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techtalk:ref:svcproc21 [2018/08/30 17:09] hippysmack [Dynamic Leakage (into the crankcase)] |
techtalk:ref:svcproc21 [2024/01/22 05:43] (current) hippysmack |
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| [[:techtalk:menu|{{ :techtalk:gototechnicalmenu.jpg|}}]] | [[:techtalk:menu|{{ :techtalk:gototechnicalmenu.jpg|}}]] | ||
| - | ====== REF: Troubleshooting - Engine - 04 ====== | + | ====== REF: Service Procedures 21 ====== |
| ====== Cylinder Leak-Down Test ====== | ====== Cylinder Leak-Down Test ====== | ||
| Line 11: | Line 11: | ||
| When an engine top end repair is needed, it's not always possible to determine if the repair can be made to only one cylinder or a complete top end teardown needs to be done. ((79-85 HD XL/XR FSM pg 3-10)) \\ | When an engine top end repair is needed, it's not always possible to determine if the repair can be made to only one cylinder or a complete top end teardown needs to be done. ((79-85 HD XL/XR FSM pg 3-10)) \\ | ||
| A leak-down test:\\ | A leak-down test:\\ | ||
| - | * is probably the best method to evaluate the condition of the motor top end from the outside. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=297440&page=2)) | + | * is probably the best method to evaluate the condition of the motor top end from the outside. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test/page2?t=297440&page=2)) |
| * is not designed to diagnose oil leaks but will tell you the condition of your rings, valves and head gaskets. | * is not designed to diagnose oil leaks but will tell you the condition of your rings, valves and head gaskets. | ||
| - | * will apply a known pressure to the cylinder and see how quickly it "leaks down". ((milmat1 of the XLFORUM http://xlforum.net/forums/showthread.php?p=501006)) | + | * will apply a known pressure to the cylinder and see how quickly it "leaks down". ((milmat1 of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2#post547319)) |
| * should include checking both cylinders and comparing the results, which should be similar. | * should include checking both cylinders and comparing the results, which should be similar. | ||
| + | |||
| ===== Leak-Down Test vs Compression Test ===== | ===== Leak-Down Test vs Compression Test ===== | ||
| - | + | * These are both fancy names for a deceptively simple process (installing an air gauge in the spark plug hole and noting the results). ((GOTWA of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work?t=26208)) | |
| - | * These are both fancy names for a deceptively simple process (installing an air gauge in the spark plug hole and noting the results). ((GOTWA of the XLFORUM http://xlforum.net/forums/showthread.php?t=26208)) | + | |
| * A compression test checks the cylinder's maximum pressure ability. A low reading reflects poor sealing of the chamber. | * A compression test checks the cylinder's maximum pressure ability. A low reading reflects poor sealing of the chamber. | ||
| - | * See [[techtalk:ref:trouble03|Performing a Compression Test]] in the REF section of the Sportsterpedia. | + | * See [[techtalk:ref:svcproc20|Performing a Compression Test]] in the REF section of the Sportsterpedia. |
| - | * Generally if a compression test shows anything suspect, the next step is a leak down test. ((milmat1 of the XLFORUM http://xlforum.net/forums/showthread.php?t=26208&page=2)) | + | * Generally if a compression test shows anything suspect, the next step is a leak down test. ((milmat1 of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2?t=26208&page=2)) |
| - | * A leak-down test checks the cylinder's ability to hold pressure (seal) and will reflect where the leak is occuring. | + | * A leak-down test checks the cylinder's ability to hold pressure (seal) and will reflect where the leak is occuring. \\ A leak down test is the best way to check the mechanical integrity of the motor without tearing it down. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/10013-blowby-article?t=15705)) |
| ===== When to Perform a Leak-Down Test ===== | ===== When to Perform a Leak-Down Test ===== | ||
| - | + | * A good way to keep track of the progression in engine diagnostics is to take this pressure reading when the engine is healthy. \\ Then, when you take it later as the engine life is used up, you would notice a lower pressure on the second gauge, indicating an increase in leakage. ((SHIPCHIEF of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) | |
| - | + | ||
| - | * A good way to keep track of the progression in engine diagnostics is to take this pressure reading when the engine is healthy. \\ Then, when you take it later as the engine life is used up, you would notice a lower pressure on the second gauge, indicating an increase in leakage. ((SHIPCHIEF of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | |
