(Bob's note: This is a follow-up article on Arthurís Buell. If you've done any interesting modifications to your bike, send it in, your fellow members would be interested in it.)
All motors are going to need some way of dealing with oil fumes and water vapour. In the case of the Buell (and other Harley motors) there are breathers coming from each rocker box that originally fed into a series of passages in a monstrous air cleaner box. That meant that, in theory at least, the gunk was sucked into the carburettor and burnt.
A previous owner of my Buell had replaced the original air cleaner with something smaller. The vaporous by-products of combustion eventually fouled the air cleaner element and then dribbled out and down the side of the motor. The drool is an emulsion of oil and condensed water vapour.
The internet forums offered all kinds of Ďsolutionsí. The ones that were able to keep the mess off the bike usually involved an open catch can of some sort Ė often a beer can cable-tied to the frame in a conspicuous place.
I eventually designed a closed system that involves a catch tank made from the largest piece of PVC pipe with end caps that I could fit under the fuel tank. Threaded brass fittings connect the two rocker box breathers to one end. At the other end one brass fitting connects a return tube to the air cleaner and another connects to a drain tube that runs down to a captive plug under the bike where I can get to it easily.
I used radiator over-flow tubing because itís supple and so far hasnít been bothered by heat. I used a garden irrigation fitting to get a tight right angle bend in the return tube. An unravelled stainless steel kitchen scrub bud is in the catch tank so that the vapours have something to condense onto.
The brass fittings for the hoses from the breathers and back to the air cleaner are as high up as possible on opposite ends of the tube. The fitting for the drain hose is as low down as possible on its end. The drain fitting is also positioned so that when the bike is on the side-stand itís at the lowest point and ready to empty the tank Ė best done while the motor is still hot after a run.
The mess of cable ties and bits of rubber used to mount the tank and avoid vibration damage is safely hidden under the fuel tank. I suppose I really should devise an elegant bracket and sprayed the catch tank with black vinyl dye.
After a two-fuel-tank ride I can drain more than a tablespoon of watery drool from the catch tank. There is usually a smear of oil in the air cleaner housing that shows that some oil vapour is getting drawn in there Ėit will probably help lubricate the carburettor slide!
I only once had a mess dribbling out of the air cleaner but on that occasion Iíd forgotten to drain the tank after rides that totalled at least 1150 km. I guess the catch tank wasnít big enough to cope with such neglect!
The basic principles here would apply to any bike that has a breather system that you want to keep as a closed loop. I could easily run the outlet pipe to the back of the bike and keep the catch tank to just collect the condensation or I could just run the breather hoses out the back and dump the whole lot onto whoever is behind me!