Britbike forum Forums British Motorcycle specific Brands Bsa bulletin board Just acquired a '71 A65 (restoration project)

If the oil tank isn't vented adequately, the result is wet-sumping. Oil will try to find any way out of the crankcase it can: the breather, the primary seal and any leaking gaskets. It'll start preferentially at the bottom...

Thanks..Mine just started at the base gasket and also ATF splattered on the top of the tank after a ride. Will start checking.

Good to know, I will check.

Lots to check. Thanks.

Hi Kurt
You said "There was a little ball of lint behind the OPRV, that's all I could see."

That could be your smoking gun, if the OPRV sticks all the oil "feed" will be diverted to the sump, and your pressure will vanish.
Best of luck

Thanks, Gavin, not sure what it was, maybe 1/8" across, soft, like cotton lint, resting in the cavity behind the OPRV. Guess I'll clean the valve and clean out all passages in the casting.

I checked the oil tank breather as Alex advised, it is clear, I was able to blow air freely through it from the end of the hose (routed out the end of the rear fender), however, in one place, I had wrapped it too tightly to the backbone, restricting it by maybe 40%.

That does not explain why the return pump did not pump the crankcase to the tank.
Take a good look, as mentioned earlier, at the return lines and the filter.
Does the filter return all the oil to the valve gear maybe, and nothing to the tank?

Thanks, Ger, I set up the oil filter so that it interrupts the main return line only, while the rocker feed follows the original path, direct from the oil union to the top end.

I had run the bike quite a bit in the garage with reliable return to the tank, and that first six-mile ride gave no problems, local roads, I hardly got out of second gear. Then "something" happened on the second ride after another ten miles more or less, with more sustained running through all four gears, at higher revs, usually around 3000 rpm, once I saw 4000 rpm briefly.

Can the filter block the return? What happens if you by pass it temporarily? Now... After the 2nd ride...
You must see oil return into the tank then.

Wasn't there a Britbike member who wrote a few months ago about the suction pipe
of the return pump which was loose or it dropped off or something like that...

It would have to be completely blocked to cause wetsumping. My Rickman uses about a .030" diameter hole in the cap and this is adequate.

Thanks to all for reading and following and thinking along with me, I appreciate your interest and advice.



OK, not the oil tank breather, then, cross that one off.



To be thorough, one thing I probably should have done on getting back home, would have been to re-start with proper amount of oil in the tank, engine sump drained, and check for oil return, with and without the in-line filter. I didn't do that before pulling off the sump plates, oil lines, oil union, right outer cover, exhaust.

All lines were quite tight, new hoses.

Now I'm thinking, keep going to the oil pump, almost there.

Always the decision awaits, put it back together and re-start and run, or embark on complete motor teardown.

[emoticon for pondering]

Just an additional thought..

Tempting to focus just on the return line to the tank, and that's probably where to look. But the scavenge pump (assuming it works and that, as Ger says, the feed tube is still there) pumps two lines in parallel. So I reckon what's important is the relative resistance of each route, and I think you need to look at both. If it becomes easier to pump to the head, either because the tank line is restricted or the head line somehow becomes 'freer', more oil will go that way and just circulate around the engine. A relatively small difference between the lines' backpressure can therefore significantly affect the flow back to the tank, even though pumped volume stays the same. All it takes is to reduce it to under pressure pump flow rate, and your engine will magically empty your tank.

So? The prime suspect is probably the filter line. But if you don't find much luck there, it would be worth checking the top end too. I remember, for instance, that there is a split pin affair up there that partially blocks the line so that the oil sprays nicely. If that fell out, you'd reduce the resistance to flow to the head a fair bit, which would, in turn, affect what flows to the tank.

And I'd be very tempted, as a first step, to go with Ger's suggestion of bypassing the filter to check it works OK without it. If nothing else, you'll eliminate pump and pump suction tube trouble.

Good luck!
Rick

Oh, sorry - just seen you've pulled it to bits. Disregard the last two lines...

Rick, that's a good thought, and things to check, thank you.