| * A leak-down test should be done: | * A leak-down test should be done: | ||
| * when you notice the engine performance dropping off. | * when you notice the engine performance dropping off. | ||
| Line 34: | Line 31: | ||
| ====== Engine Prep ====== | ====== Engine Prep ====== | ||
| - | |||
| **Remove the spark plugs**: This is your test point. \\ | **Remove the spark plugs**: This is your test point. \\ | ||
| * This will also allow you to turn the engine over to get the piston at TDC. | * This will also allow you to turn the engine over to get the piston at TDC. | ||
| Line 42: | Line 38: | ||
| **Piston position**: | **Piston position**: | ||
| * You can leak test a cylinder at any position so long as the valves are closed. However, TDC on Compression stroke is the accepted practice for this test. | * You can leak test a cylinder at any position so long as the valves are closed. However, TDC on Compression stroke is the accepted practice for this test. | ||
| - | * On a worn cylinder, the most wear is usually in the top inch or so, that is why there is a noticeable ridge there on a worn jug. The least wear is at the bottom inch or so. \\ So I if you want the acid test of how the rings are sealing, it should be done at or close to TDC. Put the bike in high gear to stop piston moving. ((Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311&page=2)) | + | * On a worn cylinder, the most wear is usually in the top inch or so, that is why there is a noticeable ridge there on a worn jug. The least wear is at the bottom inch or so. \\ So if you want the acid test of how the rings are sealing, it should be done at or close to TDC. Put the bike in high gear to stop piston moving. ((Hopper of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead/page2?t=48311&page=2)) |
| * The test takes only a few seconds to repeat so you can also test several locations as long as both valves are closed. | * The test takes only a few seconds to repeat so you can also test several locations as long as both valves are closed. | ||
| **Valves must be closed**: \\ | **Valves must be closed**: \\ | ||
| - | * The period of time when both valves are closed is from about halfway up on the compression stroke to about halfway down on the power stroke. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?p=501006)) \\ **TDC on the compression stroke** is about halfway between where the intake valve closes and the exhaust opens so this is a good point to set your piston. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=297440)) \\ During overlap TDC, both valves are slightly open, so you can't do your leak down test in this position with usable results. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?p=501006)) | + | * The period of time when both valves are closed is from about halfway up on the compression stroke to about halfway down on the power stroke. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2#post547319)) \\ **TDC on the compression stroke** is about halfway between where the intake valve closes and the exhaust opens so this is a good point to set your piston. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test?t=297440)) \\ During overlap TDC, both valves are slightly open, so you can't do your leak down test in this position with usable results. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2#post547319)) |
| * For the most consistent results, remove the pushrods and the valves will stay closed regardless of the piston position. \\ In this case, you can put the piston at any position you want. \\ However, this would be easier for Iron Heads since you don't have to remove the rocker boxes like the Evo's do unless you're tearing down the top end. | * For the most consistent results, remove the pushrods and the valves will stay closed regardless of the piston position. \\ In this case, you can put the piston at any position you want. \\ However, this would be easier for Iron Heads since you don't have to remove the rocker boxes like the Evo's do unless you're tearing down the top end. | ||
| - | **Remove the pushrods**: (suggested for IH engines) ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311&page=3)) \\ | + | **Remove the pushrods**: (suggested for IH engines) ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead/page3?t=48311&page=3)) \\ |
| * It is not difficult on Ironhead engines and takes only a few minutes. \\ You do not need to remove the rocker covers as you do on the Evo Sportsters with the hydraulic push rods. | * It is not difficult on Ironhead engines and takes only a few minutes. \\ You do not need to remove the rocker covers as you do on the Evo Sportsters with the hydraulic push rods. | ||
| * This is also a good idea on Evo engines also if you're already at this point in a top end teardown. | * This is also a good idea on Evo engines also if you're already at this point in a top end teardown. | ||
