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techtalk:ref:engmech04 [2019/08/13 17:28]
hippysmack [Head Vents vs Cam Chest Vent]
techtalk:ref:engmech04 [2019/11/14 03:35] (current)
hippysmack [Head Vents vs Cam Chest Vent]
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 {{:​techtalk:​ref:​engmech:​86-90_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​86-90_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​86-90_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​86-90_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack))
  
-91-03 models with head breather vents: \\ +91-97 models with head breather vents: \\ 
-{{:​techtalk:​ref:​engmech:​91-03_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ​((drawing by Hippysmack)) ​{{:​techtalk:​ref:​engmech:​91-03_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ​((drawing by Hippysmack))+{{:​techtalk:​ref:​engmech:​91-97_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} {{:​techtalk:​ref:​engmech:​91-97_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} \\ 
 + 
 +98-03 models with head breather vents: \\ 
 +{{:​techtalk:​ref:​engmech:​98-03_sportster_positive_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} {{:​techtalk:​ref:​engmech:​98-03_sportster_negative_crankcase_pressure_by_hippysmack.jpg?​direct&​300|}} ​\\
  
 04 and Up models with head breather vents: \\ 04 and Up models with head breather vents: \\
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 ===== Blowby ===== ===== Blowby =====
 Blowby pertains to the condition of ring seal at the cylinders / pistons. \\ Blowby pertains to the condition of ring seal at the cylinders / pistons. \\
 +Combustion above the piston is pushed past the rings and into the crankcase. \\
 It is fundamentally just exhaust that went past the rings instead of out the exhaust port. ((aswracing oftheXLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1946516&​page=4)) \\ It is fundamentally just exhaust that went past the rings instead of out the exhaust port. ((aswracing oftheXLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1946516&​page=4)) \\
 It's depleted of oxygen, it's hot, and it picks up moisture and oil in it's travels through the crankcase and into your intake tract. \\ It's depleted of oxygen, it's hot, and it picks up moisture and oil in it's travels through the crankcase and into your intake tract. \\
 So it's displacing oxygen in the intake charge (through the air cleaner) that would otherwise contribute to combustion. \\ So it's displacing oxygen in the intake charge (through the air cleaner) that would otherwise contribute to combustion. \\
-It also heats the intake charge which contributes to detonation. \\ +It also heats the intake charge ​when the breather vent is piped back to the air cleaner ​which contributes to detonation. \\ 
-It's just a bad thing all the way around, robbing power, causing detonation, and contributing to carbon build-up. It's well worth it to remove it from the intake tract and vent it to the atmosphere or exhaust instead, in my opinion.+It's just a bad thing all the way around, robbing power, causing detonation, and contributing to carbon build-up. ​\\ 
 +It's well worth it to remove it from the intake tract and vent it to the atmosphere or exhaust instead. ​\\
  
-Combustion above the piston is pushed past the rings and into the crankcase. \\ 
 What actually 'blows by' the rings and into the crankcase is a mix of unburnt fuel, water, soot, acids etc. ((bunny32 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=67658&​page=2)) \\ What actually 'blows by' the rings and into the crankcase is a mix of unburnt fuel, water, soot, acids etc. ((bunny32 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=67658&​page=2)) \\
  
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 First, a little background. \\ First, a little background. \\
 In the stock configuration,​ the crankcase vents through a pair of "​umbrella"​ valves, which are essentially check valves. \\ In the stock configuration,​ the crankcase vents through a pair of "​umbrella"​ valves, which are essentially check valves. \\
-There is no air inlet into the motor. \\ +There is a slight ​air inlet into the motor from a tiny hole near the umbrella((Hippysmack)) ​\\ 
-The pistons come down the first time and the crankcase air is expelledthe air is forced out through the umbrella valves. \\+It acts as both an oil drain for anything that gets past the umbrella and an air intake to keep negative pressure from getting too high.  
 +The pistons come down the first time and the crankcase air is expelled ​with the air being forced out through the umbrella valves. \\
  
