Author Topic: More wetsumping  (Read 5520 times)

Offline blackbikemike

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More wetsumping
« on: 18.11. 2009 17:08 »
I have avidly digested all the previous stuff on the forum about wet sumping, but here's my experience, open to suggestions please: Recently bought 1952 A10 plunger, which has been fairly thoroughly gone through: Reground crank, new standard bore, new pistons and rings, new valves, guides, springs. It was rebuilt over the past few years but hasn't been ridden for probably 20. I bought it knowing it had an ongoing problem, so when I first ran it I took out the drain plug (SRM), out came just under a pint of oil. Replaced drain plug, checked everything, it fired second kick, sounds lovely, oil returning strong into oiltank, after about 30-45 seconds starts smoking from both pipes  (quite a LOT of smoke) until engines splutters to a halt with oiled plugs. Undo drain plug, out comes another pint of oil. Remove sump plate, observe that oil is dribbling from scavenge pipe, poke up scavenge pipe....dribble stops. Left it for two days and the fresh tray had caught at the most a couple of tablespoons full. Replace sump, prime, kick, starts and runs clean for a minute or two then starts smoking again. Stop engine, remove drain plug, out comes another pint! So I haven't fixed it, but could it still be the scavenge pipe? Or the other non return valve? Or the pump? All suggestions gratefully received. I can't take it out for a decent run cos it's not road registered yet.
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Offline Desburnett

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Re: More wetsumping
« Reply #1 on: 18.11. 2009 17:53 »
Suggestions based on oil is entering cylinders and causing plug fouling. Providing head gasket is good oil can only enter past rings or guides. If pressure is building up inside crankcase this would force oil past rings so check the cork spacer / breather in the timing side and check the crankcase breather behind the cam shaft is free / open.
Check the breather in the oil tank is free / open. Finally check the condition and mounting of the oil pump. If its worn it will allow oil back into the sump and if its mounted incorrectly (without the fibre washer on the outpost) then other gremlins will set in.
Regards,
Des
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Online a101960

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Re: More wetsumping
« Reply #2 on: 18.11. 2009 21:16 »
Two things occur to me. Have you tried removing the sump plate and giving the ball a little tap? It may well be that the ball is not seating properly. The other thing that could be causing this problem is that the pressure relief valve setting might want checking. Again make sure the ball is seating properly and check the spring. If the pressure is to high the oil will be dumped into the sump and your crank assembly could be getting insufficient lubrication. If the sump is filling up then eventually the oil will find its way up past the pistons and be burned off. One final thought. Are the piston rings fitted upside down? that would allow oil to reach the combustion chamber. However given that your sump is filling up with the engine running I would suspect a problem with the pressure release valve. Try the anti syphon ball valve first as it is easy to get at and a little tap might just cure the problem. A10s and A7s are quite well known for the anti syphon valve  problem but this would normally be a problem when the engine is not running. In fact thinking about it if the scavenge side of the pump is being overwhelmed then I would strongly suspect the pressure relief valve, or a leaking pump.
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Offline blackbikemike

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Re: More wetsumping
« Reply #3 on: 19.11. 2009 09:09 »
Thanks very much guys for your prompt and clear responses. I have poked the anti syphon ball, but I didn't tap it, so will try that again first. After that I will work through your suggestions and hopefully sort it. Thanks again, I will keep you posted. 
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Offline Triton Thrasher

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Re: More wetsumping
« Reply #4 on: 19.11. 2009 09:54 »
I know little about BSA Twins but the oil pressure relief valve sounds doubtful as a cause of the cases filling with oil when running.  The scavenge pump is bigger than the feed pump, so if oil is building up during running, the scavenge system is not working.  Potential causes might be a gauze screen in the sump blocked with stray sealant; pickup pipe jammed against the bottom of the sump plate; vacuum leak between sump pickup and oil pump (test by sucking with the end blocked); scavenge side of oil pump somehow more knackered than the feed side;  flexible return hose restricted by kinking or internal collapse;   return pipe in oil tank too restricted, forcing too much oil to cylinder head; insufficient restriction of oil feed into cylinder head; no breather on oil tank.
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Offline blackbikemike

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Re: More wetsumping
« Reply #5 on: 19.11. 2009 13:35 »
Thanks TT. I've eliminated some: Gauze screen is brand new SRM and clean (washed it again just in case),Pickup pipe is well clear of plate,and the breather tube to tank is clear. I took the PRV off and gave it a tap just to be sure. So I will add to my list checking the vacuum, pump and hoses. I'm also going to try changing the rocker feed balance pipe from the race style ally one back to original and checking the banjo bolt holes, but I'm beginning to think it's going to be the pump one way or another.
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Offline rocket man

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Re: More wetsumping
« Reply #6 on: 19.11. 2009 20:00 »
another thing you could try put a rubber pipe on the pickup pipe put it in a container and
place it in a larger one under the sump so then you will know if its that
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Offline Rusty nuts

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Re: More wetsumping
« Reply #7 on: 19.11. 2009 21:22 »
The only scenario I can think of in which the plugs would oil so rapidly is chronic crankcase pressurisation.
You say you have good return to oil tank so that pretty much rules out pump. If it's leaking badly it's not going into the sump it will be filling yor timing cases.
PRV, I doubt it it. As I understand it, it dumps oil back into gallery next to pump & the only way into the sump is is up through the timed breather!

