I am starting to look into doing something like this myself. I recently installed a K & N RK-3956 on my 22 FLTH and noticed some crud on the butterfly valve with only about 3500 miles on her. Gonna check it again this weekend, but wondering if I still have that option with the K & N filter kit I installed. I emailed K & N to ask how it was vented since I didn't think to look while installing it and this was their reply ("The crankcase vents internally are on the back of the back plate and vent into the throttle body."). But if I can still vent them externally I am going to.
I am curious though for those that have done this. Did you guys need to vent the crank case also? It doesn't look like it is necessary for my bike or after 2020, and after reading this ( https://cdn.shopify.com/s/files/1/00...f?v=1659048640 ) I am not certain. I was thinking about doing the transmission cover from Trask or something similar.
I used the existing venting hardware on the inside of the air breather. Brought it to a 'T' fitting connected to a vacuum line. Drilled a small hole in the back of the plate that I fed the vacuum line thru (very tight fit). Brought the line down the front of the motor, then under the frame to about half way under. I've put about 300 miles on it so far and its venting nicely down below. Inspected it twice for functionality and yeah its working well. No leakage inside the air box and the small amount of oil mist that is expelled is going right out into the atmosphere. First time in its life the engine is getting programmed fuel instead of forced oil in the mix. Exhaust is clean. Not as elaborate as my venting in the past but on this model I had rubber grommets that snapped into the breather bolts with a curved hose on the end going into the TB. I inserted 3/16 brake line into the curved openings then into clear tubing ( for visual inspections) then into the T fitting. Viola!
I used the existing venting hardware on the inside of the air breather. Brought it to a 'T' fitting connected to a vacuum line. Drilled a small hole in the back of the plate that I fed the vacuum line thru (very tight fit). Brought the line down the front of the motor, then under the frame to about half way under. I've put about 300 miles on it so far and its venting nicely down below. Inspected it twice for functionality and yeah its working well. No leakage inside the air box and the small amount of oil mist that is expelled is going right out into the atmosphere. First time in its life the engine is getting programmed fuel instead of forced oil in the mix. Exhaust is clean. Not as elaborate as my venting in the past but on this model I had rubber grommets that snapped into the breather bolts with a curved hose on the end going into the TB. I inserted 3/16 brake line into the curved openings then into clear tubing ( for visual inspections) then into the T fitting. Viola!
You must have a M8, how about a picture of your work, thanks
Similar idea, using the "T" with the original tubes, but used fittings to get thru the back plate... and I have since shortened the vertical hose, so it all "sags" downward, to help gravity do its thing.
Pic was snapped after getting caught out in the rain.
Similar idea, using the "T" with the original tubes, but used fittings to get thru the back plate... and I have since shortened the vertical hose, so it all "sags" downward, to help gravity do its thing.
Pic was snapped after getting caught out in the rain.
yes very similar and very effective.....I prefer to angle the lines slightly downward which would allow gravity to assist any oil with draining downward. If it doesnt flow down it'll want to pool and work it's way out. If you get seepage and oily residue on any of the joints or couplings thats what you got going on. It should stay clean of any oil or it'll find its way down the Throttlebody.
I did that same exact thing on my last bike with 103 HO. Hardly got anything out of the breather. These M8’s aren’t quite that easy, with the drilling and tapping that’s necessary. I’m still not completely sold on the concept of external breathers though. I’ve had them on a few performance cars, just because it seemed like a good idea, but never saw much oil in the can at all. Probably would become more critical when the miles get high. The other thing too is that venting the breathers externally makes the crankcase vent passively instead of actively by vacuum. I wonder how much the crankcase pressure is affected between stock and vented?
03-20-2023 | 10:43 AM