 But when the pistons go back up, the umbrella valves block the inflow of air, causing a slight vacuum in the crankcase. \\ But when the pistons go back up, the umbrella valves block the inflow of air, causing a slight vacuum in the crankcase. \\
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 Properly functioning umbrella valves therefore serve the purpose of significantly reducing the breather capacity requirement while also minimizing crankcase pressure. \\ Properly functioning umbrella valves therefore serve the purpose of significantly reducing the breather capacity requirement while also minimizing crankcase pressure. \\
-Excessive airflow & oil discharge through the breathers can be caused by malfunctioning umbrella valves that are allowing air into the motor. \\+Excessive airflow & oil discharge through the breathers can be caused by malfunctioning umbrella valves that are allowing ​more air into the motor. \\
  
 For this test, an additional vent was added at the timing plug hole. \\ For this test, an additional vent was added at the timing plug hole. \\
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 ===== Testing with a Slack Tube by bustert ===== ===== Testing with a Slack Tube by bustert =====
 +==== Sub Documents ====
 +  * [[techtalk:​ref:​engmech04e|Building Your Own Slack Tube]]
 +  * [[techtalk:​ref:​engmech04f|Using / Diagnosing with a Manometer Slack Tube]]
 +  * [[techtalk:​ref:​engmech04g|Slack tube testing on a 1998 1250S model]]
  
