Baffled, confused and covered in oil!!!!!!

[bikerboy]

This is a long story and it is in relation to my recently rebuilt A10 plunger frame. Not that it makes any difference but its got a large journal crank, thick flange barrels and an alloy head (A10 not A7)

I finished it a couple of months ago, regrind new shells, new bearing and bushes line bored etc etc guides valves all new the only thing not new was the pistons and rings they seemed ok and the bore measured ok, not great but ok.

Took it out done 28 miles and noticed a significant loss out of the engine breather once it got hot, I know some hate them but I fitted a wet sumping valve as it was wet sumping despite new check valve ball and spring. Unfortunately it also went on to one cylinder as something got dragged into the carb (no air filter as always)

Took the top end off again no big damage but as it was losing oil out of the breather decided on a rebore and new pistons as they were the only thing it could be. Flat top pistons not some 10:1 job.

Now the confusion starts. Started it no problem and oil circulated and pumped out of the breather at the same rate it came back to the tank. No smoke and it stopped after a few minutes so I assumed some oil had crept down to the sump despite the valve. Done 5 miles and everything cool, oil pumping round well and running fine so off I went, no sign of any more loss from the breather.

18 miles later most of the bike covered in oil and oil tank nearly empty. Was at a friends so topped up the oil and investigated. Circulating intermittently almost like a restriction in the line. Rocker feed even tho it was jubilee clipped blew the pipe off and oil pumping out at a rapid rate. Has to be a blockage in the oil tank I assumed. Tank off pipes cleaned even poked an old throttle cable down the tank from the top in case crap was in the tank return pipe. Nothing all perfectly clean and clear. Then fitted a replacement return pipe into a separate container so that I could watch the return easily.

Start it up again oil circulating nicely and again pumping out of the breather at the same rate that it is circulating. Assumed I must have broken a piston ring when fitting new pistons so compression test, all proved fine, still no sign of any smoke, spark plugs a perfect colour engine starts and runs fine.

After running for a few minutes, oil stops from breather and everything is perfect.

What the hell will cause oil to spew out at a ridiculous rate intermittently from the engine breather yet still circulate and run fine? Not only when its cold and has not been used even when it is hot and being ridden.

Pump has been tried and tested on my other A10 I only changed it to give me a tacho drive on my Super Rocket.

Oil straight 40 not that it matters.

Obviously all oilways checked and blown out during rebuild. I do not have one of the drain plug sumps with a magnet on it.

So no smoke at all, perfect starting and revving, plugs a perfect colour. I really am confused and baffled. I cant see why it would be the PRV which does have a new ball and spring anyway.

My next move is to remove the sump and leave a container under it to see if the sump is filling with oil but the tank level is not dropping, well not until it throws all the oil out of the breather its not. Anyway it cant wet sump when its being held at 50 mph for 10 miles surely?

Any suggestions would prove very well received

[lillygunny]

Are you sure the oil is coming out the breather hole?

[bikerboy]

Positive its pipe on this plunger of mine

[coater87]

 Just a thought, is the vent in your oil tank working?

 Blowing lines off, oil out of the breather, i can only think that pressure is building up and looking for an escape route.

 Lee

[duTch]

 

  Just a thought, is the vent in your oil tank working?

 Blowing lines off, oil out of the breather, i can only think that pressure is building up and looking for an escape route.

 Poking a wire up the tank vent would sort that, but taking the tank filler cap off and blowing in it will also give an indication.....or both in conjunction (saves any crap ending up in the tank)

[Klaus]

The breather is timed, are you shure the plug from the camshaftpinion is always in its hole?
Its only a suggestion, as you wrote, sometimes its all ok.

cheers Klaus

[Swarfcut]

Looks like too much oil added, and the scavenge side of the system with an intermittent fault. I would suspect an air leak or blockage in the sump pick up pipe...the welded 90 degree bend where it enters the crankcase behind the pump sometimes fractures, crack opens as motor warms up, pump sucks air instead of oil. The ball valve on the end of the pipe also needs a looky look....The ball movement on some pipes is almost zilch, restricted with a build up of carbon and other muck. The construction of this neglected component is detailed somewhere on the Forum.

 As a start, begin with the basics, tank, pipes, tank breather all clear, timed breather set up with no play, with a well sealing cork washer. With the inner cover off, check timing gears are correctly indexed and the correct ones.....Longstroke gears look the same, but timing marks slightly different, but unlikely on a motor which runs OK otherwise.  Oil pump... securing nuts tight, good gasket in place, no holes blocked, anti drain ball valve behind pump still in place. Check operation by pushing  a matchstick down the oilway and feel for a spring loaded ball.  Sump plate off, sump drained "dry", plate back on and oil tank filled with correct quantity of oil.  Start 'er up, oil should return as small gulps, changing to a good steady stream after a few moments running.  If the problem remains, the pick up pipe is number one suspect, followed by the pump. This all assumes the delivery side is working OK, but here an internal leak will overwhelm even a correctly working scavenge side.

 Look for a post "Oil suddenly coming out of the breather" what has happened is fairly common.

 Swarfy.

