Differences

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--- techtalk:evo:engmech07 [2021/06/19 00:05]
hippysmack [Buell (XB type) Breather Valve]
+++ techtalk:evo:engmech07 [2022/05/12 18:35]
hippysmack [Blowing through the vent]
@@ Line 62: / Line 62: @@
 |{{:techtalk:evo:oil:89_cam_cover_1_by_bryan350.jpg?direct&250|}}|{{:techtalk:evo:oil:89_cam_cover_2_by_bryan350.jpg?direct&250|}}|{{:techtalk:evo:oil:89_cam_cover_3_by_bryan350.jpg?direct&250|}}|
 |  89 cam cover with breather baffle tube attached (it should be tight but still pull out) ((photos by Bryan350 of the XLFORUM http://xlforum.net/forums/showthread.php?t=1712011))  |||
-**Testing the L84-90 umbrella valve**: \\
-A working valve should help reduce oil mist. ((Four Speed of the XLFORUM http://xlforum.net/forums/showthread.php?p=5745528#post5745528)) \\
-Since it's a one-way valve, air goes out but doesn't come back in. \\
-To make sure the umbrella valve is still working; \\
-Before you position the hose, use a bit of clean pipe and blow gently through the breather. \\
-It should close the valve and stop air flow.
-You may have to find an aftermarket replacement if the valve is shot as OEM replacements are hard to come by now. \\
-The 5 speed ones do not fit.
 ====== 1991-2003 Sportster Breather Valve ======
@@ Line 81: / Line 71: @@
   * In 1991, along with the 5-speed transmission, the MoCo moved the crankcase breathing from the cam box cover outlet to breather bolts in the heads.  \\ Previously, these bolts were just used to mount the carb and air cleaner to the heads.
-  * The new breather system uses (2) one-way umbrella valves placed in the rocker boxes (1 each placed on the intake side). \\ These expel crankcase vapors through vents in the top of the cylinder head and into the carb to be burnt. ((FoxsterUK of the XLFORUM  http://xlforum.net/forums/showthread.php?t=518948&highlight=wet+sumping))
+  * The new breather system uses (2) one-way umbrella valves (26856-89) placed in the rocker boxes (1 each placed on the intake side). \\ The part number was later updated to (26856-89A). \\ These expel crankcase vapors through vents in the top of the cylinder head and into the carb to be burnt. ((FoxsterUK of the XLFORUM  http://xlforum.net/forums/showthread.php?t=518948&highlight=wet+sumping))
     * On each piston downstroke, crankcase pressure (air and oil mist) is routed up the pushrod tubes into the rocker box (bypassing the falling oil from the rocker boxes).
     * Collected air pressure and oil mist in each rocker box is routed up into a sealed cavity in the lower portion of the box.
@@ Line 202: / Line 192: @@
 {{:techtalk:evo:engmech:cometic_gasket_1_by_dieselvette.jpg?direct&300|}} ((photo by dieselvette of the XLFORUM http://xlforum.net/forums/showthread.php?p=5769573#post5769573)) {{:techtalk:evo:engmech:cometic_gasket_2_by_dieselvette.jpg?direct&300|}} ((photo by dieselvette of the XLFORUM http://xlforum.net/forums/showthread.php?p=5769573#post5769573))
 ====== Head Breather Bolts ======
@@ Line 240: / Line 231: @@
 Or it contributes to too high of oil density and slings excess oil out. \\
 Other factors are involved so results will vary. \\
+====== Breather Valve Testing ======
+[[techtalk:ref:engmech04#crankcase_pressure_testing|Click Here]] for information on testing crankcase pressure in the Sportsterpedia. \\
+There are no service intervals for the breather valve(s) in the FSMs. Also, there is no method of testing them in the FSMs. \\
+But when they harden over time, you might experience more oil vapor, oil droplets or oil puking out the breather vent(s). \\
+The air coming out the vent(s) pulses according to piston position. \\
+On upstroke, a low pressure is created in the bottom end. On downstroke, positive air pressure is created by piston downstroke. \\
+It's never a bad idea to replace the breather valves if you have any question whether you have a bad one. \\
+From the pics, it looks like the front breather unit is stopped up.
