I'm considering modifying my crankcase breather system to a DK Custom kit. For a cleaner look, I am considering going with the vented breather bolts instead of the hose setup. My issue with these is the potential for blow by coming from the bolts and covering the exterior of the bike. That could get pretty messy on a long highway ride. I currently have no issues with oil collecting at the bottom of the filter. I'm doing this strictly to eliminate the oil entering the combustion chamber. I've searched the internet and can't find any reviews that would help me with making a decision. Just a lot of PR stuff. I would really appreciate some input from anyone who has experience with the vented breather bolts.

 

 

I just Tee'd the two lines behind the carb, and ran one hose down behind the pushrod tubes and out the bottom with no filter. That oil came from the ground and anyway, not enough of it to create a bio-hazard. Another high-mile bike with no issues.

 

Personally, it's a cheap mod and can only help. I've done it to my bike. Wouldn't dissuade anybody from doing it to theirs.

That said... When it comes to the breather bolts... I think you'll get a mix of opinions/responses. Some will say they work great - no problems. Others will say - yes - they do get minor oil residue of their stuff. You'll probably get comments to the effect that only filling the oil tank to half full (should be doing this anyway) will mitigate the issue to some extent. Others may say they still get the oil residue regardless.

Personally, I'd recommend the hose approach. If done well it looks fine (I actually like the looks of how I've done it). Bonus - you'll not get oil residue on anything with the setup. Also, I put a Krankvent inline to address the potential for failing umbrella valves. Can't do that with the breather bolts.

 

I have had a set of DK "Stage 3" external breather bolts on Reaper since last summer. When I first installed them, I was getting a fair bit of oil collecting under the rear breather bolt, and a little bit from the front one. I always keep the oil level midway between add and full on the dipstick, to prevent oil accumulation in the air filter, but that didn't keep the oil mist from pooling with the external breathers. I thought maybe the umbrella valves in the engine breathers were worn out, so I got the rebuild kit and rebuilt them. That didn't make a difference. So, I did some research on the 'net, and found suggestions to increase the size of the oil return hole in the rocker support plate under the breathers (just drill it larger). Once I did that, no more oil pooling. I like the idea of not having oil mist sucked into the combustion chambers.

One thing I noticed is that when sitting at a light or anywhere stopped, idling for a bit of time, I can smell the fumes, hehehe...

Edited to add: Reaper's engine has been modded. high lift cams, bored to 98ci, running about 10.5:1 compression.

Cheers!

 

I did mine last fall, using breather bolts and tubed into a small catch can under the breather... works great. In cool weather I do get a slight film here and there. I think it is from the warm air from the engine mixing with the cooler ambient air. I even get more of a tan sludge mixture in the catch can in cool weather. Once it warms up, like now, even after a day of 300 miles of interstate/turnpike speeds all I get is a couple drops in the catch can and no misting. I also used DK's catch can and modified the foam... I switched it to lawnmower filter material and made it a bit thinner so there was a small space at the bottom and at the top, so that the filter material was not touching the vent holes on the top of the catch can. If I ever decide I want to take it off or back to original set up... its two bolts and five minutes.

 

I emailed DK Customs and they recommended not using the breather bolts for my 2015 Street Bob.

I went with the discreet breather and mounted it like the photo above.

 

The breather bolts work well on the Sportster models but as previously stated, it is possible that there can be a bit of a mess with the breather bolts and higher compression engines.

This is not to say this will be the case for sure with your bike. But it is a possibility.

 

Thanks, gents. Your input was very helpful and appreciated by me. Based on what I've read here, the hose and possibly catch can is the ticket. I do a lot of high speed long distance interstate riding and the bolts might not be the best choice for that kind of riding.

 

Double post.