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techtalk:ref:svcproc21 [2018/08/30 17:09] hippysmack [Dynamic Leakage (into the crankcase)] |
techtalk:ref:svcproc21 [2021/07/31 22:47] hippysmack [Engine Prep] |
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| - | ====== REF: Troubleshooting - Engine - 04 ====== | + | ====== REF: Service Procedures 21 ====== |
| ====== Cylinder Leak-Down Test ====== | ====== Cylinder Leak-Down Test ====== | ||
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| * 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)) | * 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 http://xlforum.net/forums/showthread.php?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 http://xlforum.net/forums/showthread.php?t=15705)) |
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| **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 http://xlforum.net/forums/showthread.php?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. | ||
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| * 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. \\ | ||
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| **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 http://xlforum.net/forums/showthread.php?t=48311)) | ||
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| - | * 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 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 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 http://xlforum.net/forums/showthread.php?t=48311&page=3)) | ||
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| 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 http://xlforum.net/forums/showthread.php?t=297440&page=2)) | ||
| * If air is escaping through the valves: | * If air is escaping through the valves: | ||
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| * 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 http://xlforum.net/forums/showthread.php?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. \\ | ||
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| 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. | ||
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| * 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. | ||
| + | |||
| + | |{{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 http://xlforum.net/forums/showthread.php?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 http://xlforum.net/forums/showthread.php?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 http://xlforum.net/forums/showthread.php?t=297440&page=2)) | * 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)) | * 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)) | ||
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| * **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 http://xlforum.net/forums/showthread.php?t=896763))| |
