- mine doesn't leak , at all.

- perhaps go through the "easier" checklist first , eg :

1. overfilled oil
2. ball-check valve in oil pump (and the ball's seat)
3. go with a dino-based oil with a heavier viscosity
4. make sure to use correct oil filter
5. make sure air-filter is clean.

- if you get the oil-leak through the breather hose
after the bike's been parked for a while , its likely
the check valve.

- cheers and do let us know how you pan out.

.

 

My L84 electraglide hurled oil out the breather. I just re-routed the breather hose into my oil tank and no leaks. Not normal to do this but it works.

 

I also have an evo/ street ported heads, ev27 cam. used to get a little oil in the air cleaner when cruising fast for long periods (80-90 all day). Did the trick an earlier reply mentioned. Drill out the oil return hole a little bigger. now there is no oil leakage at all. Even holding 90-95mph for hours still no leak. The EVO trully is a great motor.
I now have a new bike with the 96" twinky, I like it too, but if I had to sell one...I would keep the old heritage with the evo. It has more character, and gets better milage. It's over ten years old now, and still doesn't leak a drop.

 

I'll throw my little opinion in as well. Learned alot from the guys here the past few years and you have to remember our bikes are older. That means that rubber and gaskets get brittle and fail. Mine's a 93 FXLR and had the same problem you have after changing my cam to an EV-27 instaling new lifters and adjustable pushrods. Harley designed the head breather engines to route the oil mist through the carb I believe for EPA reasons. Mine got so bad that oil would hit a discolor the rear heatshield.

Using some tips from the members I've over the course of two years I rebuilt the engine and entire bike with some help from my friends. Installed an 85" kit with ported SE heads, roller rockers and a V-Thunder .585 lift cam to compliment the ported SE heads. While doing this, I also installed an S&S reed valve breather, S&S rocker boxes that use a different style larger umbrella valve built into the gasket, and a Drag Specialties chrome crossover between the heads with 3/8" braided line running between the engine and transmission and under the transmission. I also installed the Hayden oil fix jets between the cylinders and cases. All the rubber oil lines and vacuum lines were also replaced.

EMGO makes a plastic 3/8" filter with a washable element like a K&N filter. It also has a tab for a wire tie and can be cleaned, reinstalled and the mist reoils it automatically. The combination of the above listed parts eliminated the problem entirely even on long hard runs. I can't put my finger on any one particular item that solved the problem.

IMO and in your case, the crossover breather tube, 3/8" line of your choice and EMGO filter
should help or maybe solve your problem without having to take the engine apart. If the engine comes down, then new umbrella valves, John's larger return drilling in the rocker boxes and new top end gaskets are in order. Installing the Hayden kit along with new James base gaskets will prevent those dreaded base gasket leaks from ever starting.

Good luck with yours whatever you decide to do. It can be done and mine does not drip a drop.