| * This will ensure that both valves are and will stay closed. \\ The bike will still move however as the piston is forced downward so you still may need to hold the brakes (unless you're testing with the piston at BDC). | * This will ensure that both valves are and will stay closed. \\ The bike will still move however as the piston is forced downward so you still may need to hold the brakes (unless you're testing with the piston at BDC). | ||
| - | **Remove the timing inspection plug from the crankcase**: This will be a listening area. | + | **Remove the timing inspection plug (57-03) from the crankcase**: This will be a listening area. |
| ** Remove the air cleaner**: Another listening area. \\ | ** Remove the air cleaner**: Another listening area. \\ | ||
| Line 60: | Line 56: | ||
| **The engine must be warm to get accurate results**: \\ | **The engine must be warm to get accurate results**: \\ | ||
| - | * Temperature plays a role in the results of this test. \\ It's best to do it with a warm motor ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?p=501006)) although cold tests are also valuable. | + | * Temperature plays a role in the results of this test. \\ It's best to do it with a warm motor ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2#post547319)) although cold tests are also valuable. |
| * On a warm engine, the rings, pistons, cylinders etc. have expanded closer to actual dimensions than on a cold motor. \\ Performing this test at this point will be more accurate than when everything has gotten cold and contracted. | * On a warm engine, the rings, pistons, cylinders etc. have expanded closer to actual dimensions than on a cold motor. \\ Performing this test at this point will be more accurate than when everything has gotten cold and contracted. | ||
| Line 68: | Line 64: | ||
| **Put the transmission in high gear and hold / lock the rear brakes**: | **Put the transmission in high gear and hold / lock the rear brakes**: | ||
| - | * During the leak-down test, when you apply the air pressure to the cylinder, the piston will try to be driven downward. If allowed to move, it can quickly turn the engine over, while turning the rear wheel. (How much the bike will jump depends on the gauge/pressure you're using.) | + | * During the leak-down test, when you apply the air pressure to the cylinder, the piston will try to be driven downward. \\ If allowed to move, it can quickly turn the engine over, while turning the rear wheel. (How much the bike will jump depends on the gauge/pressure you're using.) |
| - | * Therefore, secure the wheel by applying the rear brakes or it will just turn over the engine and open the exhaust valve. ((skyboltdan of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * Therefore, secure the wheel by applying the rear brakes or it will just turn over the engine and open the exhaust valve. ((skyboltdan of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| - | + | ||
| ====== Using a Differential Pressure Gauge ====== | ====== Using a Differential Pressure Gauge ====== | ||
| Line 78: | Line 72: | ||
| |{{:techtalk:ref:tools:hf_model_leak_down_tester_1_by_biknut.jpg?direct&300|}}|{{:techtalk:ref:tools:hf_leakdown_tester_14_by_hippysmack.jpg?direct&300|}}| | |{{:techtalk:ref:tools:hf_model_leak_down_tester_1_by_biknut.jpg?direct&300|}}|{{:techtalk:ref:tools:hf_leakdown_tester_14_by_hippysmack.jpg?direct&300|}}| | ||
| - | | HF Leak-Down Gauge ((photo by biknut of the XLFORUM http://xlforum.net/forums/showthread.php?t=853800)) | Cut-away showing the air path ((photo by Hippysmack)) | | + | | HF Leak-Down Gauge ((photo by biknut of the XLFORUM https://www.xlforum.net/forum/general-area/off-topic-general-discussion/99631-could-someone-please-explain-how-to-operate-a-leak-down-tester?t=853800)) | Cut-away showing the air path ((photo by Hippysmack)) | |
| - | * When using the differential pressure gauge set, ((SHIPCHIEF of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * When using the differential pressure gauge set, ((SHIPCHIEF of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| * The gauge on the left shows the regulated pressure. | * The gauge on the left shows the regulated pressure. | ||
| * Then, the air passes thru an orifice (a smaller hole inline between the two gauges to restrict the flow between them) to the second gauge. | * Then, the air passes thru an orifice (a smaller hole inline between the two gauges to restrict the flow between them) to the second gauge. | ||
| * The air then leaves the second gauge to the cylinder via the spark plug adapter. | * The air then leaves the second gauge to the cylinder via the spark plug adapter. | ||
