Srm oil pump

[Steak-pudding]

Hi folks
My A10 plunger flash wet sumps if the bike hasn't been run for a few weeks, would a srm oil pump end this problem !

[limeyrob]

That is the 64000$ question

[mark]

Have 2 A10’s both with SRM oil pumps and neither wet sumps

[Rex]

I have one A7 with the standard BSA pump and that doesn't wet-sump (drain down) either.

[Steak-pudding]

Sounds like the srm pump dose do the job then !

[Colsbeeza]

I don't think that even SRM will guarantee that their pumps won't pass some oil. In the 1960s when they were ridden every day - no problem. We let them sit for too long these days. It isn't possible to make them with zero tolerances. Given infrequent riding, the main contributor nowdays is the anti-drain ball is not seating so that needs special attention for we Sunday riders (or in my case monthly rider lately). I spent days working on-and-off bedding in and testing the anti-drain ball to get it leak proof when I had the engine apart. Afterwards mine didn't leak with the old Mazak pump either but the pump was showing no oil pressure at hot idle, so I got the SRM pump and now get 15psig at hot idle. I can leave the bike for two months with zero wet-sumping. If you have to split the crankcase do it once and do it well. For my final test I used WD40 and let it sit for many hours until there was no leakage.
SRM did a write-up some time ago worth reading. They comment on "bypass" from pump Outlet to Inlet, and do accept a small bypass flow.
Until you can split the cases, a new pump should reduce wet-sumping to an acceptable level. A sump plate with a drain bolt is the next alternative and drain before rides. You will wreck the studs if taking the old sump plate off too often.
Col

[BagONails]

Was that oil pressure at idle improvement all (oil) down to the pump change Col or did you do the bottom end while you were at it?

Mine wet sumps slowly so I can leave it for two to three weeks and still not have to drain it down, anymore and it smokes a bit at start up, so I try to take it for a ride every couple of weeks minimum. (running Penrite 20W-60)

Now I'm paranoid about hot idle oil pressure ya bugger! How do I even measure oil pressure come to think about it, tap into the pressure relief area somewhere I guess, that's another search in the offing...

[Rex]

You don't want to start measuring or installing gauges etc as they're just more things to be concerned over.
They aren't termed "worry gauges" for nothing.

[muskrat]

G'day S-p.
My A7 plunger used to wet sump the whole tank in a few weeks  I slowed it down by removing the pump and used a squirt tube on a can of carb cleaner and pushed the ball valve open while giving it a good blast. I also stripped and cleaned the pump (make sure the gears go back in the same spot) and lapped the plate & nose as well as the base. It improved but still wet sumped, even useing 40/75 oil. Hence the FULL rebuild and SRM pump. Now not a trace of wet sumping even with two months of inactivity.
The A10 Cafe has end feed and roller conversion with the original 1957 pump (serviced) and doesn't wet sump at all. It has an oil pressure gauge with 20Lb at hot idle and 70Lb at revs. I didn't mod the OPRV but drilled the case to enter the passage up stream of it.
Cheers
ps: my rebuild https://www.a7a10.net/forum/index.php?topic=16831.0

[Colsbeeza]

Hi Bon, Yes I did the bottom end first and used the old pump. Unlike Musky I took no notice where each gear was installed, so fiddled around until they worked OK. I did reface the end cover to reduce bypass and was happy with its appearance. I had a pressure gauge fitted during rebuild many years ago and the original PRV, but with reconditioned bottom end it still gave me zero oil pressure hot. I was getting 60psig cold, but zero at hot (very hot) idle. Older and wiser heads than me say don't worry, as the centrifugal force created by the rotating crank will guarantee oil pressure at the big ends, providing some oil is bridging the T/S bush gap. Since Musky was getting good hot idle pressure, I thought I should have it too. So I decided to lash out for a SRM pump and PRV. I am fairly confident with that, but still check the return oil at the tank at each start.
Col

[BagONails]

I guess this confirms that at idle with hot thin oil the centrifugal (centripetal?) pumping at the big ends is beating what the poor little oil pump can deliver and pressure drops to naff all although there is still sufficient flow to maintain an oil film.  Reading Musky's rebuild blog again yes there was excessive end float, like mine about .008" but his journals, bush and shells were all in good order. To me this suggests having end float out of spec is not necessarily a death sentence (tho' not ideal) provided everything else is in good order and you do your maintenance.  If it starts getting worse though time to stop and strip it down!

Equally you could have good oil pressure, a good return, happily ride away and still blow up because the sludge trap is blocked!

Nerve wracking stuff particularly if you have a pressure gauge fitted, I can see why people don't fit them...

[limeyrob]

I fitted a oil pressure gauge to my A65 after the sludge trap blocked and it seized.  This is easy on a late A65 as they came with an oil pressure switch.  I had two reasons:
1 oil pressure at idle when hot would trip the switch so it was under 5psi and I wanted to see what it actually was and try different oil grades
2 I wanted some warning that the sludge trap was blocking so I would be looking for high pressure. In reality most of the time at revs it would be showing the 50 psi relief valve setting until it got hot then it would sit around 40 psi.  I'd fitted a return filter too so it was belt and braces.
It was better than the switch, these tended to fail but it still introduced a bit of flexy that could fail.  What it did do was show very clearly that a straight 40 or 50 was much better than a 20-50 when the engine was hot. This bike was tuned up a bit and ridden hard and it used to get very hot.  On one long fast run it boiled the oil!

[muskrat]

  On one long fast run it boiled the oil!

G'day Rob
that's about 250 C or higher. Wouldn't want the gonads to touch the tank
Cheers

[limeyrob]

Ha, yes it was OIF with the filler at the  front of the seat

[limeyrob]

If you can hear a munching sound it my humble pie being eaten: an SRM oil pump arrived in today's post....