 Testing was done from the timing plug hole and then from the oil tank with a slack tube on a 2001 XL1200S (with no load) by bustert of the XLFORUM. ((http://​xlforum.net/​forums/​showthread.php?​p=5767694#​post5767694)) \\ Testing was done from the timing plug hole and then from the oil tank with a slack tube on a 2001 XL1200S (with no load) by bustert of the XLFORUM. ((http://​xlforum.net/​forums/​showthread.php?​p=5767694#​post5767694)) \\
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 The testing showed that the test bike acted as intended with head breathers (venting through lines bypassing the A/C to atmosphere). \\ The testing showed that the test bike acted as intended with head breathers (venting through lines bypassing the A/C to atmosphere). \\
 +
 +===== Testing Notes =====
 +Each of the tests above do basically support each other given the different variables. \\
 +But the results have to be taken in context as each have different criteria for testing. \\
 +
 +  * **Testing from DK Custom**:
 +    * The criteria for their testing was to see how much air was passed out the breather vents (outside the engine) at idle, under a load, at cruising speeds and on throttle let-off'​ for different model engines. They sell modified breather venting configurations and was doing some R&D presumably in the interest of same.
 +    * Their testing supports bustert'​s slack tube testing as normally at most of the RPM range, there is more vacuum than positive pressure. And it's the positive pressure that leaves the engine. Therefore, their results for the Sportster are equaled out more. Even though there is normal blowby throughout the RPM range, the vacuum created buffers that.
 +    * In example, 15" of vacuum at idle that all of a sudden is hit by 5" of positive pressure rolling the throttle still yields 10" of vacuum at the time. So there would be no air moving into the balloon or container at that point. In theory and during that transition from 15" to 10" vacuum, more oil is pushed toward the scavenge hole in the sump, the pump gets a fatter supply of oil to send to the tank, pressure goes up in the air space in the tank due to the restriction size of the vent.
 +
 +  * **Testing from bustert**:
 +    * This was a test of the differential pressure changes (inside the engine) through the RPM range up to 6000 RPM.
 +    * You may have read and heard from many sources that the Sportster requires a '​slight vacuum'​. But the slack tube testing puts a visual to the process showing that the '​slight vacuum'​ is not really a stagnant number but a constantly moving range.
 +
 +  * **Testing from aswracing**:​
 +    * Dyno testing was with the normal head breather vents in place (with and without the timing hole plug removed) to see if either would show increased HP over the other. \\ The dyno sheets show the affects (HP changes) between the stock setup and with addition of air induced into the engine through the RPM range. \\ However, it does not show internal pressures during the testing.
 +    * The testing revealed a dip in performance starting around 5700 RPM which coincides with bustert'​s slack tube testing showing positive and negative pressure equaling out up in that range. But the Dyno test is a load test as where the slack tube was done with no load on the engine... more variables.
 +
 +**What does all this mean**? \\
 +
 +The testing shows that there is more potential for crankcase pressure problems in the high RPM range. \\
 +It also shows that Sportster engine breathing was designed for peaks in the upper range but not for sustained use there. \\
 +There will be a normal amount of air passing the rings by design. \\
 +As the rings heat up and expand, there will be less air passed by them until you run up into the 5000 RPM range. ​ \\
 +Then, the rings will flutter and pass more combustion air into the crankcase which creates more positive pressure in the crankcase. \\
 +Normal blowby increases with engine speed. \\
 +Couple that with the increasing speed of the pistons which helps to equalize positive and negative pressure during operation. \\
 +As engine speed increases, there is not as much time to build vacuum on upstroke or positive pressure on downstroke due to the faster changing piston positions. \\
 +Just as you can inhale air slowly and fill up your lungs but faster breathing will not allow you to fill them due to the faster time that you exhale. \\
 +This would make for a shorter range of (both vacuum and positive) pressure that would be able to build in the crankcase. \\
 +So the internal pressure is more stable until extra air (blowby from ring flutter or other) is induced into the crankcase. \\
 +
 +**What causes extra air in the crankcase**?​ \\
 +
 +Ring flutter around 5000 RPM and higher is thought of as the main culprit on a healthy engine. \\
 +Gasket / air leaks react the same as ring flutter but at a lower RPM. \\
 +They allow more air into the engine that add to the positive and take away some of the negative (vacuum). \\
 +So the introduction of air leaks into the crankcase lowers the RPM at which pressure changes affect the system. \\  ​
 +Worn / stiff breather valves that do not fully close will allow more air at atmosphere into the crankcase. \\
 +This lowers the vacuum and contributes to higher positive pressure on downstroke changing the ratio at a lower RPM. \\
 +The timing of the breather valve opening and closing can also bring in air to the crankcase during upstroke. \\
 +Guess we could call that umbrella flutter. \\
 +The faster it closes, the more vacuum is kept in the crankcase on upstroke. \\
 +The slower it closes, the more air is allowed to enter and lower residual vacuum. \\
 +
 +**Why is the ratio of positive and negative pressure important**?​ \\
 +
 +It takes a balance of the two to run a Sportster engine. \\
 +
 +Piston upstroke creates negative pressure and suction of oil from the sump. \\
 +It pulls oil up in the form of oil mist to be tossed around on the moving metal parts. \\
 +So it is important for lubrication and it keeps down aeration in the oil. \\
 +But without the reciprocating piston downstroke, there wouldn'​t be a lot of force to help splash it around other than the spinning wheels. \\
 +The upstroke pulls oil into suspension (air/oil mist) so the downstroke can help blow the mist around working in conjunction with flywheel and cam rotation. \\
 +Negative pressure is also important for ring seal as it allows the rings to fully seat on the bottom of the ringlands during upstroke decreasing blowby. \\
 +Too much negative pressure is detrimental to oil scavenging as it allows more oil to be pulled up into suspension instead of moving toward the scavenge port in the sump. \\
 +The bulk of gravity oil on the sump floor is heavier than the moving air. \\
 +But the spinning action of the flywheels can pull that oil up to be slung around the wheels creating more drag as it does. \\
 +So it's important to get the excess oil in the bottom out of the engine as fast as possible to keep down flywheel drag. \\
 +That's where the positive pressure comes in. \\
 +
 +Positive pressure is important for oil scavenging as it works in conjunction with splash lubrication as well as the suction of the oil pump. \\
 +The positive pressure generated by the downstroke pushes oil toward the scavenge pump to be sucked vertically into the oil passage to the pump. \\
 +So there is a balance of positive and negative pressure that has to be maintained for overall engine operation. \\
 +
 +The role of positive and negative pressure can be confusing. \\
 +Even though there is a positive '​push'​ on internal pressure through piston downstroke, the overall internal pressure is still negative. \\
 +It's just less negative than it was before the downstroke. This creates a pulsing effect on oil in the sump which helps shift the oil toward the scavenge port. \\
 +Even though there is normal blowby throughout the RPM range, the vacuum created buffers that. \\
  
