Differences

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--- techtalk:ih:oil03p [2021/11/11 18:51]
hippysmack
+++ techtalk:ih:oil03p [2021/11/11 21:26]
hippysmack [Inspect both gerotor sets]
@@ Line 87: / Line 87: @@
   * Elongated scratches in these pads allow a constant amount of generated pressure on the outlet side to squirt back to the inlet side of the pump. \\ This will lower the pressure to the extent of how deep the scratches are. \\ Deep scratches allow more oil pressure or oil flow to recirculate from the outlet back to the inlet within the oil pump. \\ This makes for less oil gauge pressure on the feed side as well as less oil flow to the motor. \\ This makes for less oil flow back to the oil tank.
   * How many scratches or how deep the scratches need to be before the pump housing/cover needs to be replaced has never been publicized by the MoCo. \\ They apparently didn't want to get into the weeds... as I've done here.
-  * Backpressure is greater on the feed side than it is the return side. \\ The feed path from the pump has many turns and restrictions that build pressure. \\ Since oil is not compressible, it can't absorb any of that pressure. \\ So excess pressure is sent backwards from the restrictions. \\ This is how oil can recirculate form the feed outlet back to the feed inlet through out of service clearances and oil pump pad wear. \\ When the pressure is reverted backward, it runs back to the inlet side of the pump. \\ If backpressure is allowed to constantly run back to the inlet side, it will send oil back up the feed hose. \\ If you normally would have say 4psi at idle on the pump outlet, you'd now have 2 psi on the outlet and 2 psi going back to the inlet.
+  * Backpressure is greater on the feed side than it is the return side. \\ The feed path from the pump has many turns and restrictions that build pressure. \\ Since oil is not compressible, it can't absorb any of that pressure. \\ So excess pressure is sent backwards from the restrictions. \\ This is how oil can recirculate from the feed outlet back to the feed inlet through out of service clearances and oil pump pad wear. \\ When the pressure is reverted backward, it runs back to the inlet side of the pump. \\ If backpressure is allowed to constantly run back to the inlet side, it will send oil back up the feed hose. \\ If you normally would have say 4psi at idle on the pump outlet, you'd now have 2 psi on the outlet and 2 psi going back to the inlet.
   * Consequently, more oil will recirculate thru the feed side than the return side if both big pads have identical width and depth elongated scratches. \\ The backpressure from the feed side would push more oil faster under the gerotors than the return side with less backpressure. \\ If the oil tank vent line is stopped up, backpressure on the return side of the pump will be greater and send more oil under the gerotors back to the sump.
   * I'd guesstimate that there are a whole lot of Sportsters on the road with motors having gerotor pumps with various degrees of scratches. \\ The fact that there hasn't been a lot of talk on degrees of scratches in the oil pump says that most probably don't worry too much about them. \\ But then, you end up seeing that one complete teardown due to an oil pump problem and you get to wondering yourself.
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   * The gerotors are much taller than the pin thickness.
   * So the height of the slot allows a fudge factor on quick throttle blips and the gerotors won't be affected. \\ The gearshaft will rise some on higher throttle and there is built in "up and down" clearance in the pump to allow this. \\
-  * The pins are not pressed into the gearshaft and the holes in the gearshaft for the pins are different depths on several used gearshafts inspected. \\ Knowing this, it makes sense to be aware that the holes in the shaft can wallow out or the loose fit of the pins can wear the pins faster. \\ You can buy a handful of new pins only to find they are all different dims as well. \\ If you find real slop in the pin fit to the pins, either replace the pins and/or the gearshaft. \\ Do not buy hardened pins as that will defeat the purpose of the "shear pin" design. If the pins only protrude slightly into the gerotor slots, use longer pins. \\
+  * The pins are not pressed into the gearshaft and the holes in the gearshaft for the pins are different depths on several used gearshafts inspected. \\ Knowing this, it makes sense to be aware that the holes in the shaft can wallow out or the loose fit of the pins can wear the pins faster. \\ You can buy a handful of new pins only to find they are all different dims as well. \\ If you find real slop in the pin fit to the gearshaft, either replace the pins and/or the gearshaft. \\ Do not buy hardened pins as that will defeat the purpose of the "shear pin" design. If the pins only protrude slightly into the gerotor slots, use longer pins. \\
 The pics below are used parts but show the pin locations and how they look installed with a gerotor on the shaft. \\
@@ Line 153: / Line 153: @@
 {{:techtalk:ih:oil:1977-1985_oil_pump_gearshaft_pins_by_hippysmack.jpg?direct&300|}} {{:techtalk:ih:oil:77-85_oil_pump_gearshaft_pin_location_3_by_hippysmack.jpg?direct&300|}} {{:techtalk:ih:oil:77-85_oil_pump_gearshaft_pin_location_5_by_hippysmack.jpg?direct&300|}} \\
 ===== Inspect both gerotor sets =====
@@ Line 179: / Line 178: @@
 **Check inner to outer gerotor clearance on each gerotor set**. \\
 Each gerotor set is made with an inner and outer piece. Mesh the two pieces together (as they normally would sit in operation). \\
+This clearance has a direct relationship to oil pump flow and oil pressure. \\
+The wider the clearance the more the gerotors lose their ability to hold enough pressure to the outlet cavity. \\
+They also the ability to transfer oil from the feed cavity back to the inlet cavity and recirculate oil within the oil pump. \\
   * Arrange so there is 1 inner tooth facing the center of the wide outer radius. \\ Use a feeler gauge between the inner tooth and outer radius there for a maximum of .004" clearance between them. \\ If the clearance is larger than .004", replace the affected gearotor set. Repeat for the other gerotor set.
 {{:techtalk:ih:oil:1977-1985_oil_pump_gerotors_-_checking_clearance_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) \\
 \\
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 ===== Inspect the oil check valve =====
 [[techtalk:ih:oil01#oil_pump_check_valve|Click Here]] to read more about the oil pump check valve in the Sportsterpedia. \\
@@ Line 210: / Line 215: @@
 {{:techtalk:ih:oil:77-85_oil_check_valve_1_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:ih:oil:77-85_oil_check_valve_drawing_by_hippysmack.jpg?direct&300|}} ((photo by Hippysmack)) {{:techtalk:ih:oil:1977-1985_oil_pump_check_valve_by_screwloose.jpg?direct&300|}} ((photo by Screwloose of the XLFORUM http://xlforum.net/forums/showthread.php?t=1979566)) \\
 ===== Inspect the spring washer =====