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| techtalk:ref:svcproc20 [2020/03/02 05:41] – [Compression Calculator] hippysmack | techtalk:ref:svcproc20 [2024/01/22 05:24] (current) – hippysmack | ||
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| ====== REF: Service Procedures 20 ====== | ====== REF: Service Procedures 20 ====== | ||
| ====== Cylinder Compression Test ====== | ====== Cylinder Compression Test ====== | ||
| - | A compression test should be done as part of each tune-up. Record the results and follow any changes over time. ((IronMick of the XLFORUM | + | A compression test should be done as part of each tune-up. Record the results and follow any changes over time. ((IronMick of the XLFORUM |
| * The compression tester has a one-way valve in it's hose, allowing it to see the pressure of the compression stroke\\ but not relieve it on the other strokes. Additional strokes that produce higher pressures will increase the\\ reading of the gauge. | * The compression tester has a one-way valve in it's hose, allowing it to see the pressure of the compression stroke\\ but not relieve it on the other strokes. Additional strokes that produce higher pressures will increase the\\ reading of the gauge. | ||
| - | * Always look for a compression tester that has it's check valve as near to the chamber as possible. Otherwise, you' | + | * Always look for a compression tester that has it's check valve as near to the chamber as possible. Otherwise, you' |
| * A proper compression test should be done with the engine close to normal operating temperature, | * A proper compression test should be done with the engine close to normal operating temperature, | ||
| - | |||
| ===== Compression Test vs Leak-Down Test ===== | ===== Compression Test vs Leak-Down Test ===== | ||
| - | + | | |
| - | | + | |
| * A compression test checks the cylinder' | * A compression test checks the cylinder' | ||
| - | * Generally if a compression test shows anything suspect, the next step is a leak down test. ((milmat1 of the XLFORUM | + | * Generally if a compression test shows anything suspect, the next step is a leak down test. ((milmat1 of the XLFORUM |
| * A leak-down test checks the cylinder' | * A leak-down test checks the cylinder' | ||
| * See also [[techtalk: | * See also [[techtalk: | ||
| - | |||
| ====== Test Each Cylinder for Compression ====== | ====== Test Each Cylinder for Compression ====== | ||
| - | - Ride the bike to get the engine up to operating temperature. ((IronMick of the XLFORUM | + | - Ride the bike to get the engine up to operating temperature. ((IronMick of the XLFORUM |
| - Disconnect the power to the coil to prevent it from firing. | - Disconnect the power to the coil to prevent it from firing. | ||
| - | * The extra two plugs (on dual plug heads) need to remain in place during this test. ((IXL2Relax of the XLFORUM | + | * The extra two plugs (on dual plug heads) need to remain in place during this test. ((IXL2Relax of the XLFORUM |
| * If you can't disconnect power to the coil, ground out all the plug wires. | * If you can't disconnect power to the coil, ground out all the plug wires. | ||
| - Clean the area around the spark plugs __BEFORE__ you remove them. ((79-85 HD XL/XR FSM pg 3-10)) | - Clean the area around the spark plugs __BEFORE__ you remove them. ((79-85 HD XL/XR FSM pg 3-10)) | ||
| - | * If you haven' | + | * If you haven' |
| - Connect the compression gauge to the first cylinder. | - Connect the compression gauge to the first cylinder. | ||
| - Make sure the **throttle plate is fully open** (and the choke, if present) before turning over the engine. | - Make sure the **throttle plate is fully open** (and the choke, if present) before turning over the engine. | ||
| - | * If using a CV carb, **hold the slide up.** ((aswracing | + | * If using a CV carb, **hold the slide up.** ((aswracing |
| * If the cylinder can't freely pull in air, the compression reading will be low. | * If the cylinder can't freely pull in air, the compression reading will be low. | ||
| * **Do NOT pull the enrichener knob** - The enrichener is mis-named a choke (' | * **Do NOT pull the enrichener knob** - The enrichener is mis-named a choke (' | ||
| - | - Crank the engine continuously through 5-7 compression strokes. (until there is no further increase in reading at the gauge) ((IronMick of the XLFORUM | + | - Crank the engine continuously through 5-7 compression strokes. (until there is no further increase in reading at the gauge) ((IronMick of the XLFORUM |