  
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 |{{:​techtalk:​ref:​engmech:​86-90_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​91_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}| |{{:​techtalk:​ref:​engmech:​86-90_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​91_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|
  
-|  92-03 engine breathing paths. ((drawing by Hippysmack)) ​ |  04 and Up engine breathing paths. ((drawing by Hippysmack)) ​ | +|  92-97 engine breathing paths. ((drawing by Hippysmack)) ​ |  98-03 engine breathing paths. ((drawing by Hippysmack)) ​ |  04 and up engine breathing paths. ((drawing by Hippysmack)) ​ | 
-|{{:techtalk:​ref:​engmech:​92-03_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​04_and_up_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}| +|{{techtalk:​ref:​engmech:​92-97_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|{{techtalk:ref:​engmech:​98-03_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|{{techtalk:​ref:​engmech:​04_and_up_sportster_engine_breathing_by_hippysmack.jpg?​direct&​300|}}|
  
 |  Testing CC pressure on the dyno. ((photo by Jörgen http://​xlforum.net/​forums/​showthread.php?​t=75740&​page=9)) ​ | |  Testing CC pressure on the dyno. ((photo by Jörgen http://​xlforum.net/​forums/​showthread.php?​t=75740&​page=9)) ​ |
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 Wet sumping is only one potential problem you may encounter with them. ((maru of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=3780510#​post3780510)) \\ Wet sumping is only one potential problem you may encounter with them. ((maru of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=3780510#​post3780510)) \\
 In the right application they can not be beat but you better have your ducks in a row. \\ In the right application they can not be beat but you better have your ducks in a row. \\
 +
 +**Buell crankcase breathing**:​ \\
 +|  This is a Buell XBRR with reed valves through the cam chest wall. ((photos by aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=829935)) ​ ||
 +|{{:​techtalk:​ref:​engmech:​reed_valves_1_on_buell_xbrr_by_aswracing.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​reed_valves_2_on_buell_xbrr_by_aswracing.jpg?​direct&​300|}}|
 +
  
 ===== Why Oil Pukes Out the Air Cleaner ===== ===== Why Oil Pukes Out the Air Cleaner =====
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 So to keep oil out of the A/C, means keeping engine breathing And wet sumping in balance. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5757523#​post5757523)) \\ So to keep oil out of the A/C, means keeping engine breathing And wet sumping in balance. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5757523#​post5757523)) \\
 +
 +===== Breather Catch Can Test For Oil Leaks Out the Vent  =====
 +A test was done by XLFORUM member cjburr. Test apparatus and results are below. ((cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=13)) \\
 +This testing was done to help diagnose an oil leak that couldn'​t be seen or otherwise detected. \\
 +However, this may be a good exercise if you are concerned about how much oil you may be losing from the crankcase puking. \\
 +It should show what, how much and when oil accumulates in the hose / catch can. \\
 +The length / size of tubing will change crankcase pressure to an extent so the results may not reflect exactly what's going on inside your engine. \\
 +
 +The vent to air cleaner was inspected and then removed for testing. The factory system routes the breathers to the front of the carb. \\
 +There was no evidence of the amount of oil that was being lost in the intake tract. \\
 +With the Forcewinder A/C removed, there was no evidence of oil.
 +A homemade catch can with a vent hole and a clear tube was installed to inspect while riding. \\
 +
 +|  A/C removed. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=13)) ​ ||  Homemade catch can. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=13)) ​ |
 +|{{:​techtalk:​ref:​engmech:​breather_catch_can_test_1_by_cjburr.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​breather_catch_can_test_2_by_cjburr.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​breather_catch_can_test_3_by_cjburr.jpg?​direct&​300|}}|
 +
 +The A/C was re-installed with the venting ran to the catch can. \\
 +The oil tank was filled to just under half way up the stick with SYN3. \\
 +The bike was ridden hard (10 miles of city driving then 50 miles of elevated speeds). \\
 +RPM was ran up to 6000 in 5th (8 times) and up to 100 MPH for 2 miles twice. \\
 +Total miles run were 75 and all but 20 miles of that were at 80 MPH or more. \\
 +The only thing that showed up in the tube running to the catch can was just some moisture but no oil. \\
 +|  The catch can was clean but 1/4 quart of oil had been lost as viewed from the dipstick. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=13)) ​ |||
 +|{{:​techtalk:​ref:​engmech:​breather_catch_can_test_4_by_cjburr.jpg?​direct&​300|}}| {{:​techtalk:​ref:​engmech:​breather_catch_can_test_5_by_cjburr.jpg?​direct&​300|}}|{{:​techtalk:​ref:​engmech:​breather_catch_can_test_6_by_cjburr.jpg?​direct&​200|}}|
 +
 +
  
