To avoid my 1982 FLH getting a defect notice, I cant have the breather venting to atmosphere.As you all know the original set up was the breather going back to the air filter box .As i have a S&S super E this isnt practical nor desired .Currently i have a PCV vave which works well.My question is do i run the PCV valve with the catch can or do I eliminate it? This is the catch can iam looking at installing somewhere out of sight on my bike. Has anyone used one of these from DK Customs?

 

Wouldn't that still be venting to the atmosphere? Although it would collect liquid.

 

it vents to atmoshpere through two filters in catch can

 

The PCV valve would still be helpful to keep a vacuum in the case.

 

I know this isn't motorcycle but principle is the same.

 

Ok follow up question....what year did the factory start to route the breather back to the air filter? does any one know for sure? Why i ask is that in Australia motorcycles are exempt from the Australian Design Rules on emissions but if the motorcycle was released with the breather going back to the air filter then it has to comply with that (as is with my 1982 FLH ).
The reason i ask is that Iam the responsible person in my historic club for the Classic Vehicle Scheme run in conjunction with the state government for conditional registration. We get cheap rego and insurance $51 per year if our bikes conform with the regulations.I want to inform members that have harleys that are up to a certain age , that their bike is ok to vent to atmosphere.
We are a rules based club , so dissent isnt an option

 

1980 - up in the US,
.

 

When you figure out how to Measure any Vacuum in the case, without a "Pump" please Tell about it..
No Way I obstruct the Breather, in Any Way.. May as well just plumb the breather into the Back side of your S&S air Box (look at those Threaded Holes that have Plastic plugs in them)!! Best way to Pass, and keep the Crankcase Well Ventilated.. (close as yer gonna get to a Vacuum) When done with testing .. Remove the line and drop it to the ground...and Stick Plastic plug in back of Air Cleaner!!! If you think Yer engine is Blowing excess Oil out Breather...Which generally indicates a Problem...Starting with Too Much Oil in Tank...and Progressing to Bad Ring Seal!! A drop here and there at Most...

 

I have used the DK Customs DIY Catch Can External Breather System (2015 FLHTK). Installed in 2020 at 10k miles, when I changed the oem air filter to the Screaming Eagle Air Cleaner (29400064). DK Customs even supplies the proper drill bit in order to drill and tap my new (expensive) air cleaner, and install hoses that divert the mist into a catch can. I've attached a photo of where the catch can is located. Plenty of videos can be found on how to do the procedure.

It actually works very well, and I recommend doing it. But! Yes, but, one thing you need to make sure of, and that's to routinely check and clean the little catch can.

Last year (25k miles, 2025) I somehow totally forgot to check the can and clean it out. What a mess. Catch can got full and it all backed up in the lines and made a huge nasty mess inside my throttle body, a lot worse than before I done the bypass.

So I cleaned it all up, and decided to replace the breather assemblies (which at 25k miles it was due anyway) and also do the rocker support plate modification by drilling .125" drain holes.

After cleaning, I definetly noticed a huge difference in performance, evidently the sluggishness I never noticed probably because of the slow progression of buildup in the throttle body after the catch can got full.

So I decided to eliminate the catch can out of the modification, which I read you're unable to do, but like I said, be sure to check and clean that little can often, very often. Right now I do not have the catch can installed, I eliminated that and it just vents to atmosphere. The lines are ran down towards the front and then along the right frame rail and it ends underneath to the right of the path of my rear tire. But after repeated examination of the end I have no oily residue anywhere, not even a drip after parking. I think drilling the 1/8" holes (and new breather assemblies) all but eliminated any breather mist. There is a noticeable air flow at the end of the line so I know it's working.



Catch Can circled

No Catch Can, vent to atmosphere

 

OK, you're picking nits. I meant the descending pistons push air out of the cases, and a PCV restrict air from flowing back, resulting in lower pressure than atmospheric. It this an advantage? IDK, perhaps it keeps oil inside the motor, or maybe adds 50HP?