Just thought I would share.

I installed an external breather on my 2020 Fatboy. Honestly I was unsure about the whole idea of the external breather, but when I saw the YouTube video by Doc Harley (I trust his views), I decided to go ahead and install one.

For those ot you who don’t know, Harley engines (the M8 anyway) vent hot air and oil mist back into the air cleaner intake for EPA reasons. An external breather takes that hot air and oil mist and vents it into an external “catch can” or filter, directing it away from the engine air cleaner intake. The idea, as I understand it is to keep that hot, bad air and oil mist out of the intake, resulting in a cooler running engine and cleaner intake.

I was skeptical about the whole idea, and read mixed things about the mod on this forum. However, after seeing Doc Harley’s video, and “endorsement” as a good idea, I did the mod.

Very easy to do. Took me about 30 min.

Can’t say I notice anything different, but it makes me feel better.

R,
Sanjuro

 

Many thanks brother., This is completely new. Had no idea about this crankcase breather thingamabob. Definitely gonna get right on it!
I’m sure others will too!

 

Sorry we can’t all be all knowing like you...

 

Hi,

There's a recent thread on this subject. An M8 with 6 miles on the clock when the external breather was put on, I think around 10,000 miles later, looked the same as one without. Endoscope photos were posted. Looks like the carbon on the pistons is one of the M8's endearing characteristics. Could be modern fuel, or blow by the rings, but the breather doesn't seem to be a solution.

On the one hand, it makes sense that you wouldn't choose to put hot oily air into the combustion chamber.
On the other hand, it's probably an incredibly small amount each cycle and if it damaged the engine, why would so many manufacturers do it and still offer lengthy warranties (sometimes unlimited mileage)?

I decided not to worry about it.

 

Pay him no mind. I've thought about doing that for a long time, and I've had the parts laying around forever. I might just give it a try.

 

When you dump that catch can the first time it'll make you feel better that **** isn't going back into your engine. Not every Harley needs it. If you have oil in your air filter (a significant amount) then you need it. I've only had one bike that I did it on. Drill a couple of holes, use your and or buy some breather bolts, some rubber hose and a T, and that's it. Oh, and a catch can.

If you have oil in your filter make sure it isn't a more serious issue with your engine. When perfectly fine engines do it it'll have you scratching your head...

 

Put mine on one year after I won my motorcycle. Been on for the last 7 years. I only run ethanol free gas also. Think I will buy or rent a scope to take a look this winter when I do a stage 2 if I can find the time.

 

Just did mine before winter , made my own catch can , finishing up stage 2 now , engine should be happy now .

 

The oil vapors being routed to the throttle body for a "reburn" has been dictated for a long time by the EPS. Oil vapor needs a higher temp. to burn off completely. Most modern cars, trucks, etc. have been doing this for a long time. On ported fuel injection engines the fuel is injected onto the intake valve and that helps to keep the carbon buildup to a minimum. Gas direct injection is injecting fuel straight into the combustion chamber with out cleaning the valves of carbon build up. Fuel selection is critical in keeping the combustion chamber clean. Use a Top Tier fuel, it has the required amount of detergents in it to maintain the Top Tier qualifications, it's only a few cents more per gallon. Just look for the sticker on the pump.

 

Check out DK Customs, they have good informational section on external breathers.