 ===== Breather Valves ===== ===== Breather Valves =====
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 **Late 1982-Early 1984 models**: \\ **Late 1982-Early 1984 models**: \\
- The internal crankcase breather valve was redesigned to incorporate a rubber umbrella valve attached to the base plate along with a larger diameter (1-3/4” O.D.) oil separator washer on the generator armature. ((HD Service Bulletin #M-848 dated April 9, 1982))+The internal crankcase breather valve was redesigned to incorporate a rubber umbrella valve. \\ 
 +This is attached to the base plate along with a larger diameter (1-3/4” O.D.) oil separator washer on the generator armature. ((HD Service Bulletin #M-848 dated April 9, 1982)) ​\\
  
 **Late 1984-1990 models**: \\ **Late 1984-1990 models**: \\
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 ** 2004-Present**:​ \\ ** 2004-Present**:​ \\
 In 2004 the MoCo made some changes to the umbrella valve configuration. \\  In 2004 the MoCo made some changes to the umbrella valve configuration. \\ 
-The umbrella was retained but now inside a plastic housing with a pre-umbrella oil separating screen. \\+The umbrella was retained but now inside a plastic housing with a pre-umbrella oil separating screen ​(fiber mesh). \\ 
 +On 03< models, the oil is actually separated by the umbrella. The umbrella doubles as a one way air valve. \\ 
 +On 04> models, the oil is separated first by the mesh below the umbrella which frees the umbrella to be more of a one way air valve. \\ 
 +There is an extra oil chamber between the in and out of the breather assembly. \\ 
 +So it could be said that the 04-up breather valve has 2 stage separation with a small hole in the middle chamber to drain what gets past the mesh. \\ 
 Each '​breather valve' is assembled into a plastic fitting that is sealed over the outlet hole in the lower rocker box to the head breather bolt. \\ Each '​breather valve' is assembled into a plastic fitting that is sealed over the outlet hole in the lower rocker box to the head breather bolt. \\
 The new breather valves were also accompanied with new style hollow air cleaner mounting bolts for the pressure to escape. \\ The new breather valves were also accompanied with new style hollow air cleaner mounting bolts for the pressure to escape. \\
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 This mixture passes up from underneath the breather unit. \\ This mixture passes up from underneath the breather unit. \\
 The oil is designed to separate from the air by hitting the underside of the screen / umbrella valve and dropping back down into the rocker box. \\ The oil is designed to separate from the air by hitting the underside of the screen / umbrella valve and dropping back down into the rocker box. \\
 +
 From there it is routed back to the lower end. \\ From there it is routed back to the lower end. \\
 Air pressure is designed to continue up past the breather unit and exit a hole in each head on the intake valve side. \\ Air pressure is designed to continue up past the breather unit and exit a hole in each head on the intake valve side. \\
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 {{:​techtalk:​ref:​engmech:​engine_breathing_thru_heads_vs_cam_chest_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack)) {{:​techtalk:​ref:​engmech:​engine_breathing_thru_heads_vs_cam_chest_by_hippysmack.jpg?​direct&​300|}} ((drawing by Hippysmack))
 +
 +==== 91-up Breather Bolts ====
 +
 +The MoCo manipulated crankcase pressure with the different size holes in the breather bolts. \\
 +The crankcase splash holes were restricted in 2000 to keep more pressure in the crankcase. \\
 +Then the holes in the wall was closed up in 2004 to accommodate the addition of piston jets to cool the pistons. \\
 +The piston squirters (feed pressure from the pump) added the same amount of oil into the crankcase at a faster rate. \\
 +But the scavenger gerotors were not redesigned larger until 2007 to remove the oil faster from the crankcase. \\
 +So on 04-06 models, they got the same scavenge return rate (as previous models without the added oil). \\
 +The holes in the 04 Up bolts are stepped. They are smaller on the head side as above but bigger on the A/C side. \\
 +First, that creates more of a restriction than 91-03 models. The restriction can do a couple things: \\
 +It will create more backpressure inside the engine until a stronger force is applied from inside. \\
 +That stronger force would be the air created on downstroke. In a perfect world, the downstroke won't be impeded so the force won't slow down. \\
 +The higher positive pressure assists in oil scavenging (the pressure inside builds a little more from that restriction). ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2073932&​page=9)) \\
 +But it only bottles up pressure on downstroke and only to a point. That little more positive pressure is an extra push on the lower end toward the sump scavenge port. \\
 +Another result would be air moving out at a faster rate thru the smaller hole. The smaller hole creates higher pressure. Higher pressure equates to faster flow. \\
 +
 +{{:​techtalk:​evo:​carb:​91-03_breather_bolts_1_by_hippysmack.jpg?​direct&​300|}} ((photo by Hippysmack)) {{:​techtalk:​evo:​engmech:​04_up_breather_bolt_2_by_folkie.jpg?​direct&​300|}} ((photo by Folkie of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5756327#​post5756327)) {{:​techtalk:​evo:​engmech:​04_up_breather_bolt_1_by_folkie.jpg?​direct&​300|}} ((photo by Folkie of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5756327#​post5756327)) \\
 +
  