| * This pressure (end to end) would, in a perfect engine, be the same with no cylinder, valve or head gasket leakage. No engine seals perfectly. | * This pressure (end to end) would, in a perfect engine, be the same with no cylinder, valve or head gasket leakage. No engine seals perfectly. | ||
| - | |||
| ===== Setting up the Gauge ===== | ===== Setting up the Gauge ===== | ||
| - | |||
| - | |||
| * **Before attaching the gauge to an air supply**: Turn the regulator all the way to the left (off). \\ Failure to do so can result in damage to the gauge(s). \\ | * **Before attaching the gauge to an air supply**: Turn the regulator all the way to the left (off). \\ Failure to do so can result in damage to the gauge(s). \\ | ||
| * Most gauges are subject to damage from dropping / abuse. \\ | * Most gauges are subject to damage from dropping / abuse. \\ | ||
| Line 126: | Line 117: | ||
| ====== Interpreting the Readings ====== | ====== Interpreting the Readings ====== | ||
| - | + | * The amount of air determines whether or not a repair is needed. ((Moved On / My Own Choice of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test?t=297440)) | |
| - | * The amount of air determines whether or not a repair is needed. ((Moved On / My Own Choice of the XLFORUM http://xlforum.net/forums/showthread.php?t=297440)) | + | * A fresh motor will generally show 4% - 6% with conventional rings and 1% - 2% with gapless rings. \\ 8% - 10% is not unusual for a motor with some miles on it. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work/page2#post547319)) |
| - | * A fresh motor will generally show 4% - 6% with conventional rings and 1% - 2% with gapless rings. \\ 8% - 10% is not unusual for a motor with some miles on it. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?p=501006)) | + | * In general, 10% leakage at 100 psi is well within limits especially if you have a lot of carbon build-up. ((NRHS Sales of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/28845-compression-test-results-ok/page2?t=47794&page=2)) |
| - | * In general, 10% leakage at 100 psi is well within limits especially if you have a lot of carbon build-up. ((NRHS Sales of the XLFORUM http://xlforum.net/forums/showthread.php?t=47794&page=2)) | + | * Generally less than 20% is acceptable with most engines...unless you are racing (2% percent is ideal racing spec to gain HP). Although, that much does show plenty of wear. \\ Horse power loss will start at about 25%. \\ If the two cylinders are within 5% of one another and under 20% individually, it's not really an issue. ((rick szymanski of the XLFOEUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test/page2?t=297440&page=2)) |
| - | * Generally less than 20% is acceptable with most engines...unless you are racing (2% percent is ideal racing spec to gain HP). Although, that much does show plenty of wear. \\ Horse power loss will start at about 25%. \\ If the two cylinders are within 5% of one another and under 20% individually, it's not really an issue. ((rick szymanski of the XLFOEUM http://xlforum.net/forums/showthread.php?t=297440&page=2)) | + | |
| |Motor Condition|Expected Percent Air Loss| | |Motor Condition|Expected Percent Air Loss| | ||
| Line 140: | Line 130: | ||
| - | * The actual numbers are not as important as the relationship of each cylinder. As long as both juggs are close to each other, don't sweat the actual readings. There are lots of variables that can affect those readings. ((scottfisher of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311&page=3)) | + | * The actual numbers are not as important as the relationship of each cylinder. As long as both jugs are close to each other, don't sweat the actual readings. There are lots of variables that can affect those readings. ((scottfisher of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead/page3?t=48311&page=3)) |
| - | * Make a note of the reading and the date you took it, check it again after a few rides and see if it reads the same using the same equipment. ((scottfisher of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311&page=3)) | + | * Make a note of the reading and the date you took it, check it again after a few rides and see if it reads the same using the same equipment. ((scottfisher of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead/page3?t=48311&page=3)) |
| ====== Hunting Down the Source of a Leak ====== | ====== Hunting Down the Source of a Leak ====== | ||
| - | If you've determined you have too much leakage, then it's time to deduce where the leak is going. \\ The location where the air escapes tells you what the repair is. ((Moved On / My Own Choice of the XLFORUM http://xlforum.net/forums/showthread.php?t=297440)) \\ | + | If you've determined you have too much leakage, then it's time to deduce where the leak is going. \\ The location where the air escapes tells you what the repair is. ((Moved On / My Own Choice of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test?t=297440)) \\ |