+-1990 Sportsters have one umbrella in the breather baffle tube inside the cam cover. \\
+-2003 Sportsters have (2) umbrellas (one in each rocker box). \\
+-up Sportsters have (2) umbrellas (one in each rocker box inside a sealed plastic breather unit). \\
+The 2004 breather units have a removable fiber mesh filter under the umbrella that can stop up with gunked oil. \\
+The mesh disc in the unit can get oil soaked and not pass any air through the umbrella. \\
+The oil on the soaked mesh can vapor off if it doesn't cool on shutdown and gunk up there. If it gunks up, the mesh should be pulled and cleaned or replaced. \\
+===== Test for air flow at the vent =====
+You can verify a stopped up breather valve by "feeling" for air moving from the breather vent(s) with the air cleaner off, finger near each vent. \\
+As long as you have know air is moving, then the breather valve isn't stopped up. \\
+That doesn't mean it's working properly though. \\
+It's hard to tell by feel alone if air is moving out or if air is moving in. \\
+But there is a point where you may FEEL both air out and air in at the fingertip near the vent(s). \\
+If there are any questions about the umbrella valves / units working properly, you could just replace them and be done with it. \\
+With the rubber umbrellas hardening over time, there is nothing lost by replacing them. \\
+However, with the air cleaner off and a finger placed into the vent air stream; \\
+  * The exiting air from the vent is being sped up from the umbrella chamber to the vent. \\ This will pressurize the exit vent, hence the "FEEL" of pressure. ((bustert of the XLFORUM http://xlforum.net/forums/showthread.php?t=2081302)) \\ When the flow stops abruptly (pulse finishes), there is an instant void that is filled with atmospheric pressure. \\ Hence the "FEEL" of return flow.
+  * A new flexible umbrella is designed to allow pressure to move out, not in. \\ However, outside air can still enter through the oil drain back hole on engine vacuum cycles.
+  * 1986-up breather valves also incorporate an oil drain back hole for engine vacuum to pull separated oil from mist back into the motor. \\ The drain hole is past the umbrella between it and the outlet air vent. The drain hole is not controlled by the umbrella but rather engine vacuum. \\ So after the drain hole empties separated oil and is still under vacuum at that split second, holding a finger to the vent may feel a slight vacuum.
+  * If an umbrella is stiff and not closing fully, you may FEEL air both push and pull at the breather vent. \\ The umbrella has a loose clearance under it. \\ It has a stem that pops into a hole in it's resting place and the stem is slightly longer than the hole is deep. \\ If an umbrella hardens, it will do so after cooling down, engine shut off. \\ So it will harden in it's flat position. \\ On startup, positive air pressure (and oil mist) will still get under and by the affected umbrella, just not as well as if it were flexible. \\ So at it's vent, you may feel less air pressure due to a partially opening breather valve.
+  * The faster RPM, the faster the breather "umbrella" acts (flexing closed on upstroke and open on downstroke). \\ If the rubber umbrella hardens over time, it may not be able to act as fast as the pistons. \\ So you may "feel" both pressure and vacuum at the vent with your finger tip, air cleaner removed.
+{{:techtalk:evo:engmech:2004-up_breather_vent_-_feeling_air_movement_by_hippysmack.png?direct&500|}} ((drawing by Hippysmack)) \\
+There is an overlap on the bottom stroke cycle where the rear piston is at the bottom of it's stroke and the front piston is still coming down. \\
+Next, the rear piston rises creating a partial lowering of air pressure under the front piston. \\
+Full vacuum is not created until both pistons are on their up stroke. \\
+So there is a lull area in each cycle that can be perceived as both pressure and suction at the breather vent even with good working umbrellas. \\
+{{:techtalk:evo:engmech:2004-up_breather_vent_-_how_air_vacuum_closes_it_by_hippysmack.png?direct&500|}} ((drawing by Hippysmack)) \\
+===== Blow testing through the vent =====
+Since it's a one-way valve, air should go out but not come back in (past the umbrella itself). \\
+Before you position the hose, you can use a bit of clean pipe and blow gently through the breather. ((Four Speed of the XLFORUM http://xlforum.net/forums/showthread.php?p=5745528#post5745528)) \\
+It should close the valve and stop air flow (if you use a quick hard breath). \\
+However, blowing slow and gently will allow a small amount of breath to go into the engine through the tiny oil drainback hole. \\
+You may have to find an aftermarket replacement if the valve is shot and OEM replacements are hard to come by. \\
+The 5 speed (rocker box) umbrellas are smaller than the 4 speed (cam cover) umbrellas and these won't interchange. \\
 \\

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