 ==== Head Drainage ==== ==== Head Drainage ====
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 The oil feed to the top end is pressurized and the return is gravity fed. ((jrclark19 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) \\ The oil feed to the top end is pressurized and the return is gravity fed. ((jrclark19 of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) \\
 The drain for the top end is at least 2-3 times larger than the hole in the pushrods. \\ The drain for the top end is at least 2-3 times larger than the hole in the pushrods. \\
 +
 +It's been said that CC pressure moving up the pushrod tubes interferes with drain oil traveling down the tubes. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2073932&​page=2)) \\
 +However, drain oil mainly goes into the head / cylinder drain holes from the rocker arms spraying the valves. \\
 +And liquid oil is much heavier than air moving up the passage. \\
 +Separated oil from mist falls back into the tubes. But that oil is also pulled down on piston upstroke and air/mist once again goes up on piston downstroke. \\
 +The higher venting from the heads also gives any oil that may be being carried along with the gas time to "drop out". \\
 +(which returns the oil back to the cam chest vis the pushrod / lifter block drain holes via gravity) \\
 +Obviously, there is less time for oil to drop out of suspension while breathing out the cam chest instead. \\
 +
 +The slack tube testing shows there is a predominate vacuum in a running engine until after 5000-6000 RPM. \\
 +Any output pressure in the head venting system has to travel up through separate pushrod tube passages to get out of the engine. \\
 +Any separated oil gravity falling from the rocker arms would overpower the positive upward push of crankcase pressure until the oil hit bottom. \\
 +An exception would be in high sustained, high RPM where there is excess ring flutter adding to equalized pressure in the crankcase. \\
 +(as in racing conditions). \\
 +
 +
  