| A mechanics stethoscope [with the probe removed for this test] makes a good listening device, as does a length of oil / gas line hose. \\ | A mechanics stethoscope [with the probe removed for this test] makes a good listening device, as does a length of oil / gas line hose. \\ | ||
| There will always be some audible leakage, especially past the rings and even on a healthy engine. \\ | There will always be some audible leakage, especially past the rings and even on a healthy engine. \\ | ||
| - | Greater leakage results in a sound of lower pitch. ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) \\ | + | Greater leakage results in a sound of lower pitch. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) \\ |
| - | * **Listen at the exhaust pipe or exhaust port on the head**. ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * **Listen at the exhaust pipe or exhaust port on the head**. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| * Excessive hissing here indicates the respective exhaust valve is not sealing. | * Excessive hissing here indicates the respective exhaust valve is not sealing. | ||
| - | * **Listen at the A/C intake or intake port of the head**. ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * **Listen at the A/C intake or intake port of the head**. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| * Excessive hissing here indicates that the intake valve is not sealing. | * Excessive hissing here indicates that the intake valve is not sealing. | ||
| - | * **Listen at the timing plug hole with the plug removed**. ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * **Listen at the timing plug hole with the plug removed**. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| * Excessive hissing here indicates the rings are not sealing. | * Excessive hissing here indicates the rings are not sealing. | ||
| * Also, this could be an indication of leaking, worn or broken rings, worn piston and / or cylinder. ((79-85 HD XL/XR FSM pg 3-11)) | * Also, this could be an indication of leaking, worn or broken rings, worn piston and / or cylinder. ((79-85 HD XL/XR FSM pg 3-11)) | ||
| - | * **Listen around the cylinder to head connection**. ((IronMick of the XLFORUM http://xlforum.net/forums/showthread.php?t=48311)) | + | * **Listen around the cylinder to head connection**. ((IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/29105-cylinder-compression-and-leakage-tests-for-your-ironhead?t=48311)) |
| * Excessive hissing here indicates the respective head gasket is not sealing. | * Excessive hissing here indicates the respective head gasket is not sealing. | ||
| * **Listen around the spark plug hole(s)**. | * **Listen around the spark plug hole(s)**. | ||
| * Check to see if the O-ring seals properly on the plug adapter. | * Check to see if the O-ring seals properly on the plug adapter. | ||
| * On dual plug heads, check for leaks where the second plug mates to the head. \\ The hose can be installed in the opposite plug hole to check both areas for plug sealing. | * On dual plug heads, check for leaks where the second plug mates to the head. \\ The hose can be installed in the opposite plug hole to check both areas for plug sealing. | ||
| - | * **Listen around the crankcase vents** (those hollow bolts in the Evo heads). ((addertooth of the XLFORUM http://xlforum.net/forums/showthread.php?t=109971&page=2)) | + | * **Listen around the crankcase vents** (those hollow bolts in the Evo heads). ((addertooth of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/42399-valve-stem-seal-failure/page2?t=109971&page=2)) |
| * Excess hissing here indicates poor ring sealing. \\ | * Excess hissing here indicates poor ring sealing. \\ | ||
| Line 168: | Line 157: | ||
| These are areas that should be leak free. | These are areas that should be leak free. | ||
| - | * **For leaking valves** | + | * **Leaking Valves:** |
| - | * Try pulling the rocker cover off and tap the valve ends with the wooden handle of a hammer. \\ That will identify a sticking valve. \\ If it keeps blowing that could indicate that the edge of the valve could be burned, a bad seat or a bent valve stem. \\ Really short pipes, pinging, carbon slathered valve edges, and such will cause burned valves. ((rick szymanski of the XLFORUM http://xlforum.net/forums/showthread.php?t=297440&page=2)) | + | * Try pulling the rocker cover off and tap the valve ends with the wooden handle of a hammer. \\ That will identify a sticking valve. \\ If it keeps blowing that could indicate that the edge of the valve could be burned, a bad seat or a bent valve stem. \\ Really short pipes, pinging, carbon slathered valve edges, and such will cause burned valves. ((rick szymanski of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test/page2?t=297440&page=2)) |