When I was mounting the filter, I asked here whether others had placed the filter only in the tank return line, or if they split the two feeds after the filter (and blocked the top end feed at the oil union). Answers came back both ways, one poster said he had tried it both ways on the same machine.

Interesting thought though about resistance, as people are using different types of filters on their bikes.

Do you have a sump plate with a magnetic drain plug?
I have had the same problem twice. Return side of pump not clearing sump and then an oil slick.
Both times the return looked normal when I left then five miles down the road oil everywhere.
My thinking is that the ball in the return pickup stuck. I had a sump plate with a center magnetic drain and no screen. I found one from SRM and they claim in the description the center magnetic drain can hold the ball down. SRM's is to the rear.
Also, no screen was probably not helping matters by letting more crud into the pipe.
Anyway, I got the SRM one and will report on how it works.
Besides the non return issue I also have the standard wet sumps when it sits problem. I probably need to pull the pump and replace the spring, as far as I know it is original. Any recommendations on where to buy a good quality spring? I have had some issues with pattern parts in the past.

Don't want to keep jumping in. But I also have a Wassel sump plate with magnetic plug. But the plug is in the front. Running a screen though.

Gary, no problem, jump in, more information the better, I'm learning.

htown, I have not checked the ball in the pick up pipe in the motor sump yet. I do run the stock sump plate with a drain added (not magnetic), and the screen is in place.

I've gotten this far with a bike I don't know the history of, so I will keep on at least to the pump. When I have the pump in hand, no doubt I'll be looking for some parts, at least the ball and spring (gasket, etc.).

My sump drain:

Kurt, Same with me as far as the bikes lineage is concerned. No idea who worked on it before. T-bolt bottom end, Lightning head. Part of the fun I guess.

Just out of curiosity . is the drain bolt directly under the oil pick up tube ?
It looks to be a bit long and may be blocking off the return pick up tube.

Thanks for your concern. Here's a pic of the inside of the sump plate with the bolt installed. I had Classic Fabrications TIG weld a flange nut on the outside of the plate, then used a flange bolt, drilled for lock wire, as the drain bolt. The bolt is off-center and installed opposite the pick-up pipe. I have since replaced the brass washer with a fiber one. Also, I checked the ball in the end of the scavenge pipe, and blasted it clean with WD-40.

Rainy day, so I'm in the garage this morning, I removed the inner right cover to expose the oil pump. I gather I need to remove the crank nut and worm to remove the pump.

By the look of things, the cover has never been off before, screw heads in good condition, AAU reluctant to come off. There's some red clay-like sludge in the gearbox oil residue at the low point, a magnet picked up a few hairs. Notice the burr raised by the lockwasher under the uppermost nut on the gearbox door, just sitting there since July 1971. Also, of the three oil pump mounting studs/nuts, the forward one, the plain-nutted one, had a plain washer under the nut, not a tab washer (76-0138) as shown in the parts diagram





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If you can remove the oil pump studs it will make life a lot easier. The pump will just drop downward.

Piece of cake. Remember the nut is left-hand thread as is the worm drive(it unscrews just like the nut).

Thanks, Allan, Alex. I had read that about the LH thread on the end of the crank, but thought I'd post up and see who reminds me of it, or tells me of exceptions. Removing the nut and worm gear went easily enough. The tab washer wasn't really folded over, just sort of mashed flat, but has done its job for 43 years. I decided not to pull out the studs, didn't want to risk stretching the threads by double-nutting.

The three nuts holding the pump on were tight, the gasket intact, but not 100% aligned with the holes. The ball seat doesn't look too great magnified, looks like some corrosion, maybe some scoring, maybe some original machining marks. Will pull the pump apart next, then collect some new parts.

How long is a new spring for the check valve? The one that came out is just under 7/8".

Kurt, Had a chance to look at mine today. I removed OPRV and found the same cotton lint you described in mine. Wonder if the same person assembled both engines ? Going to do the same cleaning as you did.

Those nasty little pieces of shop rag can be real destructive in the wrong place, I use paper towels for the last clean before assembly.
It's nice to see you doing right by this old bike.