 ==== Testing the Head Drains ==== ==== Testing the Head Drains ====
Line 758: Line 908:
 Oil was introduced into the head with a with a turkey baster. \\ Oil was introduced into the head with a with a turkey baster. \\
 (which is probably a higher volume of oil than it normally sees from the splash oiling) \\ (which is probably a higher volume of oil than it normally sees from the splash oiling) \\
 +However, if the drains were plugged, oil would overfill to the point of spewing oil at the seams and submerge the seals. ((cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=33)) \\ 
  
 |  Head ready for testing. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ |  Oil poured in and draining. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ |Oil level at the intake valve when it starts to drain to \\ the exhaust side. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ | |  Head ready for testing. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ |  Oil poured in and draining. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ |Oil level at the intake valve when it starts to drain to \\ the exhaust side. ((photo by cjburr of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=53769&​highlight=valve+guide&​page=31)) ​ |
Line 794: Line 945:
 The scavenge inlet sees pressure but is isolated from the vacuum when the pistons go back up. \\ The scavenge inlet sees pressure but is isolated from the vacuum when the pistons go back up. \\
 </​blockquote>​ </​blockquote>​
 +
 +
 ====== Wetsumping ====== ====== Wetsumping ======
 Click to read the full article on [[techtalk:​ref:​oil10#​wet_sumping|wetsumping]] in the REF section of the Sportsterpedia. \\ Click to read the full article on [[techtalk:​ref:​oil10#​wet_sumping|wetsumping]] in the REF section of the Sportsterpedia. \\
 +See also the Sportsterpedia page on [[http://​www.sportsterpedia.com/​doku.php/​techtalk:​ref:​oil05|Engine and Primary Oil System Modifications]] \\
  
 Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing. \\ Wetsumping during shutdown periods is a condition of bad oil pump sealing, bad check valve or regulator (if equipped) sealing. \\
Line 1032: Line 1186:
  
 With the oil cap off the tank on a hot idling engine (so far rigid S models only), the engine speed can drop app. 1,000 RPM at 1050 idle. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5763694#​post5763694)) \\ With the oil cap off the tank on a hot idling engine (so far rigid S models only), the engine speed can drop app. 1,000 RPM at 1050 idle. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5763694#​post5763694)) \\
 +
 Another example with oil temp 210, raised idle to 1200 and lost 700 RPM. \\ Another example with oil temp 210, raised idle to 1200 and lost 700 RPM. \\
 So the exact power loss is variable but true. \\ So the exact power loss is variable but true. \\
Line 1040: Line 1195:
 The suspension fluid and return oil together in the line helps to separate the oil back out of suspension by the time it reaches the tank. \\ The suspension fluid and return oil together in the line helps to separate the oil back out of suspension by the time it reaches the tank. \\
 The bulk of air / oil mist is generated in the crankcase, not the cam chest where the vent line to the tank is. \\ The bulk of air / oil mist is generated in the crankcase, not the cam chest where the vent line to the tank is. \\
-(leaving what comes out the top of the oil tank to be nothing but air). \\+(leaving ​most of what comes out the top of the oil tank to be air). \\
 The higher air/oil density drags the flywheels and more oil is picked up in suspension with the engine breathing both in and out. \\ The higher air/oil density drags the flywheels and more oil is picked up in suspension with the engine breathing both in and out. \\
 The engine responds at idle from the higher load on the wheels. \\ The engine responds at idle from the higher load on the wheels. \\
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 Some potential air leak areas are in the pic below. \\ Some potential air leak areas are in the pic below. \\
 If these areas allow air to be pulled in the engine on upstroke, the added air will compound any other existing breathing problems. \\ If these areas allow air to be pulled in the engine on upstroke, the added air will compound any other existing breathing problems. \\
-{{:​techtalk:​ref:​engmech:​potential_cc_pressure_leaks_at_the_rocker_box_by_daggar_rider_labeled_by_hippysmack.jpg?​direct&​300|}} ((photo by dagger rider of the XLFORUM ))+{{:​techtalk:​ref:​engmech:​potential_cc_pressure_leaks_at_the_rocker_box_by_daggar_rider_labeled_by_hippysmack.jpg?​direct&​300|}} ((photo by dagger rider of the XLFORUM )) {{:​techtalk:​ref:​engmech:​bad_rocker_box_fiber_washer_by_hippysmack.jpg?​direct&​300|}} ((photo by Hippysmack)) \\
  