| * If air is escaping through the valves: | * If air is escaping through the valves: | ||
| * Check the tappet adjustment (Pre-86 engines). ((79-85 HD XL/XR FSM pg 3-11)) | * Check the tappet adjustment (Pre-86 engines). ((79-85 HD XL/XR FSM pg 3-11)) | ||
| * Check pushrod length (86 and up engines). ((86 HD XL FSM pg 3-11)) | * Check pushrod length (86 and up engines). ((86 HD XL FSM pg 3-11)) | ||
| - | |{{:techtalk:ref:trouble:sticking_valve_3_by_73hardtail.jpg?direct&300|}}|{{:techtalk:ref:trouble:sticking_valve_4_by_73hardtail.jpg?direct&300|}}|{{:techtalk:ref:trouble:sticking_valve_5_by_73hardtail.jpg?direct&300|}}| | + | |{{techtalk:ref:svcproc:sticking_valve_3_by_73hardtail.jpg?direct&300|}}|{{techtalk:ref:svcproc:sticking_valve_4_by_73hardtail.jpg?direct&300|}}|{{techtalk:ref:svcproc:sticking_valve_5_by_73hardtail.jpg?direct&300|}}| |
| | Excess carbon between valve and seat causing a leak on this 73 XLCH. ((photo by '73hardtail of the XLFORUM)) ||| | | Excess carbon between valve and seat causing a leak on this 73 XLCH. ((photo by '73hardtail of the XLFORUM)) ||| | ||
| + | |||
| + | * **Blown Head Gasket**: | ||
| + | * A blown head gasket is usually accompanied by a chirping noise that keeps time with the pistons. ((doodah man of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/194261-lost-compression?t=2070472&highlight=compression+psi)) | ||
| ===== Dynamic Leakage (into the crankcase) ===== | ===== Dynamic Leakage (into the crankcase) ===== | ||
| Rings, by design, will allow air seepage even on a fresh motor so there will not be an instance where there is no air leakage past them. \\ | Rings, by design, will allow air seepage even on a fresh motor so there will not be an instance where there is no air leakage past them. \\ | ||
| This leads to the term "expected leakage" (or expected results). \\ | This leads to the term "expected leakage" (or expected results). \\ | ||
| - | If "substantial" (other than expected) air is going into the crank case, then there is an issue with the cylinder to piston relationship and / or integrity. ((GOTWA of the XLFORUM http://xlforum.net/forums/showthread.php?t=26208)) \\ | + | If "substantial" (other than expected) air is going into the crank case, then there is an issue with the cylinder to piston relationship and / or integrity. ((GOTWA of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/15672-four-strokes-and-leak-down-compression-tests-how-they-work?t=26208)) \\ |
| It is not uncommon to have a normally running engine show lower than expected compression during scheduled inspection or maintenance. ((https://www.aviationpros.com/article/10388599/cylinder-differential-compression-testing-subject-to-interpretation)) \\ Several factors need to be considered and some technical background is helpful in assessing the proper course of action. \\ Cylinder differential compression tests are conducted using up to 100 psi. \\ During actual engine operation, higher cylinder pressures force the rings against the cylinder. \\ The actual running dynamic seal will be different than the static measurement. \\ | It is not uncommon to have a normally running engine show lower than expected compression during scheduled inspection or maintenance. ((https://www.aviationpros.com/article/10388599/cylinder-differential-compression-testing-subject-to-interpretation)) \\ Several factors need to be considered and some technical background is helpful in assessing the proper course of action. \\ Cylinder differential compression tests are conducted using up to 100 psi. \\ During actual engine operation, higher cylinder pressures force the rings against the cylinder. \\ The actual running dynamic seal will be different than the static measurement. \\ | ||
| Line 186: | Line 178: | ||
| If the test readings are low enough to warrant a tear-down, chances are that is the next step. \\ Below are some considerations __before__ dis-assembly for clues on what to look for. \\ If the readings are on the borderline of a tear-down, these may help in some understanding for proper diagnosis. | If the test readings are low enough to warrant a tear-down, chances are that is the next step. \\ Below are some considerations __before__ dis-assembly for clues on what to look for. \\ If the readings are on the borderline of a tear-down, these may help in some understanding for proper diagnosis. | ||
| - | **If the leakage is determined to be through the rings:** | + | * **Ring Gap**: |
| - | * __Remove the test equipment, plugs back in, and crank the engine for a short amount of time and re-try the test__. ((https://www.aviationpros.com/article/10388599/cylinder-differential-compression-testing-subject-to-interpretation)) | + | * Conventional ring gaps should have been originally installed in an equidistant around each piston. \\ However, the rings will rotate as the piston moves up and down which changes the position of their respective gaps. |
