Sorry I don’t agree. If you route the oil breather outside of the filter the element will become saturated with oil – you want the fumes to be sucked into the carb and burnt and the slight suction is downstream of the filer element. For the fuel breather it’s better to have the petrol fumes enclosed within the air-filter and drawn into the carb rather than hope they get sucked through the filter element. And don’t use pancake air-filters.
Haven't seen these. Can you point me to one as that makes sense for the crankcase. Presumably fuel tank one is OK straight into the K&N?
Yes, it will work but I prefer to keep the fuel breather completely separate to the crankcase breather. It’s easy enough to drill each filter top and screw in a barb fitting.
They’re available in several sizes; this one is 5/8”. http://www.burtonpower.com/k-n-breather-pipe-adaptor-5-8in-kn85-1362.html IMO they’re for people who for whatever reason are unable to drill a hole. Better than nothing or venting directly to atmosphere but it cannot provide positive crankcase ventilation because there is virtually no negative pressure outboard of the air-filter element. I suggest you vent both fuel and crankcase breathers’ inboard of the filter element – just like VW did.
You'd need to make sure the breather hose has got a reasonable ID in case your pistons are chuffing a bit, otherwise the case may start pumping itself up. Redoing mine at the mo - well, connecting them up, as the heating stinks. I ran two hoses, one through the top of each air filter. Also ran the tank breather to a separate connection on one of the filters. I've got a CB Performance breather tower, for no other reason than the oil filler's in a handy place (everything else leaked like a sieve). Did enable me to stuff half a Persil pan scourer in as an oil separator. Seems to work.
And leak from the front. And the NPT tappings were done with...I'm not sure what. Certainly not an NPT tap. A spoon? However, after applying half a pound of Curil-T to everything, it stopped leaking, and is much better for oil-filling. The filler points straight at you.
It’s a Type 4, the standard crankcase breather hose is fine, whatever size it is – about 12 or 13mm bore from memory. I’m reasonably sure I used ½“ barb fittings in both filter covers with the standard VW reducer for the fuel breather.
Mine ...been like it 10 years ..fuel and case in same filter ...I don’t see the reason for separation ?
Home made , 12 mm id to case and what ever the fuel breather is .... Never have an issue with the carb ( Dell) and no dirtier than the other side
I keep them separate because as far as I know you can’t buy a fitting to take both and rather than have two fittings in one filter I put one in each. There will also be slight pressure differences between the fuel and case breathers and there could be cross contamination, probably not likely but it is a possibility and you don’t want petrol fumes in the crankcase.
