Author Topic: engine breather (again)  (Read 1886 times)

Offline Signboy

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engine breather (again)
« on: 07.11. 2016 07:40 »
Guys, still having problems with engine breather,  just cant get used to the amount of oil dripping from the breaher pipe, surely, it cant be right.  my bike is a 1953 plunger star twin, the engine breather faces forward just behind the primary chaincase , this ,when im motoring, distributes oil backwards all over the underside of the engine, then, when parked up, continues to drip into a small pool of oil about 2" in diameter ( not so much when on the main stand )
Some of the previous fixes suggest putting a tube from the breather and routing it through the back of the primary chaincase or to drip onto the chain.......my question is, would it be possible to "vent" the two inlet rocker covers to prevent the pressure building up in the first place ?
has anyone else done this ? did it work ?or will i wreck the motor by doing this ?
atb
Robin Watson

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Re: engine breather (again)
« Reply #1 on: 07.11. 2016 08:30 »
Hi Robin,

A huge amount of Oil coming out from the breather is not normal.

First be sure that is not causing in wett sumping. If the oillevel in the crankcase rise up by a longer stay the enginge spit off the oil over the breather. If the bike is in permanent use this willnot happend.

Standing on the sidestand can be also Gearbox oil, or the breathertube is running out.

Check your corkwasher behind the breather valve. If there is much play, also oil coming out, by not sealing the rotaion valve.
There had to be no play in axial direktion.

Befor you think about any other steps in direction ventilation over the rockerbox, please control that.


cheers Klaus


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Offline muskrat

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Re: engine breather (again)
« Reply #2 on: 07.11. 2016 08:48 »
I agree with Klaus. The cork seal should be thick enough to hold the cover off it's mate by about 1/2 mm. If the seal is good and the oil pump is scavenging properly there should be very little oil coming from the vent.
If the motor is wet sumping and your only riding around the block, the pump doesn't have time to clear the sump (can take up to 10 minutes). When running there is only a cupfull of oil in the motor.
Cheers
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Offline Signboy

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Re: engine breather (again)
« Reply #3 on: 07.11. 2016 20:38 »
Thanks for the prompt replies guys... got to say this leak is only after a good sustained run at speeds over 60mph !! i got the bike a year ago and have receipts from SRM who built the motor for the last owner in 1986 !   he only did 400 miles on it, stood in a garage till i bought it  ive done 1500 miles on it in 6 months !      might it be the little cork flappy thing has shrunk or something ??
anyhow, thanks again
Robin Watson

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Re: engine breather (again)
« Reply #4 on: 07.11. 2016 21:15 »
Hi Robin,

30 Years is a long time, and yes it can be the cork is shrunk, also the pistonrings can clued from oil by the long storage.
It seems the engine running hot over 60 miles, so have a look at the ignition timing,and  may be offset in timing. I have seen camrings with 6 degrees offset that meens 12 at the crank. Timing and control always  with a strope.

cheers Klaus


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Offline KeithJ

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Re: engine breather (again)
« Reply #5 on: 28.11. 2016 22:26 »
I have a similar problem.  I have just rebuilt my engine with roller main.  I have renewed mains, big ends, new pistons, rings, rebore, guides sleeved, etc.  Also checked the end float of the breather cork washer and it still drops too much oil out of the breather.  It does wet sump, had about two or three cupfulls after a couple weeks.  Any suggestions appreciated.
'59 A10RR + Second engine

Offline muskrat

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Re: engine breather (again)
« Reply #6 on: 29.11. 2016 09:56 »
It does wet sump, had about two or three cupfulls after a couple weeks.
G'day Keith.
You lucky bugga. My plunger does that in a couple of days! Only takes 5 minutes to drain the sump (with a sump plate and drain plug) and put it back in the tank. 20 years since the last bottom end freshen up so I'll put up with it till the next one and renew the ball and spring (the only thing not on your list of renewed items).
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
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Offline olev

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Re: engine breather (again)
« Reply #7 on: 29.11. 2016 10:59 »
Has anyone personally fixed the problem of oil coming out the breather by replacing the cork washer?
Shouldn't the centrifugal force on the cam wheel throw any oil away from the area?
and why did BSA leave a big hole in the breather valve that buts against the cork instead of sealing it?
are people sure this is where oil get into the breather?
just a thought,  cheers

Offline KeithJ

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Re: engine breather (again)
« Reply #8 on: 29.11. 2016 11:26 »
My main concern is the amount of oil coming out of the breather when the engine has been rebuilt.  Not sure what to look at?
I also don't understand why the cork washer appears to be so critical?  if there is no end float on that should be OK?  Back to basics if there is oil coming out of the breather that must be due to too much oil in the crank or too much pressure.  Too much oil means not scavenging enough and too much pressure mean it is not breathing properly.  Any other options?
Just thought, I have fitted an oil filter with a replaceable filter on the return side.  I have now done about 700 miles and it is due to be changed.  That could be it?  I will change the filter and see.  It's good to talk!
'59 A10RR + Second engine

Online bsa-bill

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Re: engine breather (again)
« Reply #9 on: 29.11. 2016 13:58 »
Quote
I have fitted an oil filter with a replaceable filter on the return side.

not all filters are suitable, you should be able to suck or blow through it without turning blue
All the best - Bill
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1959 Rocket Gold Flash - blinged and tarted up  would have seizure if taken to  Tesco

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Re: engine breather (again)
« Reply #10 on: 29.11. 2016 17:15 »
HI All,
my €0.02 worth  ;)
The cork washer needs to be compressed, If you can move the breather on its peg with your  fingers then its too loose! fine adjustment can be achieved by sanding the thicker cork washers to size
The hole in the breather top hat is for the drive peg and should not affect the breather

A newly rebuilt engine may not have achieved full ring sealing and some blowby will occur till the rings are fully bedded in

As the filter is on the return line it should not effect the oil circulation unless it has been connected back to front *eek*
the feed goes to the outside of the element, centre to oil tank

I do not like the idea of sleeving guides on aircooled engines ! I have seen too many fail *sad2*

John
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1963 RGS (ongoing)

Offline KeithJ

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Re: engine breather (again)
« Reply #11 on: 29.11. 2016 17:22 »
The cork washer needs to be compressed, If you can move the breather on its peg with your  fingers then its too loose!
I don't understand why?  Everyone says so but as long as there is no end float, why does it have to be compressed so much?

'59 A10RR + Second engine

Online RichardL

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Re: engine breather (again)
« Reply #12 on: 29.11. 2016 17:56 »
I think part of that must be so that it doesn't get thin-beyond-useful when the breather actually starts spinning.

Richard L.
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Offline KeithJ

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Re: engine breather (again)
« Reply #13 on: 29.11. 2016 18:16 »
It can still have end float without having lost the drive to the breather?
ATB
'59 A10RR + Second engine

Offline muskrat

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Re: engine breather (again)
« Reply #14 on: 29.11. 2016 19:06 »
G'day Keith and all.
When you offer up the inner cover the cork should hold the cover off the case by about 10 to 20 thou to sseal properly.
With 700 miles on the motor the rings should be well and truly bed in unless you were too gentle and glazed the bores. Blow by increases the crank pressure and with wet sumping there's too much oil in there so it tries to escape out the breather. Once the scavenge pump has caught up and you get bubbles from the return pipe the problem should disappear.
So drain the sump, wash the underside of the motor and go for a 50 mile ride and see if she still blows oil out the breather.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7