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techtalk:evo:engmech04a [2019/02/12 16:59]
hippysmack [About Relieving Valve Pressure]
techtalk:evo:engmech04a [2019/02/17 15:39]
hippysmack [About Relieving Valve Pressure]
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 ====== Before Removing Lower Cover ====== ====== Before Removing Lower Cover ======
 ===== About Relieving Valve Pressure ===== ===== About Relieving Valve Pressure =====
 +See also [[techtalk:​ref:​svcproc16#​hydraulic_lifter_-_disassembly_inspection_assembly|Hydraulic lifter disassembly - inspection - assembly]] in the REF section of the Sportsterpedia. \\
 +
 +(also known as "​Bleeding the Lifters"​) \\
 +You are not actually doing anything but allowing the oil time to leave the lifter body out of the holes in the each lifter before removing the lower rocker mounting bolts. \\
 +Due to viscosity of the oil and hole locations, it usually takes 20-30 minutes.
 +Internal clearance and parts determine bleed rates. ((bustert of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=2039673&​highlight=bleed+lifters))
 +
 **The 86-03 FSMs state to rotate the crankshaft so both valves are closed on the head being repaired**. \\ **The 86-03 FSMs state to rotate the crankshaft so both valves are closed on the head being repaired**. \\
 Then remove the two 5/16" rocker arm retaining bolts first and remove the rocker arm shaft. \\ Then remove the two 5/16" rocker arm retaining bolts first and remove the rocker arm shaft. \\
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 This could cause the camshafts to crook sideways and gouge the bushings. \\ This could cause the camshafts to crook sideways and gouge the bushings. \\
  
-**The 04-Up FSMs changed the sequence of removing the bolts**. \\+**They 04-Up FSMs still state to rotate the crankshaft so both valves are closed on the head being repaired**. \\ 
 +**But they changed the sequence of removing the bolts**. \\ 
 Removing them in the proper order also prevents potentially warpage of the cover(s). ((Screw Loose Dan of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1488750)) \\ Removing them in the proper order also prevents potentially warpage of the cover(s). ((Screw Loose Dan of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1488750)) \\
 It also mentions making sure that both valves are closed prior to removal for each cylinder (separately) of the rocker box you're removing. \\ It also mentions making sure that both valves are closed prior to removal for each cylinder (separately) of the rocker box you're removing. \\
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 |Photos of a dry lifter. (L) assembled - (R) with spring pressure at rest. On dry assembly, the pushrod cup is \\ relatively easy to push in with you finger to install the retainer clip. If oil was poured into the lifter body and \\ then the cup was compressed, it would be more difficult to push the cup down to install the retainer. ((photos by Hippysmack)) ​ || |Photos of a dry lifter. (L) assembled - (R) with spring pressure at rest. On dry assembly, the pushrod cup is \\ relatively easy to push in with you finger to install the retainer clip. If oil was poured into the lifter body and \\ then the cup was compressed, it would be more difficult to push the cup down to install the retainer. ((photos by Hippysmack)) ​ ||
 |{{:​techtalk:​ref:​svcproc:​lifter_disassembly_2_by_hippysmack.jpg?​direct&​300|}}|{{:​techtalk:​ref:​svcproc:​lifter_disassembly_6_by_hippysmack.jpg?​direct&​300|}}| |{{:​techtalk:​ref:​svcproc:​lifter_disassembly_2_by_hippysmack.jpg?​direct&​300|}}|{{:​techtalk:​ref:​svcproc:​lifter_disassembly_6_by_hippysmack.jpg?​direct&​300|}}|
 +
 +
 +**Cam lobe positions**:​
 +Rocker boxes should really only be removed and installed when the cams are positioned such that the lifters are let all the way down. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​p=5041422&​highlight=rocker+box#​post5041422)) \\
 +Compression TDC is the best place to do this, because it's just about exactly halfway through the valve-closed window. \\
 +If you install the rocker boxes at overlap TDC instead, both valves are slightly open. So it's important to be able to tell compression TDC from overlap TDC. \\
 +
 +Ten minutes or so is a pretty normal amount of time for lifter bleed down. \\
 +It may take longer if it's particularly cold or if you're using heavy oil. \\
 +But if you're sitting at overlap TDC, you may never see the valves close because the lifter will shorten as far as it goes and still be too long. \\
  
 **There are two TDC's for EACH cylinder**. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1874585)) \\ **There are two TDC's for EACH cylinder**. ((aswracing of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1874585)) \\