External Breather Bolt question
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Cruiser
Joined: May 2017
Posts: 180
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From: California
External Breather Bolt question
I installed some external breather bolts on my nightster quite a few months ago. I found some breather bolts on ebay and used some tubing and a tee fitting I picked up at the auto parts store to run a hose down to the bottom of my bike. I'm concerned that I have yet to see any type of oil drops or mist coming from the breather bolts or hose. I cleaned my air filter yesterday and inspected everything. I didn't have any traces of oil on either the breather bolts banjo fitting or hose. Any thoughts? Coincidentally. I noticed the beginning of a rocker box leak. I know this is common for the mileage (11K) but I'm wondering if this could be a result of it having trouble breathing. I would appreciate any advice or guidance, thanks.
Road Master
Joined: Aug 2019
Posts: 786
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From: wv
If they screw in too far I hear they plug up the airway hole in the head. I'd take them out, look in the hole. and do some measuring. The rocker leak could be from pressure buildup I suppose. Did it blow the dipstick out?
Good luck.
Good luck.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
Umbrellas valves bad and allowing air to be sucked back in. Too much crankcase pressure builds and results in gasket leaks. Especially rocker covers.
Ask me how I know.
I got rid of the whole setup with umbrellas that fail due to heat in the heads and hoses dangling. Put in solid bolts, drilled and tapped a hole in the cam cover for a 90° fitting and used the Hayden Krankvent kvp38 for a better one way valve. Much better setup. My motor even idled noticeably better with the pistons not fighting all that positive pressure on the downstroke.
Otherwise pull the rocker covers and replace the umbrella valves. They don't last forever.
Ask me how I know.
I got rid of the whole setup with umbrellas that fail due to heat in the heads and hoses dangling. Put in solid bolts, drilled and tapped a hole in the cam cover for a 90° fitting and used the Hayden Krankvent kvp38 for a better one way valve. Much better setup. My motor even idled noticeably better with the pistons not fighting all that positive pressure on the downstroke.
Otherwise pull the rocker covers and replace the umbrella valves. They don't last forever.
Last edited by 60Gunner; Nov 5, 2019 at 04:07 PM.
Seasoned HDF Member
Joined: Aug 2017
Posts: 7,539
Likes: 12,183
From: Indianapolis
Umbrellas valves bad and allowing air to be sucked back in. Too much crankcase pressure builds and results in gasket leaks. Especially rocker covers.
Ask me how I know.
I got rid of the whole setup with umbrellas that fail due to heat in the heads and hoses dangling. Put in solid bolts, drilled and tapped a hole in the cam cover for a 90° fitting and used the Hayden Krankvent kvp38 for a better one way valve. Much better setup. My motor even idled noticeably better with the pistons not fighting all that positive pressure on the downstroke.
Otherwise pull the rocker covers and replace the umbrella valves. They don't last forever.
Ask me how I know.
I got rid of the whole setup with umbrellas that fail due to heat in the heads and hoses dangling. Put in solid bolts, drilled and tapped a hole in the cam cover for a 90° fitting and used the Hayden Krankvent kvp38 for a better one way valve. Much better setup. My motor even idled noticeably better with the pistons not fighting all that positive pressure on the downstroke.
Otherwise pull the rocker covers and replace the umbrella valves. They don't last forever.
Grand HDF Member
Joined: Sep 2017
Posts: 4,359
Likes: 1,219
From: Dubuque, IA
I've since replaced the brass 90° fitting with a chrome one I had laying around. Its a 1/8 npt to hose barb. I've also shortened the hose to the krankvent to about 5" and added an exit hose to under the frame ending under the crossover pipe keeping a slight downward angle. No filter . They just clog up.
Much better one way valve. Comes apart for cleaning if necessary.
Here's a pic of the krankvent opened up. It uses the same umbrella that's replaceable but has no slop in it and it's not going to warp from heat.
There's a detailed how to write up in the Sportsterpedia at the xlforums.
Much better one way valve. Comes apart for cleaning if necessary.
Here's a pic of the krankvent opened up. It uses the same umbrella that's replaceable but has no slop in it and it's not going to warp from heat.
There's a detailed how to write up in the Sportsterpedia at the xlforums.
Last edited by 60Gunner; Nov 5, 2019 at 04:40 PM.
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