Just had a lucky one.

One that enjoys large flowing roundabouts, my commute home takes in a few that I tackle with enthusiasm. Last night, low on fuel I took a more urban route that takes in a fuel station. Arriving home, I parked up on shallow gradients leading up to my garage. Unlocked and rolled the Breva 750 in. Turned to leave and see glistening in the twilight a puddle on the concrete. Dip a finger in, yep oil. Check round the head N base gaskets. Nothing. Note a trace on the balance pipe. Then get a smear off a pipe from the rear of the sump. Squeeze the pipe and feel it collapse along a seam. Yep, split sump breather hose. Glad it happened on a bimble commute home and not on a sustained motorway run. That could have seen the motor off. Or worse.

Well spotted!

I’m confused. Why does a split breather hose cause your bike to lose oil ? Is this something I ought to check for regularly ?

This is the hose that comes out the back of the sump and goes to the air box.

56 plate Breva 750 45,000miles use between October and April (so sees only the worst time of year only).
To be fair the thermal shroud was displaced and presumably vibrated up the hose to the airbox end so leaving the low section expose to radiant exhaust heat and road spray.

I would suggest an annual inspection for cracks would be good practice.


It’s a direct connection to the crankcase. If open to air, it will just blow all the contents out. Ergo has to go to some sort of breather collector box to reclaim the oil and return it to the sump.

My LM once lost 2 litres by doing a sustained 5,000 rpm for 2 hours on the M6. I had previously replaced all the breather system during a rebuild, so thought I’d done something wrong or the new ball valve was no good. But when I looked at it all was as it should be. I could only conclude shouldn’t have been doing 5,000 rpm for two hours. shrug