With the velocity stacks and snorkel measured up and squirreled away in CAD, it was time to rebuild the airbox …… except billy-butter-fingers here, went and knocked the airbox base off a chair onto the floor – not far – but enough for it to land awkward and break the spigot for the crankcase vent. Unfortunately the spare I’d made, I gave away to a friend last year! So there I am trying to remember where I’d bought the bits to make another one, when I had a “Stop the bus!” moment …… don’t waste time and fuel going into town, sit down, draw something in CAD and print that puppy! 😀
Here’s the finished article …. it has a slightly larger inlet/outlet cross-section, although the previous one worked just fine and this time the fit for the grey pipe is better. internally there is a chamber to help reduce gas flow and (hopefully) convince some of the oil to condense and run back down into the crankcase, not out into the airbox. That’s the theory anyway, but it’ll probably turn out to be complete bollocks! Either way, it looks neater so that’s a positive step forward ……. now, what else can I break today! 😀
The MK1 vent did well and lasted almost 2 years (37K miles) and in that time I never had a moments issue with oil in the airbox going where it shouldn’t. Let’s hope this one does as well!
You may (or may not!) have read the post a couple of months ago – Fixing a few Capo niggles. That was where between Continental trips, the original air-box molded connection for the crank-case vent was drilled out and a new 90° bulkhead coupling and pipe fitted to drain any oil into the front of the airbox, well away from the throttle body and IACV (Idle Air Control Valve).
Now with the Caponord seriously (+1,000 miles) overdue a service, I got stuck in and removed the tank ready for plugs/air filter. I admit to being really pleased to see no oil what so ever in the upper part of the airbox and only a tell-tale smear in the front section. A syringe sucked what oil there was from the drain tube – approx. 5cc @ 3,000 miles WITH the oil tank filled to the HIGH mark.
Previously it didn’t seem to matter where the oil tank level was, oil kept getting thrown into the airbox and sucked down into the throttle body. Look closely at the design of the airbox and you see the ‘fenced’ in area (red) around the velocity stacks – and of course, the two slots in the stacks (arrows) for excess oil to drain through.
It’s pretty obvious then that Aprilia/Rotax EXPECTED regurgitated oil – and tried to ensure it was fed back to the engine and burnt. Unfortunately that isn’t always the case and when some bikes are left on the side-stand oil manages to get over the ‘fence’ and muck up places it shouldn’t!
Of course a little hot oil can spread a long way and look far worse than it really is ….. I guess it just niggled the hell out of me each time I lifted the airbox lid. In hindsight it’s one of those quick jobs I wish I’d done years ago.
One niggle that has wound me up more than anything about the Capo over the years, is its unerring ability to regurgitate oil into the airbox – apparently no matter how much or little I fill the oil tank. In the end, enough is enough, time to do something about it.
So this is it, remove the molded spigot/structure into the airbox and replace with a new low-profile 90° coupling and pipe to dump regurgitated oil into the front section of the airbox, from where it can be drained off via the extended drain-line down by the oil filter. Hopefully no more lumpy idle and intermittent ‘cough’ coming off idle after extended (12Hrs+) runs at motorway speeds from the vented oil draining down into the throttle bodies. A better fix of course would be to build a trap before the airbox that would allow oil to drain back the way it came while still passing vapour into the airbox. That’ll wait until winter, for now I’m hoping this will work good enough.
Secondly, and I don’t mind admitting when a change to the Capo doesn’t work – I’ve gone back to the #60 clutch oil jet from the #40. Why? Simply because the benefits were outweighed by the losses …… yes the #40 jet made the initial 1st gear selection go from ‘CLONK’ to ‘clonk’ but it also buggered up all subsequent gear changes, gone was the silky smooth shift that I’d had with the #60 jet. In the end I would say that if your Capo shifts gears smoothly and doesn’t have an issue selecting Neutral, then leave well alone. I’m sure for those with no jet, a blocked jet or a nasty gear shift this may well be a worthwhile modification, for me I’m glad to have the old slick-shift gearbox back again.