,000kms.
I'm happy if my oil light never flickers and both sections of each valve cover have oil in them when I remove them.

Gee, my head hurts after reading this thread but as I'm looking for something today while it pisses rain today and oil changes on the R75 and zee GS will be de riguer today....sooze...me thinks I'll check my "balls" while at it. Not quite sure what I'll be checking for other than..."are they still there?"...."are they still strung up with spring tension"...so that's the plan...for now. I'll let you know what I find....now to find the barbie skeweres...hmmm.

PS: I'll be checking the cannister depth as well n the GS as the last time I checked at had recessed about 2mm over last 20,000 kms...another parinoa (?) of the airhead oil world thanks to some arcane article I read somewhere (probably I think was Oak article in Airhead mag a few years ago). I was suprised at the movement and that there would be any movement at all. Shimmed for the difference to achieve "proper" O ring pressure per the guru but I wonder if its worth the fuss....maybe though as its referred to as the "2000 O ring" nightmare!

You are exactly right Me 109, the filtered oil pressure is less the unfiltered oil pressure and without the spring, the ball would never seat and stop by-passing. Under normal conditions (filter not plugged) there is enough combined pressure of filtered oil and spring on the ball to keep it seated. When the filtered oil pressure is lowered by additional pressure drop through a dirty filter, the unfiltered pressure overcomes the spring and lower filtered oil pressure and the ball opens.