 ====== Vacuum Pump for Reducing Crankcase Pressure ====== ====== Vacuum Pump for Reducing Crankcase Pressure ======
 +Most of the information on the web involves the use of a vacuum pump on autos. \\ There'​s not much published on using them with motorcycle engines. \\
 +That doesn'​t mean anything other than speed shops may not want to divulge their secrets. Also big pumps are for big displacement autos. \\
 +You can use a vacuum pump that's too big for a Sportster engine and cause more harm than good. \\
 +They are used for compensation as well as for better ring seal, but mostly advertised for better ring seal. \\
 +There are pumps spec'd for vacuum measurements and also ones spec'd by RPM range. \\
 +But, along with the addition of a vacuum pump, there is also the addition of a performance multi-stage oil pump. \\
 +If you vented from the crankcase area: \\
 +
 +Splash is an important element in the sump area. Too much vacuum and you lose scavenge ability of the oil pump. \\
 +You may be able to tap into the side-top with a vent line and a reed valve. \\
 +The more the vacuum, even lower the positive will begin. \\
 +The rings act as a buffer between these two conditions as excess pressure could run both directions. \\
 +But positive pressure aides in oil scavenging. \\
 +So lowering positive pressure by default also hinders scavenging. \\
 +That's why racers with vacuum pumps use multistage scavenge pumps to account for the imbalance to scavenge and improve it. \\
 +
 +Regardless, it's evident that some racers use vacuum pumps to increase vacuum pressure in the crankcase of a Sportster engine. ((Hippysmack of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2073932)) \\
 +It's been said that positive crankcase pressure upon piston upstroke gets between the rings and basically causes bad sealing at the ringlands. \\
 +This is also in the high RPM range when ring flutter is present. So there are several things happening then. \\
 +But racers record higher power when using a vacuum pump. \\
 +However, it has also been said that inducing higher vacuum in a street engine may do more harm than good. Lower RPM may suffer from the imbalance. \\
 +
 A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. ((https://​www.gzmotorsports.com/​why-use-vacuum-pump.html)) \\ A vacuum pump, in general, is an added benefit to any engine that is high performance enough to create a significant amount of blow-by. ((https://​www.gzmotorsports.com/​why-use-vacuum-pump.html)) \\
 (that'​s high performance enough.... not worn enough) \\ (that'​s high performance enough.... not worn enough) \\
Line 1082: Line 1259:
   * Now add a vacuum pump with Z (-1) amount of pull. \\ Now you get X+1=Y-Z... seems the balance (to zero) is restored even though positive pressure is compiled of blowby. \\ But the lower the negative pressure is at the beginning of the downstroke, the lower the next positive pressure will be.   * Now add a vacuum pump with Z (-1) amount of pull. \\ Now you get X+1=Y-Z... seems the balance (to zero) is restored even though positive pressure is compiled of blowby. \\ But the lower the negative pressure is at the beginning of the downstroke, the lower the next positive pressure will be.
   * If you are generating 2 psi of positive pressure on downstroke but reduce it's beginning surge to -1 psi (Z), \\ the result will be only 1 psi of positive pressure during downstroke. \\ -1 (+) + 2 equals +1.   * If you are generating 2 psi of positive pressure on downstroke but reduce it's beginning surge to -1 psi (Z), \\ the result will be only 1 psi of positive pressure during downstroke. \\ -1 (+) + 2 equals +1.
- 
-The more the vacuum, even lower the positive will begin. \\ 
-The rings act as a buffer between these two conditions as excess pressure could run both directions. \\ 
-But positive pressure aides in oil scavenging. \\ 
-So lowering positive pressure by default also hinders scavenging. \\ 
-That's why racers with vacuum pumps use multistage scavenge pumps to account for the imbalance to scavenge and improve it. \\