First post, so please be gentle!
My A10 Super Rocket (1958) has just started blowing oil out of the breather pipe. It has never done this before. The pipe is the one that exits behind the Primary chaincase and is carried by a flexible pipe to the rear of the bike. It is worse when the engine has been stood but even when warm, having been ridden, there is a continuous stream of pressurised vapour coming from it that has frothy oil in it!
Has anyone got any thoughts on this?
Cheers in advance.
Welcome to the BSAOC forum.
I've got an A10 but can't help.
Hi,
Usually there will be no oil exiting from this breather but a possibility of a very slightly oiliness to the air that blows out.
When the bike has been stood its i likely that what continues to come out is oil mist that has condensed in the tube.
The breather is timed through the timing gears and is controlled by the 'top hat' on the end of the camshaft and the cork that sits under it. If the cork has failed then the timing of the breather will be compromised as the gasses will escape at the wrong time. However, I have never heard of a sudden failure of the cork but rather a decline in its function.
If for some reason there has been a failure of piston rings then the crank case will get pressurised and potentially blow oil along with air out of the breather. This will be made worse if the cork is not 100%.
Have you noticed any new seepage or leaks any where? This could also indicate crankcase pressure.
Perhaps a course of action could be to check the cork.
Take the outer timing cover off and you will see the 'top hat' poking through the inner case.
Try and move it in and out any perceptible movement means it needs to be replaced.
As well, or alternatively, check the plugs for oiliness and even do a compression test.
Dave.
it could be too much oil in the sump and partially blocked oil return or PRV
Hi,
One I forgot is that the pick up pipe in the sump can drop out allowing too much oil in the sump.
Remove the sump plate to check.
Dave.
Thanks for the replies.
That's my weekend sorted out for "Things to do"!
I don't believe that its rings, as it has been re sleeved and new (STD) pistons fitted. But the sump will be coming off, regardless. The rebuild included a brand new cork washer. There was no end float on the top hat. This all points to the sump being the issue.
Thanks again
Bill
Often with an A10 if it's wet sumped, it will fill the primary chain case. When the motor starts up, the oil will get past the felt gasket on the sliding plate and leak all over the floor.
Remove the level screw from the chain case and see how much comes out! Then put fresh in the oil tank and start again.
I replaced the pump on mine and this stopped the wet sumping and made the bike 99% leak free... least that was till the oil tank split. Then it lost 100% of its oil 🤣