Oil pressure gauge to the rescue again.

JimNH · Jul 7, 2020

Once again it detected a failed conical seal between the pump and timing cover. Oil pressure normally runs near 50 psi cruising except after a real hard run. It suddenly dropped to 15 or so with zero at idle. It happened before so I knew what to expect and even had a spare seal on the shelf.

Removed seal seems very soft while new out of the package is relatively hard. I wonder if there's a better one?

60 psi gauge is pegged at 2000 RPM on 20-50 oil when cold. I've been riding easy to warm up but considering 15-45 oil.

olympus · Jul 7, 2020

When you say seal gone soft, other that this observation is the seal split in any way?
The head of the seal sits in a machined out section of the cover, is it locating correctly?
Have you replaced the oil pump If so is the correct seal for the pump fitted?
Is the hollow dowel fitted into the pump which the seal sits over?
Gasket fitted to the pump??.... excessive clearance between the seal and cover.

sorry just thinking out loud

baz · Jul 7, 2020

What exactly happened to the seal? I've never seen one fail

kommando · Jul 7, 2020

Only failure of that seal I know of is if it drops before the outer case is fully home or its not shimmed correctly, as long its in place and the crush from the outer cover is correct then unless it dissolves its not going anywhere.

concours · Jul 7, 2020

JimNH said:
Once again it detected a failed conical seal between the pump and timing cover. Oil pressure normally runs near 50 psi cruising except after a real hard run. It suddenly dropped to 15 or so with zero at idle. It happened before so I knew what to expect and even had a spare seal on the shelf.

Removed seal seems very soft while new out of the package is relatively hard. I wonder if there's a better one?

60 psi gauge is pegged at 2000 RPM on 20-50 oil when cold. I've been riding easy to warm up but considering 15-45 oil.

Pics

JimNH · Jul 7, 2020

Bike engine is all original 11,000 mile. Seal fits correctly and appears to be correctly preloaded. Failure is a split. I haven't figured out how to attach an image but the split starts from the inside and progresses nearly to the edge. I suspect softening of the seal material and cold oil combine to push it beyond its strength. As I said, the gauge will peg hard with cold oil and even at a 45 mph chuise will be around 50. A hard run on a 90 degree day will still be over 40 so I have no idea how high it actually gets.

JimNH · Jul 7, 2020

olympus · Jul 7, 2020

does the hollow dowel protrude above the seal level?
Are you lubing the seal before offering you the timing cover?
Burs inside the timing cover damaging the seal?

olympus · Jul 7, 2020

JimNH said:

nothing attached...

maylar · Jul 7, 2020

olympus said:
nothing attached...

Umm... I see a picture of a cracked seal...

olympus · Jul 7, 2020

I'm sure I'll be corrected... that looks like the seal that's fitted for when the oil pump is replaced
The OE is a smaller one...or is it my eyes

Hortons Norton · Jul 7, 2020

Jim do you have a MKIII?

dynodave · Jul 7, 2020

JimNH said:
60 psi gauge is pegged at 2000 RPM on 20-50 oil when cold.

Surprised with the very low full scale gauge. I am now replacing my 150 psi full scale gauge with a 100psi full scale.
When 50w very cold (winter) it will peg the 150 FS if reved a bit. If the oil is very thick, the OPV escape passage will not flow enough to keep the pressure down.
I am now sure to change to 40w and not rev the engine until warmed a bit.
Some thing wrong with your MKIII seal rubber composition. They should not be that soft...
Refering to my combat not my MKIII

JimNH · Jul 7, 2020

Yes, MK III

I've owned the bike for over 30 years and this is the second seal failure. As it doesn't completely leave the scene there's still some pressure/oil delivered. The post is more for the reason to have a gauge. It's quite possible the two seals that failed over the years had been on a shelf for decades before I bought them. I'll source a spare from Andover to have on my shelf. Broken link removed

JimNH · Jul 7, 2020

Some thing wrong with your MKIII seal rubber composition. They should not be that soft...
Refering to my combat not my MKIII
[/QUOTE]
Agreed. Replacement was considerably harder so perhaps problem solved forever.

Onder · Jul 7, 2020

+1 on OP gauge.

click · Jul 7, 2020

Jim, what oil pressure gauge setup do you have? how is in plumbed in? keep 'thinking' about doing this on my MK3 but other things keep cropping up distracting me!!!

JimNH · Jul 7, 2020

click said:
Jim, what oil pressure gauge setup do you have? how is in plumbed in? keep 'thinking' about doing this on my MK3 but other things keep cropping up distracting me!!!

Nothing fancy here. I used a banjo fitting and a long banjo bolt and tapped it from the rocker feed line on the LH side, , so there's double banjos with one feeding a SS braided line to the gauge. It started to be a temporary fitting so simply Ty-wrapped to bars but it became permanent. Rockers were already fed by a SS line. I wish I could tell you part numbers, etc., but I did it many years ago.

baz · Jul 7, 2020

Lucky you had the gauge
Glad you caught it in time mate!

olympus · Jul 7, 2020

click said:
Jim, what oil pressure gauge setup do you have? how is in plumbed in? keep 'thinking' about doing this on my MK3 but other things keep cropping up distracting me!!!

I also had a gauge but no bracket or tubing....
Scrounged a piece of 3mm stainless for the bracket which is secured with a length of M8 studding through the hole in the centre of the steering shaft
purchased the stainless hose and fittings from Venhill & the 1/4 gauge fitting off flea bay
The feed for the hose is taken off the rocker feed port on the TIming case as I diddnt want to spoil the symmetry by connecting onto the cylinder head rocker ports

Oil pressure gauge to the rescue again.

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