next question - huge oil leak, sometimes...

Started by paul.w, December 10, 2020, 04:52:18 PM

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paul.w


singleminded

Paul, a magneto sprocket puller is available from the club..i made my own, but i do have a lathe.

singleminded

That's interresting about the pump not scavenging. The pump is driven by the inlet cam and there should be a swashplate between the slotted nut and the pump shaft. The feed side has direct drive from the pump shaft but on the scavenge side the bottom gear is keyed to the drive spindle, the driven gears just freewheel on their pivots.
I have heard of one other source of sumping. The return pipe which rises near to the top of the oil tank, or at least it should, was cracked  near the bottom. This allowed the oil to pass through the crack and drain into the sump, an odd one perhaps but it can happen..John

Thomas

#7
I am not familiar with the oil pump of a 1930 model but it sounds as if it doesn't work. Start the motor again and check if oil returns into the tank.

In my case I need to dismantle the sprockets to reach the pump and I made a tool in my shed.
1946 BSA C11
1937 Sunbeam Model 9
... and a scratched Hyundai
(MSCR member)

paul.w

well, thats interesting.
I've got the cover off the timing chest.  However, to remove the magneto sprocket it appears I need a 9/16 cycle thread bolt - as the inside of the sprocket is threaded and I'm guessing it uses a bolt to push it off.  Am I right??   As i don't have such a bolt and it isn't possible to get a puller on it any other suggestions?

Also...  I removed the oil return pipe  - and a huge amount of oil came out of the crankcase.  Over two pints!  Its not from the oil tank as there is a tap and its off - so this oil that has accumulated in the crankcase.  That says to me that the scavenge pump isn't working properly.  I'm wondering that, if there is that much oil in the sump, it is getting past the bushes as the oil level might be higher than the bush.  It may be that if the pump is at fault I may not have to remove the sprockets - but I'd still like to have a look.

paul.w

#5
That explains the difference, mine is 1930.  I think it is fairly obvious something is amiss inside the timing chest.  I wonder if the lower sprocket has come adrift (the top one appears to be secure).  That may also affect the timing which I think might be the case - that would also explain why it kicked back when I tried to start it with the adv/ret lever set to its normal position.  I shall investigate tomorrow.  Thanks for your advice.

Thomas

The year is important, Paul, because the design changed almost from year to year. Mine is 1937 and when dealing with an inspection hole, your model must be an earlier one. The chain is loose? Check the sprockets. If it is the lower one then dig deeper and check the rocker arm bush. Such an oilflow is not good and I don't believe it is wet sumping at all. 
1946 BSA C11
1937 Sunbeam Model 9
... and a scratched Hyundai
(MSCR member)

paul.w

Thanks for that Thomas,
i am struggling to reconcile those photos to the timing chest on my bike - it does look to me to be quite a bit different.  What year is that and did they change the design? I'll take the timing chest cover off next- the chain is incredibly loose as well so there is something amiss in there I think.  I'm wondering if a sprocket hasn't come loose or something.  Maybe when its off the pictures will make more sense.

The timing of when it leaks badly is odd, as i described i did a few miles and got a flood - another 10 and no leak at all and then another flood after the 10 miles home.  When I fired it up earlier this evening it was like the Niagara Falls for a while and eventually stopped - presumably when it had emptied the content of the chaincase.  So i then left it for a couple of hours and tried again, and again got vast amounts of oil - which is really weird 'cos it suggests the oil got in there while it was standing in the shed (I have a tap in the oil line so it can't be wet-sumping when its standing).  If I remove the inspection cover the timing chain is throwing huge amounts of oil about - I'm sure far more then should be there. Next task has to be to remove cover and look inside.  At least with Covid there isn't much else to do and i can't really ride it.

Thomas

Hi Paul,

I don't have a sleeve between the timing chest and mag and I don't believe there should be one. If oil sometimes leaks and sometimes not, I would check the time and/or milage intervals. Maybe oil has simply time/miles to collect somwhere and drains into the chain case. Oil in the timing chain case can only come from the timing chest via the inlet cam shaft bush and the rocker arm bush. Attached are inside and outside pictures of the cover. Did you check the bushes?

Cheers, Thomas
1946 BSA C11
1937 Sunbeam Model 9
... and a scratched Hyundai
(MSCR member)

paul.w

#1
I will get this bike to behave - but just not yet! 
Model 9.
Now I've sorted (mostly) the carburation, my next problem is a colossal oil leak. Its coming out of the magneto drive shaft on the rear of the timing chest.  Strangely, not always.  I stopped this afternoon when it died (another problem, to be addressed later) and it dumped a pool of oil about 6 inches in diameter in the road.  I then did another 10 miles and stopped and it didn't leak at all. Came home, parked it in shed and no oil leak.  went out a few minutes ago and started it - and immediately another oil slick of Torrey Canyon size.

I  removed the inspection plate to see the timing chain flinging huge amounts of oil about.  I suspect the timing chest is getting over-full (but only sometimes, which I can't explain) and it is then getting thrown out of the mag drive hole.  I have a mate with a Model 9, and he says he made up a collar glued between the timing chest and mag. to stop oil getting out.

My question is.....  is the oil getting to the timing chest excessive, or is there an oil seal (felt?) on the end of the crank behind the timing gear that should stop oil getting into the timing chest which is past its best.   Or -s the scavenge pump weak/worn?  Secondly, has anyone else (other than my mate) fitted a sleeve between the timing chest and mag to stop it?  The mag may be coming off soon anyway (the next issue) which would give me an opportunity to do this.