"Anti syphon ball valve" (assuming we are talking about the same thing i.e the cause of wet sumping) is not "easy to get at" on my longstroke, maybe later engines are different, only way to get at mine is by splitting cases & I had assumed same for later engines and anyway unless it's gone completely "walkabout" I can't see it being that. You'd have no oil in your tank to start with!
Assuming that the pistons actually have oil scraper rings fitted, I would clean plugs, run it till plugs oil up & remove rocker box inspection cover, there should be no more than a small amount of oil collecting where there rocker bolts run through the head, if more, pressurised oil is being pushed up & returning into head via valves you will see a flood.
 If that is the case it must be the timed breather/cork or the the crankcase breather pipe as pointed out by Des.
Unless the rocker oil feed banjo bolts are completely wrong (big holes) then you would get excess oil possibly passing past valves.
Hmm! You mention rocker feeds *idea* & there was a post recently!!!
http://www.a7a10.net/forum/index.php/topic,2001.msg12809.html#msg12809
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Offline Triton Thrasher

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Re: More wetsumping
« Reply #8 on: 20.11. 2009 08:00 »
The only scenario I can think of in which the plugs would oil so rapidly is chronic crankcase pressurisation.
You say you have good return to oil tank so that pretty much rules out pump.

But is it normal to drain a pint out of the sump after a run?  Why was that pint not pumped back to the tank?
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Offline Rusty nuts

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Re: More wetsumping
« Reply #9 on: 20.11. 2009 08:39 »
A pint seems quite a lot, after a run there's about half a pint in my sump.
Only get a pint after standing for several  weeks.
Suppose a blocked oil tank breather could prevent proper return, the tank pressurises as more oil is returned, to the point where the resistant pressure is greater than that applied by the pump. Maybe there is just too much oil, nowhere to go but up!
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Offline Triton Thrasher

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Re: More wetsumping
« Reply #10 on: 20.11. 2009 09:58 »
A pint seems quite a lot, after a run there's about half a pint in my sump.

If 1/2 a pint is normal, could the original poster be overestimating his 1/2 pint as "just under a pint?"
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Offline blackbikemike

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Re: More wetsumping
« Reply #11 on: 20.11. 2009 10:14 »
Could be overestimating, will repeat experiment and measure accurately, using the tube idea (nice one) to ascertain EXACTLY where it's coming from. Haven't got any time at the moment, but I'm certainly encouraged to have a list of "possibles" to mull over. I didn't know half a pint in thesump after a run was normal, so maybe I've haven't got a wetsumping problem, just a plug oiling problem.Thanks again for all your input. 
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Online groily

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Re: More wetsumping
« Reply #12 on: 20.11. 2009 11:28 »
The only time I ever had a motor which actually choked on oil pumped up to the piston crowns in those sorts of substantial quantities (beyond what can be burned off) was when someone had assembled it with the wrong rings.
The compression rings were too narrow for their grooves and were acting as mini-pumps as they moved in said grooves. The engine would start readily when clean, oil return would be normal as it wasn't a lube prob, then it would start to smoke, then die as the oil snuffed everything out. Small lakes of oil in there. With the head off, I could see it happen in front of my eyes by turning the motor on the kickstart. I was amazed. The reason obviously was the rings were not for the type of pistons actually installed. Changing them solved it immediately.
No idea if there's any chance of that as a possibility with this 'rebuilt' job, but if you decide the oil is returning properly and the levels are normal in tank, rockerbox and crankcase after all, and the breathing is OK . . . it has to be something fairly fundamental.
There are literally no limits to the horrors one can encounter in newly-acquired machines. Often, the horrors mount in a pretty direct relationship to shininess. I have yet to acquire a machine who's engine didn't need some degree of dismantling to make it proper. I live in hope, but not expectation.
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Re: More wetsumping
« Reply #13 on: 20.11. 2009 14:39 »
Hi All,
I would think even a half pint of oil is too much to drain off after a run
In normal operation the scavenge pump has twice the capacity of the pressure side so it should clear the excess in the sump, this is why when you start the engine after sitting for a while the return flow is constant until the sump clears!

I agree with groily's suggestions and observations,
""There are literally no limits to the horrors one can encounter in newly-acquired machines. Often, the horrors mount in a pretty direct relationship to shininess. I have yet to acquire a machine who's engine didn't need some degree of dismantling to make it proper. I live in hope, but not expectation.""

Another thing that can happen when an engine has sat for a long time is that the rings can seize to the pistons, this will give enough compression to start the engine but oil will soon travel up past the rings when running
HTH
John O R
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Online groily

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Re: More wetsumping
« Reply #14 on: 20.11. 2009 16:24 »
With you too John OR
Just one or two other such horrors . . . a running B31 (a current bike) with an Ariel piston up it (no oil control ring on that particular one) and a copper 'head gasket' thrown in for good measure because the deck height was also wrong; a VH Hunter which on starting up after a ' full rebuild' sent the big end cage straight back into the oil tank finely minced (quite pretty that); a twin of another marque with both pistons kissing the head, no oil retention device whatsoever on the drive side main shaft, and missing one camshaft end plug which had been replaced with . . . car body filler; another BSA with a similar jagged plastic metal plug in a 'repaired' crankcase after throwing a rod. Then there are mis-assembled gearboxes, the inevitable electrical spaghetti and all the rest of it. It's why, despite an optimistic nature generally, I don't live in expectation. Is also why I don't trust 'shiny'. Is also why I don't worry when getting anything 'new' to play with whether it works well or not - I assume it won't work for longer than the vendor's planned 5 minutes, so can't be disappointed. Unknown reasonably-priced quantities of these mature years simply have to be pulled substantially apart to be sure they're OK. And sometimes higher-cost better-known quantities with apparently excellent provenance have to be too . . . 
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