I posted a pic of my breather bypass that I implemented during my FM big-bore install. I have received a few questions about it so I thought I would address everything here. Since the original pic I did a little re-engineering to curb some of the oil vapor that was getting onto the exhaust. First, the list of parts I've used, including the recent revisions:

1. Golan Products Gearbox Breather https://www.denniskirk.com/golan-pro...prd/189438.sku
2. 3/16" & 5/16" clear tubing
3. Visu-Filter, fuel, PN 8423-01-9909
   https://www.amazon.com/gp/product/B00SJWGHJY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
   https://www.amazon.com/gp/product/B00SJWGHJY/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1
4. JB Weld Multi-Purpose epoxy
5. 3/8" spring clamp

The basic setup looks like this:



After a few hundred miles of use it was apparent that vapor and some liquid was coming out of the vent holes on top of the can. The can has a dense-foam filter inside of it that fills the entire cavity. Since the top of the filter would saturate first, it allowed some oil to come through the vent holes. You can see some of this mess below. I wasn't having any of that.



Here you can see the inlet to the can. The foam filter sits up inside there:



I wanted to eliminate the foam from actually absorbing oil, and also wanted to move the outlet deeper into the can. I had the idea of using a small fuel filer to do the job. I have already remove a nipple that wouldn't be used, and sanded off the barbs on the inlet side:


I then cut the original foam filter to be used as gasket and vapor barrier, and drilled some drian holes into the bottom of the filter body:



I then added another foam piece to have a secondary barrier:


Now when the can is screwed on all liquid stays in the bottom where it belongs, until I drain it. There has been very little captured so I don't have to drain it often. Now it works like I intended it to and I have no further leakage, and the bike and air cleaner stay nice and clean.

The filter is epoxied into the inlet hole.

 

 

Good job.

 

 

the entire AC system mods are very creative, functional and clean looking...very impressed..best one I've seen so far

 

A nice design, but I think that filter is going to get clogged with goo since it's only designed to have gas pass through, once clogged you effectively have no breathers. I may be wrong, but I'd like to see what it looks like after a few thousand miles. I have the same style breather can that I haven't installed yet & I wondered about the foam also, think I'll try it without the foam. Keep us informed as you put some miles on it.

 

That could be possible, but I do have a plan 'B' if it plugs up in any way. I'll simply cut the bottom tip off and remove the sintered filter. I would not advise simply removing the foam filter; the oil needs to be directed to the bottom of the can and then a barrier in place to keep it from being pushed/sucked out of the vent holes. I think wind was creating enough turbulence around mine that it helped pull some oil through the vents. After I get some miles on the current setup I'll report my findings. I'll lick this sucker on way or another.

 

Just a follow-up. I have put a couple hundred spirited miles on the bike since I made this revision and it completely eliminated any external leakage. I have emptied the can twice, and it was almost clear water, less than 10% full. That was good to see, as this confirms very little blow-by from the new jugs and pistons. I'm happy with the result.

 

My vapors exit the air filter via a length of fuel line hose - which terminates beneath the bike about 1.5 - 2 inches below the frame rail. Nothing to check, nothing to clean; I'm a simple guy.

 

I did that and I was getting oily mist all over the back of my bags, pipes.