29465-99 Breather Bolt
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Road Captain
Joined: Nov 2007
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29465-99 Breather Bolt
Good day; Riders.
This item is used on both cylinders and is placed within the air cleaner on my 2006 FLHTCUSE (touring) motorcycle.
I believe this to be a 1 way valve (output) into the air cleaner.
There is another opinion that says it's a 2 way valve which really doesn't make any sense to me.
Could somebody please provide a reasonable/understandable explanation to the operation of this valve and whether or not it is 1 or 2 way?
Thanks
This item is used on both cylinders and is placed within the air cleaner on my 2006 FLHTCUSE (touring) motorcycle.
I believe this to be a 1 way valve (output) into the air cleaner.
There is another opinion that says it's a 2 way valve which really doesn't make any sense to me.
Could somebody please provide a reasonable/understandable explanation to the operation of this valve and whether or not it is 1 or 2 way?
Thanks
Extreme HDF Member
Joined: Sep 2010
Posts: 14,744
Likes: 402
From: Phoenix '53, '88, '09 Big Twins
this is a type of bolt called a "banjo bolt"- they are used to connect fitting where fluid or gasses need to pass.
merely a bolt with a hole drilled up the stem, with a 90ş turn to the side so that flow is possible.
you already know that a piston moving up in the cylinder creates pressure- realize that when the piston is pushed back down the cylinder by expanding gasses ( combustion) pressure is built up in the crankcase by the backside of the piston coming down ...this needs to be vented.
up to about 1962, american cars just had a vent tube on the bottom of the motor "road draft" and that woul dspewk air and oil mist onto the road ( old black and white movies will always show the resulting streak of black in the center of the traffic lanes. polluting and dangerous, this was the first Federal auto emissions standard enacted- and we got the gasses vented to the intake of cars- usually with a PVC valve... since the heads are near the intake, easiest to vent the gasses there with a shorter hose and also the oil would tend to separate out from the oil and stay in the motor.
burning the oil mist is better than dumping it onto the road/atmosphere
there is a 1 way "umbrella" valve in the heads of big twins from 93 on.
imagine an umbrella where the fabric( rubber) is segmented and pressure from below will push the flaps up...pressure from above will just make them seal tighter.
so a 1 way valve.
umbrella valves can go bad with time temperature AND corruption of the oil ( vapour from unburned gas, weird magic addictive from the parts store etc)
a solid or non vented bolt in the heads will not allow the gasses to vent- and the pressure will push out gaskets or seals or worse
Mike
merely a bolt with a hole drilled up the stem, with a 90ş turn to the side so that flow is possible.
you already know that a piston moving up in the cylinder creates pressure- realize that when the piston is pushed back down the cylinder by expanding gasses ( combustion) pressure is built up in the crankcase by the backside of the piston coming down ...this needs to be vented.
up to about 1962, american cars just had a vent tube on the bottom of the motor "road draft" and that woul dspewk air and oil mist onto the road ( old black and white movies will always show the resulting streak of black in the center of the traffic lanes. polluting and dangerous, this was the first Federal auto emissions standard enacted- and we got the gasses vented to the intake of cars- usually with a PVC valve... since the heads are near the intake, easiest to vent the gasses there with a shorter hose and also the oil would tend to separate out from the oil and stay in the motor.
burning the oil mist is better than dumping it onto the road/atmosphere
there is a 1 way "umbrella" valve in the heads of big twins from 93 on.
imagine an umbrella where the fabric( rubber) is segmented and pressure from below will push the flaps up...pressure from above will just make them seal tighter.
so a 1 way valve.
umbrella valves can go bad with time temperature AND corruption of the oil ( vapour from unburned gas, weird magic addictive from the parts store etc)
a solid or non vented bolt in the heads will not allow the gasses to vent- and the pressure will push out gaskets or seals or worse
Mike
Last edited by mkguitar; May 26, 2016 at 05:08 PM.
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