In my world, shed-life is not linear, few things progress smoothly and when they nearly inevitably turn to custard I tend to park them and let my subconcious quietly gnaw away at problems like a dog quietly gnaws away at a bone, while I conciously move onto something else (like, is it beer o'clock yet?).
If you recall from previous posts the 851 has had multiple issues with pumping oil into the airbox.
It turns out the ol' girl is not a unicorn, with a few folks offering similar experiences, even with supposedly healthy engines. It sems oil level in shallow sump engines is critical, less really is more, with a lower level alleviating the problem somewhat. Over time my engine had been healthy but pumped oil, then was unhealthy (see the broken oil ring below) and pumped even more oil:
It was made healthy again, and I'd made some mods to the crankcase breather system (PCV transferred to airbox per later race bikes, effectively increasing crankcase volume) but still the thing subscribed to the Exxon Valdez school of oil containment:
My concious mind, being from the left hand side of the intelligence bell-curve, obviously wasn't up to the job, so I figured I'd just ignore the puppy dog eyes the ol' girl gave me ("I'm sooooorry...!") and just let things percolate in the back of my mind.
Amongst my musings was wondering about the Corsa replacement for the OEM crankase oil/air separator, the Corsa unit being a XXXL sized carbon fibre box, not dissimilar to the size of a shoebox cut in half:
The carbon undertail I previously fitted is basically the bottom panel from one of these. Replica's of these things are actually not hard to find, the problem is that they take up all the space where my ECU currently sits. So to fit one you need to relocate the ECU up the front, with the necessary mounting gubbins, and especially the wiring loom, much much harder to find.
Ok subconcious, time to earn your keep: show me the magic! (waiting...waiting...waiting...) Er, subconcious? (silence) Anyone home? (image of tumbleweeds blowing around inside my skull) Bugger...
Nah, it was obvious crankcase pressurisation and oil misting was a problem from day dot and they'd replaced the OEM unit for a reason. So I started taking a harder look at the OEM breather box, which is a tiny lil' pancake in comparison to the above:
Only briefly restrained by a quick confirmation of replacement value being next to nothing, curiosity finally got the better of me: lets cut it open and see what's inside!
Expecting to see some sort of demister pad, or mesh, gauze, labyrinth paths or something to coalesce the oil or cause oil/air separation, I was gobsmacked to find absolutely nothing...not even remnants of anything...just a space as empty as the thought bubble above my head. What. The. Fcuk?!
Moving the crankcase PCV up to the airbox adds the breather box and hose volumes to the crankcase volume, reducing crankcase pressurisation and therefore pumping losses. Both rods are on the same crank pin remember, so at some point in the cycle both pistons are rising and falling at the same time, unlike an IL4 where the pistons cancel each other out.
So pumping a fair amount of oily mist is inescapable, especially when things are thrashing around at 11000rpm. And to put the PCV up at the airbox you need a Corse breather like this to replace it at the crankcase, basically a completely gutted PCV, just a tad larger (25mm Corse vs 22mm OEM outlet size, from my beer addled memory).
So lemme think about this: the oily mist is pumped through an empty fitting, through an empty box ....and I'm wondering why oil is getting into the airbox? Really, how could it not?!
So 2 things seemed obvious:
1. I needed to reinstall a "proper" PCV with reed valve at the crankcase. Easy peasey, unscrew one, screw on the other = job done.
2. Fit a genuine oil/air separator. Hmmm, not so easy, not so peasey, not if I didn't want to scour the 'net and my wallet to find the right parts, and the money to pay for them.
But demisting vapours is an inherent part of the process where I work. Some of it is fairly high tech but most of it is super simple. Me being me, and working with the inherent limitations therein, I opted for the latter path: you just need something for the droplets to coalesce/accumulate on and somewhere for them to drain back to.
Packaging/positioning was always going to be an issue but I thought I could juuuust squeeze something under the tail hump.
The first step was to roll-wrap some carbon fibre around a cardboard shipping tube to make a cylinder:
...then turn up a couple of inlet/outlet spigots from a broken 22mm carbon fibre handlebar tube. A couple of end plates and a dividing plate/baffle were cut from pre-fabricated 2mm carbon plate. The baffle effectively doubles the length of the flow path, forcing the vapour to make 2 passes of the tube. The whole thing is filled with stainless steel "wool": as the mist flows through the separator the oil droplets contact and coalesce on the wool, and once accumulated gravity drain back to the crankcase, leaving (hopefully!) oil free air to enter the airbox. The baffle is angled to encourage accumulated oil to drain towards the air inlet/oil outlet.
It's just a case of bonding it all together with epoxy and then trying to squeeeeeze the hoses under the seat (the foam pad above is to cushion it against the subframe rail).
So far so good during a quick dyno run, but life is getting in the way of a serious hit-out.
Update: a helpful gent (thanks Bill) pointed out something I had neglected to mention, so I thought I better point out that the port for the breather valve is not completely open to the elements inside the engine. If you remove the valve it's not like you are staring through an open window directly into the bowels of hell, there is a baffle integrated into the 'cases (circled on the 'case set below) with the port situated at about the top of the circle on the r/hand (upper) case half:
It won't do much to remove oil mist from the crankcase vapours, but will at least stop oil splashing directly up into the breather valve area.