[muskrat]

G'day bb.
I'm thinking the scavenge pipe is the problem. As Swarfy mentioned the pipe can fracture or the ball restricts flow. The pump draws oil from the tank so oil is being deposited into the sump. The scavenge side of the pump is getting some but not all of it out till the level in the sump covers the fracture and starts scavenging normally. By this time oil is spewing out the breather.
Klaus has a good point about the timed breather. Double check it and the cork is a good size (10 to 20 thou crush).
As for blowing off the rocker feed.  clamp not tight. Do you have a filter on the return line after the rocker feed tee off but before the tank?
Cheers

[chaterlea25]

Hi,
Swarfy covered almost everything there
1 more , is there a magnetic drain plug in the sump plate? This can cause the ball to stick.
Also there's a pin or clip to prevent the ball being sucked up to the narrower part of the  tube, If missing the ball will block the oil

John

[RoyC]

Hi,
Swarfy covered almost everything there
1 more , is there a magnetic drain plug in the sump plate? This can cause the ball to stick.
Also there's a pin or clip to prevent the ball being sucked up to the narrower part of the  tube, If missing the ball will block the oil

John

"I do not have one of the drain plug sumps with a magnet on it."

He does NOT have a magnet in the sump,

[bikerboy]

Thanks for all your comments and help just to answer a few questions.

The cork washer on the end of the camshaft is fine and the breather peg is located.

It has no oil filter fitted, the return pipe has a simple T piece in that goes off to the rocker box just before it enters the tank. I think the rocker pipe blew off when I put my finger over the return hole hoping to encourage the oil to circulate.

I have, in my own mind,  put the problem purely down to the return system to the tank but I must admit it never occurred to me that the scavenge pipe could be cracked and if it is then that would explain everything. Sticky ball yes but I never thought about a crack.

With the plunger if my memory serves me rightly the scavenge pipe is actually bolted to the inside of the crankcase, I will have to hook out another set of cases and check. If it is then its an engine strip down for sure

Now correct me if I am wrong but if its not just the ball sticking, which I doubt I am quite thorough on a rebuild as a rule. That pipe returns directly to the back of the oil pump so removing the pump and putting an air line on it should expose a crack particularly if I wobble the pipe a bit as I blast air into it.

Looks like it could be another weekend spent on stripping and rebuilding again

[Swarfcut]

Yes, the pick up pipe is bolted to the crankcase at its lower end, bolt secured with a tab washer. BSA recommended never to disturb the pipe, as back in the day it was "cemented" into the crankcase, probably with the 1950's forerunner of Loctite Bearing Fit, which should do the job today. If it's loose and wobbles, not sealed to the crankcase, could be the problem. So, a finger over the oilway behind the pump and a plastic tube over the business end and a little bit of air pressure should locate a crack in the pipe, poor seal between pipe and crankcase or a dodgy bit of welding or brazing in the construction of the pick up pipe.  If all OK, check for a sticking ball...not moving enough, or the retainer in the ball housing compromised and drawing the ball up to block the pipe, as mentioned by Chaterlea John. If it all seems in order, then the mystery continues, so although it could mean a major strip, cross fingers for some sign of an answer.

 The design is different on S/A motors....a straight pick up pipe and internal oilways drilled in the alloy crankcase. Any chance one of the big end bolts on the big journal crank has caught and flattened the pipe, or even machined a hole in it?

 Swarfy.

[muskrat]

G'day Swarfy.
That's a good point. I didn't consider the LJ crank touching the pipe.
When I put a LJ crank into the A7SS cases I had to remove a bit off the nuts to give clearance as they hit the case. Also had to deepen the cam trough for the 357 cam.
Cheers

[KiwiGF]

Thanks for all your comments and help just to answer a few questions.

The cork washer on the end of the camshaft is fine and the breather peg is located.

It has no oil filter fitted, the return pipe has a simple T piece in that goes off to the rocker box just before it enters the tank. I think the rocker pipe blew off when I put my finger over the return hole hoping to encourage the oil to circulate.

I have, in my own mind,  put the problem purely down to the return system to the tank but I must admit it never occurred to me that the scavenge pipe could be cracked and if it is then that would explain everything. Sticky ball yes but I never thought about a crack.

With the plunger if my memory serves me rightly the scavenge pipe is actually bolted to the inside of the crankcase, I will have to hook out another set of cases and check. If it is then its an engine strip down for sure

Now correct me if I am wrong but if its not just the ball sticking, which I doubt I am quite thorough on a rebuild as a rule. That pipe returns directly to the back of the oil pump so removing the pump and putting an air line on it should expose a crack particularly if I wobble the pipe a bit as I blast air into it.

Looks like it could be another weekend spent on stripping and rebuilding again

I’ve heard of s/a bikes where the scavenge pipe had fallen off (or was missing) without causing symptoms of wet sumping, as the oil level just rises a bit to the level of the gallery in the case, I’m not sure if this is the case with the semi unit engines but I thought it worth mentioning, before you strip it down!

It does sound like the cases are filling with oil.

I had a puzzling oil supply issue with a Honda gb500 (no supply to head/cam), I eventually worked out what was going wrong by “experimenting” with pieces of tube and bottles to hold supply/return oil, this may be an option for you before you strip it down 

Edit...I just re read yr 1st post and oil was coming out of the head oil feed “fast” when you had the oil coming out the breather, no way it should ever be “fast” ....the oil supply to the valves on my bike is a dribble at best. That indicates the cause is probably a blockage (intermittent?) between the tee to the head and the hole in the tank pipe doesn’t it?

 I think Rocket Racer had this issue (during a rally) and the blockage was cleared quite easily.

[bikerboy]

Thanks for your ideas lads regarding the crank but I have run an LJ in plunger cases for years and feel sure I would have noticed anything like that but I will check it of course.