| - Record the readings at the end of the first and last strokes for this cylinder. | - Record the readings at the end of the first and last strokes for this cylinder. | ||
| - If you get a lower than normal reading, add app. 1/2 ounce of oil into the cylinder, repeat the compression test to see if the reading will increase. Record the oil-added readings. | - If you get a lower than normal reading, add app. 1/2 ounce of oil into the cylinder, repeat the compression test to see if the reading will increase. Record the oil-added readings. | ||
| - Repeat for the second cylinder. | - Repeat for the second cylinder. | ||
| - | {{techtalk: | + | {{techtalk: |
| ====== Interpreting the Readings ====== | ====== Interpreting the Readings ====== | ||
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| | Notes: The recorded results between the two cylinders should be within 10psi of each other.\\ PSI expectations are from HD manuals. | | Notes: The recorded results between the two cylinders should be within 10psi of each other.\\ PSI expectations are from HD manuals. | ||
| - | + | | |
| - | | + | |
| * Pumping up too fast means the exhaust isn't opening (pushrod worn too much or loose enough to fall out of place). | * Pumping up too fast means the exhaust isn't opening (pushrod worn too much or loose enough to fall out of place). | ||
| * Pumping up too slow is the usual suspect list below: | * Pumping up too slow is the usual suspect list below: | ||
| Line 88: | Line 84: | ||
| **Possible Cause**: \\ | **Possible Cause**: \\ | ||
| Piston ring gap too tight upon installation. ((Jörgen)) \\ | Piston ring gap too tight upon installation. ((Jörgen)) \\ | ||
| - | **Full Article**: | + | **Full Article**: |
| - | **Pics of the Damage**: ((Photos by sep69 of the XLFORUM | + | **Pics of the Damage**: ((Photos by sep69 of the XLFORUM |
| |{{techtalk: | |{{techtalk: | ||
| ====== Compression Calculator ====== | ====== Compression Calculator ====== | ||
| - | Article by aswracing of the XLFORUM ((http:// | + | Article by aswracing of the XLFORUM ((https://www.xlforum.net/ |
| + | |||
| + | [[http:// | ||
| So how much compression can you run with what cams, and still be able to run pump gas? \\ | So how much compression can you run with what cams, and still be able to run pump gas? \\ | ||
| Line 115: | Line 113: | ||
| To solve the problem, you need to dust off your trigonometry textbook and make right triangles out of it. \\ | To solve the problem, you need to dust off your trigonometry textbook and make right triangles out of it. \\ | ||
| - | Or, you could take the easy way and [[http:// | + | Or, you could take the easy way and just download the calculator. \\ |
| Store the file somewhere on your hard drive where it's easy to find, and then double click on it to execute. \\ | Store the file somewhere on your hard drive where it's easy to find, and then double click on it to execute. \\ | ||
| - | |||
| The program is very easy to use, and it will give progressively more info as you enter more data: \\ | The program is very easy to use, and it will give progressively more info as you enter more data: \\ | ||
| * For just displacement, | * For just displacement, | ||
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| With good chamber turbulence and dual plugs, you can even run it higher, up to 9.5:1 is not unusual. \\ | With good chamber turbulence and dual plugs, you can even run it higher, up to 9.5:1 is not unusual. \\ | ||
| - | This is a free tool, independently developed in-house by aswracing of the XLForum | + | This is a free tool, independently developed in-house by Hammer Performance ((aswracing of the XLForum)). \\ |
| Feel free to use it and distribute it as you please. \\ | Feel free to use it and distribute it as you please. \\ | ||
| It's virus-free. \\ | It's virus-free. \\ | ||
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| All it does is perform the calculations and give you the answer. \\ | All it does is perform the calculations and give you the answer. \\ | ||
| + | Note that results given by this program are intended as a guideline only. \\ | ||
| + | HAMMER PERFORMANCE assumes no responsibility for what you do with the information presented. \\ | ||
| - | {{: | + | {{: |
