I've a K&N air filter kit on my 07 Softail Standard. I was getting some sporadic oil dripping from the air cleaner. I designed a system utilizing my stock breather bolts tied to a tee inside the filter area and running out a drilled hole in the filter backing plate. The hose then goes up and between the cylinder heads over to an oil catch can mounted to the horn mount.

I believe the factory breather bolts have internal check valves and that's a bit of a concern to me since the breather lines run uphill.

My question is; Will the stock breather bolts allow oil to drain back to the engine through them? If not can I simply drill them out so they will?

 

The poppet valves are one way out. Usually, the drips you see are what collects in the line and after bike sits awhile blows out on a run. If you drive ever day, you see very little day to day. The are not in the bolts but back in the baffle box in the top under the rocker covers.

 

So... with about 6" of 1/4" ID hose and maybe 3" to 4" of 1/2" ID hose that oil could potentially be filling up you don't see that as a problem? I just don't want to put too much back pressure on the breather system.

 

Not sure how you would know how much drag resistance would be on the hose. I firmly believe we should all do our part in obeying the law of not doing that. There is not enough of suction going into intake to actual pull raw oil into intake.. Just the air mostly since aonly atmospheric pressure is behind the push unlike the driving pressure of the pistons pushing out exhaust. What people see they think is oil is actually dried fuel that is left in the intake from the injectors since they are not timed spray and spray until you kill ignition.. Not sure since you have why you just did not come off the breather connections to you catch can. Be sure you put a filter on the end since with that small amount of overlap in the single pin crank that causes that small amount of vacuum on that line. If you ever hook a vacuum gage on a V-twin, yo will see what I mean. That is why it takes a twin column of oil to balance the older dual carbs.
Do not ever drill out the bottom of that drain hole in the baffle. There is all kinds of stuff showing that, Problem is, by doing that, instead of the vent air going into and 180 thru the baffle plate (that turn helps oil fall out), it blast straight up thru the medium.

 

I guess I'll find out if it's fuel, not oil. I highly doubt it's fuel as the viscosity is very similar to oil. There's also no fuel smell to it either. Anyways, it'll be very easy to convert back to the factory system otherwise.

I did come off the breather connections, teeing them together and then to the catch-can which is filtered too. The vapor/oil comes into the top of he catch-can, down through the filter media and down into the can.

 

I was referring what people see in throttle body when it is attached to vent. What you are seeing is some moisture from combustion process, some oil that has gotten past baffle as a fine mist mixed with the blow-by that has came down thru the small ring gap and of course what has fallen out in the hose and ran down.

 

Funny that you mention that...

I had installed my new external breather system, up to but not including the catch can. I let the hose that would go to the catch can hang in between the cylinders. The breather bolts were 100% sealed from discharging into the air filter area. I took a 3 hour ride with it yesterday with the new system installed.

Fast forward to this afternoon. I finally received the catch can from, J&P. I was getting ready to install it. Having second thoughts about the breather hoses going uphill above the breather bolts I decided to pull the air filter off to see if I could redesign it so it would drain downhill to eliminate any breather back pressure caused by the column of oil. When I pulled off the filter there was that same oily liquid inside as there was before. I checked all breather hose connections and the were good and tight, not leaking oil at all. The only place it could be coming from is the throttle body inlet. I'll post a picture of my breather mods.

What are your thoughts? BTW, thanks for all your help!

 

Now I see what you are up against on your version of Harley's vents. That is why I was a little confused about you inside air box and out. My older SE backing plate has an S shaped hose coming off the breather bolts coming down, enter the back side of the back cover and doing a 90 way off to the side like yours and aiming down. Your box is closer to motor to probably trim it back for knee room. If you are bound and determined to get the vent to the outside which I don not support, I think one of our sponsors D K Custom (super cool man) on here sure does and has a breather bolt that has a pipe off them that keep all that outside the breather box. Not sure how long you plan on keeping bike but with heat and vibration, I would be concerned about all that coming loose and going into intake. If he can fix you up, patch that hole you drilled with a pop rivet and two stainless steel washers from the specialty section of ACE. The oversize thin ones they have a small hole and rather large diameter

Interesting but my Yamaha V-Star 1100 Custom vents similar to Harley into the air box and the hose is routed down to a small walled cup at the bottom. Coming out of the bottom off this cup is a short hose with a cap to drain off oil. This drain is not mentioned anywhere in my Yamaha OEM factory service manual and I did not notice it. When I did the 10K check, that cup in the air box has 3 or 4 ounces of oil and of course it had migrated all over everything on the bottom. The motor turns almost 1000 rpm higher then my Harley and it does vent a little more. But now, I just dump it ever 1000 or so.

 

I had hi-lighted your post about the fuel coming out of the throttle body. As I said, There was a substantial amount of viscous liquid (same color as oil) in the filter box that COULD NOT have come from the breather bolts. I was curious what your thought was on that. You'd made a comment that it could be some fuel reversion.

 

Just my opinion but what you see in your original system and I assume that left hose is original and was just turned downward (what mine do but they go thru and go up hooking on the breather bolt..and I have replace them once since heat made the fall apart) is oil. And sure some does get into intake. However, most that you see past throttle plate is dried gelled fuel from the injector just a little back further in. That last spray cooks dry at ever hot shut off.

Just my opinion. but why I say that is it is rarely at the mouth of the throttle body before the butterfly. Is fuel reversion a correct term for this ignition kill cutoff leaving that charge? Don't think so. However, to solve it, that is why cars and now Harley have gone to throttle by wire. That system even throws a shot of air by opening butterfly with no fuel if you let up on the gas quickly and you can see it in a tac bump even though you are total off throttle.

By any chance, Have I seen that car of yours at the Hampton Cup boat race on the bridge?