| - | * **Ring Gap**: Conventional ring gaps will rotate as the piston moves up and down. | + | |
| * When the gaps on separate rings are spaced apart (vertically); | * When the gaps on separate rings are spaced apart (vertically); | ||
| * Air moves into the top gap and has to circle around the ringland to move down into the gap in the second ring and so on. | * Air moves into the top gap and has to circle around the ringland to move down into the gap in the second ring and so on. | ||
| Line 195: | Line 186: | ||
| * Air into the top ring has a faster outlet as it can move straight down through each ring without as much resistance. | * Air into the top ring has a faster outlet as it can move straight down through each ring without as much resistance. | ||
| * Running and re-testing the cylinder may rotate the gaps out of alignment and yield higher psi readings. | * Running and re-testing the cylinder may rotate the gaps out of alignment and yield higher psi readings. | ||
| - | * If either cylinder seems to be a bit over (20% or 12% respective to your year model) \\ and you are certain that the valves are closed, add a dose of oil and see if it bumps up a bit to verify a ring condition for certain. \\ Oil won't seal a sticking valve, but it will seal the ring clearance for a short duration. ((rick szymanski of the XLFOEUM http://xlforum.net/forums/showthread.php?t=297440&page=2)) | ||
| - | * Air that gets past the rings into the crankcase needs to vent somewhere. Normally it will go out the breathers. \\ If it is coming out past the pushrod tube seals, that indicates it can't make it out the breathers and it's finding a different path out. ((aswracing of the XLFORUM http://xlforum.net/forums/showthread.php?t=1530129)) | ||
| + | |{{techtalk:ref:svcproc:piston_rings_by_04xl1200c.jpg?direct&300|}}| | ||
| + | |Top 2 rings are lined up vertically on this piston ((photo by 04xl1200c of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/rubber-mount-sportster-motorcycle-talk-2004-2006/171129-04-1200c-40k-mi-engine-failure?t=1836174, edited by Hippysmack))| | ||
| + | |||
| + | * **Ringland Failure**: | ||
| + | |||
| + | |{{techtalk:ref:svcproc:ringland_failure_by_aswracing.jpg?direct&300|}}| | ||
| + | |This piston is just about to break from too much \\ cylinder pressure. This is from a race motor using \\ Nitromethane ((photo by aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/82885-piston-problems-pics?t=616889))| | ||
| + | * If either cylinder seems to be a bit over (20% or 12% respective to your year model) \\ and you are certain that the valves are closed, add a dose of oil and see if it bumps up a bit to verify a ring condition for certain. \\ Oil won't seal a sticking valve, but it will seal the ring clearance for a short duration. ((rick szymanski of the XLFOEUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/frame-mount-evo-sportster-talk-1986-2003-models/57228-leak-down-test/page2?t=297440&page=2)) | ||
| + | * Air that gets past the rings into the crankcase needs to vent somewhere. Normally it will go out the breathers. \\ If it is coming out past the pushrod tube seals, that indicates it can't make it out the breathers and it's finding a different path out. ((aswracing of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-motor-engine/sportster-motorcycle-motor-top-end/141171-air-blowby-out-pushrod-tubes-video?t=1530129)) | ||
| * **A hole in a piston would probably tell on itself** as in the pics below. \\ A dual psi gauge was set up at 92 psi, then the outlet was opened up, full hose, with the readings recorded in the second pic. \\ This left an inlet side 60 psi and outlet side of 48 psi while flowing from a small peanut air tank. It was more of a high pressure sound than a hiss. | * **A hole in a piston would probably tell on itself** as in the pics below. \\ A dual psi gauge was set up at 92 psi, then the outlet was opened up, full hose, with the readings recorded in the second pic. \\ This left an inlet side 60 psi and outlet side of 48 psi while flowing from a small peanut air tank. It was more of a high pressure sound than a hiss. | ||
| - | |{{:techtalk:ref:tools:hf_leakdown_tester_9_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:hf_leakdown_tester_10_by_hippysmack.jpg?direct&300|}}| | + | |{{:techtalk:ref:tools:hf_leakdown_tester_9_by_hippysmack.jpg?direct&300|}}|{{:techtalk:ref:tools:hf_leakdown_tester_10_by_hippysmack.jpg?direct&300|}}|{{techtalk:ref:svcproc:holed_piston_by_ironmick.jpg?direct&300|}} ((photo by IronMick of the XLFORUM https://www.xlforum.net/forum/sportster-motorcycle-forum/sportster-motorcycle-era-specific-and-model-specific/ironhead-sportster-motorcycle-talk-1957-1985/102667-my-blown-rear-piston-rings-and-cylinder-w-pics?t=896763))| |
