Every Harley is different. I have 3 and only 1 needed the external breather. It also happened to be the bike that had the most crankcase pressure. If your bike is venting little to no oil, I wouldn't worry about it. Guys that are running modified motors, Stage IV, big bore, etc, the vented dipstick probably wouldn't be a bad idea either.

 

Been running an external breather for a while, and after seeing the s**t it collects, I think it was a good move to install it on my bike.

I found the smallest 'Oil Catch Can' I saw on eBay which had a top mount and also had fitted the internal mist filters. I originally ran 2.5mm rubber tubing from the breather bolts, but found that this tubing did not allow sufficient flow, as I noticed that the rear rocker cover started seeping oil soon after installing the catch can. I later replaced the 2.5mm tubing with 5mm Braided Stainless line (as pictured) and rocker cover leak stopped.

The Catch Can is fitted to the horn mount, and horn relocated under steering head between down tubes (with no chrome cover)

This set-up may look ugly to some out there, but I couldn't give two f**ks if it does the good job it is supposed to do, and stops (or lessens) the carbon build up over time.

 

Is anyone having issues with this on the M8? My TC used to leak like a sieve through the air cleaner, but my old EVO never had issues. Always left the oil bags half a quart low, and I’m doing the same on my M8

 

while not the most appealing location, it is not awful, but more importantly, it is effective, and you are happy with it

 

Are you OK with removing Harley engineered lubrication to the upper piston ring? Also increasing compression and pinging that can be had with continued use?

 

Are you saying that Harley designed the breather system to inject oil into the intake as a method of lubricating the ring, and that removing that oil will also increase compression?

 

what an ignorant statement! you do realize, introducing oil into the combustion chamber, lowers the effective octane rating?

 

I had the exact opposite experience. my twin cam never puked a drop with the oil level set pretty much at the full mark when hot. My 92 evo (bottom breather) puked like crazy. So far so good with my m8. I believe the breather bypass is necessary for some (the pukers) but not all HD motors.

 

Me too, no problems with my 2020 M8.

 

why do you think Harley starts out with such low compression to begin with. They know by injecting breather oil they eventually will get to the proper compression. By removing the breather oil you are messing with designed improvement.