engine breathing

[baz]

after reading about excellent results on norton commandos with a reed valve built into the sump plug i thought i might try it on my A10
on the commando the reed valve feeds straight from the sump to the oil tank
the biggest advantage being reducing crankcase pressure eliminating oil leaks and the over big advantage is any wet sumping is returned to the oil tank in the first few kicks
can anyone see why this system wouldnt work on an A10?
cheers

[Triton Thrasher]

Prior reading:

https://www.accessnorton.com/NortonCommando/bsa-a10-additional-breather.30032/

[baz]

oh for christ sake that was my post!! i didnt think it had been replied to!
cheers

[muskrat]

G'day baz.
I have Bunn breathers (no longer available) on my cafe. The outlet runs from the normal hole in the LH case to the oil tank and the vent for it has the breather.
For the system to work best you need an inlet as well. A very light reed valve both ends. In through the rockerbox out via the normal breather. I modified the timed tophat breather to be "un-timed" so open all the time and breathing controlled by the Bunns.
Cheers

[baz]

hmmm i hadnt thought of an inlet,the main reason for trying this is the bike gets infrequent use and i dont want an oil tap or a mag cut out oil tap etc etc
if it helps stop oil leaks along the way even better,i do believe in using my bikes for what they were designed for and i do thrash the bike
my moto is if it breaks its my fault and i'll build it better next time
cheers

[BSA_54A10]

A very simple way t fix this is to fit a magnetic drain bolt to the sump.
Pull it out and pop it on the fuel tank or oil tank cap

[baz]

A very simple way t fix this is to fit a magnetic drain bolt to the sump.
Pull it out and pop it on the fuel tank or oil tank cap

ive had a drain bolt in my sump plate for over 30 years but i cant access it any more without the bike being on my ramp
cheers

[baz]

i have taken a pipe from the sump plate to the inline reed valve which is positioned just behind the gearbox then the pipe goes to the original breather tower
i have fitted an additional breather on top of the existing one ,this is tee'd off to the original rotary timed breather pipe from the engine and then vented to the back of the bike
so far its working perfectly
theres only a very small amount of air that comes out of the reed valve and thats at tickover speed i have been out on it  today ,held it at 80mph for a short spell and all is well
but to be honest all was well before apart from a rocker box base gasket leak and a leak from the rocker oil feed banjo now fixed
so time will tell if this helps at all with oil leaks?
also if/when it wet sumps it should pump any excess oil straight back into the oil tank instead of out the back off the bike from the original engine breather with any luck
i'm very pleased with it so far
cheers

[Slymo]

Surely if the timed breather isn't working properly the issue lies elsewhere? I've got a few dribbles from the primary case and an occasional drip from the speedo drive on the gearbox but the engine is as dry as a bone.

[baz]

Surely if the timed breather isn't working properly the issue lies elsewhere? I've got a few dribbles from the primary case and an occasional drip from the speedo drive on the gearbox but the engine is as dry as a bone.

the timed breather works perfectly
there is no problem
 i'm hoping when eventually it wet sumps that it dumps the excess oil straight back into the oil tank, and maybe the extra breathing will help ?
cheers

[Swarfcut]

baz. If I've followed this we now have a direct connection from the sump to the oil tank, via a non return valve. So a sump full of oil is blown dry by the crankcase compression.

 Got to admit, that's bloody clever. As I see it you would still need your new pipe to be above the minimum sump level, otherwise the scavenge side of the pump will tend to run dry, with consequent starvation of the rockers.

 Cheers.

 Swarfy.

 

[muskrat]

G'day baz.
A bit hard to follow your description.
Could you draw a mud map of your connections?
Cheers

[baz]

G'day baz.
A bit hard to follow your description.
Could you draw a mud map of your connections?
Cheers

Basically the sump plate is connected (from underneath the oil filter) to the reed valve then to the oil tank
Cheers

[baz]

baz. If I've followed this we now have a direct connection from the sump to the oil tank, via a non return valve. So a sump full of oil is blown dry by the crankcase compression.

 Got to admit, that's bloody clever. As I see it you would still need your new pipe to be above the minimum sump level, otherwise the scavenge side of the pump will tend to run dry, with consequent starvation of the rockers.

 Cheers.

 Swarfy

Yes that's basically it
The pipe is fitted to the sump plate where the magnetic drain plug would be this is below the filter mesh so no stand pipe (as yet) the pipe then goes to the reed valve then to the oil tank breather
The oil pump scavenges fine with the reed valve inline but I noticed a slight drop in return oil volume at the oil tank if I remove the reed valve
The pipe from the sump to the reed valve is full of oil to the height of the sump pick up
No oil gets pumped out of this pipe with or without the reed valve fitted
I'm assuming the oil in the sump is at its correct level because the oil returns perfectly
I wouldn't advocate anyone else trying this incase I blow my motor
But at the moment it works fine and I don't hang about on it
What am I missing??
That's the reason I put it on here to find out if anyone else has done this ?
If the standard rotary timed breather wasn't working on this bike I would still try it but I would fit a standpipe to the height of the oil pickup pipe in the sump
Cheers

[muskrat]

G'day fellas.
This is the breathing system on my Cafe (ex race bike).

With my system the timed breather (in the motor) needs to be modified. See pic "timed breather" cut at line so the port is always open. The timed breather must stay to eliminate camshaft end float. The inlet is through the rockerbox (pic #1 the white bit is the non return valve). From where the breathing exits the crankcase (pic #2) is piped to the oil tank (pic #3) (I made a alloy central oil tank, ex race bike). Then the oil tank is vented (pic #4) to atmosphere through another non return valve (pic #5).
The Bunn breathers open and close with a fly fart, bugger all pressure so at any time there is no crankcase pressure. Pistons go up, inlet opens allowing fresh air in. Pistons go down, exhaust opens allowing blow by out to the oil tank and from there out to atmosphere.
Bunn's are no longer available but valves can be found. https://tinyurl.com/s85jlnm
This system will not stop wet sumping but instead of dumping it on the ground it goes back to the oil tank. A standard oil tank would need to be modified to allow inlet and exit. Pipe needs to be at least 3/8".
Hope this helps.
Cheers
Musky