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techtalk:ih:engmech07 [2019/07/11 03:58]
hippysmack [77> Breather Valve (or Foo Foo Valve)]
techtalk:ih:engmech07 [2019/07/11 04:21] (current)
hippysmack [77> Breather Valve (or Foo Foo Valve)]
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 WHAT IS IT? WHAT IS IT?
   * The slang term "​FooFoo"​ comes from the annoying sound that it makes when it gets clogged up with oil residue. ((IronMick of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1332902&​page=3))   * The slang term "​FooFoo"​ comes from the annoying sound that it makes when it gets clogged up with oil residue. ((IronMick of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=1332902&​page=3))
-  * The engine breatheror crankcase vent as Harley sometimes calls it, is to allow air out of the lower crankcase, but not in, as the pistons rise and fall. ((Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=518948)) \\ Without some kind of controlled breather, the lower end would become a 1,000cc air compressor, robbing the engine of several horsepower. \\ Old time tuners like Jerry Branch, Tom Sifton and Dick O’Brien paid much attention to the engine breather ​because they knew it could give them extra horsepower if set up right.+  * The engine breather ​(or crankcase ventis to allow air out of the lower crankcase, but not in, as the pistons rise and fall. ((Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=518948)) \\ Without some kind of controlled breather, the lower end would become a 1,000cc air compressor, robbing the engine of several horsepower. \\ Old time tuners like Jerry Branch, Tom Sifton and Dick O’Brien paid much attention to the engine breather. \\ They knew it could give them extra horsepower if set up right.
   *  One thing not to do with an engine breather is to simply plumb a hose to the crankcase without some kind of one-way valve or timed breather valve. \\ It is commonly done, but it wastes power and is not good for your engine. ​   *  One thing not to do with an engine breather is to simply plumb a hose to the crankcase without some kind of one-way valve or timed breather valve. \\ It is commonly done, but it wastes power and is not good for your engine. ​
  
-WHERE IS IT? ((Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=518948))+WHERE IS IT? ((Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=518948)) ​\\
   * **Pre-1977**   * **Pre-1977**
-      * There is a timed breather valve built into the oil pump drive, which vents crankcase pressure into the cam timing chest. A six-inch metal tube hanging down from the timing cover near the generator drive, at the 6 o’clock position vents that controlled pressure to atmosphere. A metal disc on the end of the generator drive gear centrifugally separates oil from the air as it is discharged overboard.  +      * There is a timed breather valve built into the oil pump drive, which vents crankcase pressure into the cam timing chest. ​\\ A six-inch metal tube hanging down from the timing cover near the generator drive, at the 6 o’clock position vents that controlled pressure to atmosphere. ​\\ A metal disc on the end of the generator drive gear centrifugally separates oil from the air as it is discharged overboard.  
-  * **1977-78 only** ((Hopper)) ((HD Service Bulletin #M-708 dated December 1, 1976)) +  * **1977-78 only** ((Hopper)) ((HD Service Bulletin #M-708 dated December 1, 1976)) ​\\ 
-      * The timed breather on the oil pump drive was dropped. A new design breather valve (24633-77) was used in late 1977 model XL/XLCH/XLT engines produced around October 15, 1976. All 1000cc engine numbers (3A, 4A or 2G) 27940H7 and above had the new breather valve. It serves the same function as the gear driven breather valve used on 1976 and earlier engines to maintain a partial vacuum in the engine and prevent oil leakage. Due to it's improvements in doing so, it was suggested to be retrofitted to all 1977 XL & XLCH engines. +      * The timed breather on the oil pump drive was dropped. ​\\ A new design breather valve (24633-77) was used in late 1977 model XL/XLCH/XLT engines produced around October 15, 1976. \\ All 1000cc engine numbers (3A, 4A or 2G) 27940H7 and above had the new breather valve. ​\\ It serves the same function as the gear driven breather valve used on 1976 and earlier engines to maintain a partial vacuum in the engine and prevent oil leakage. ​\\ Due to it's improvements in doing so, it was suggested to be retrofitted to all 1977 XL & XLCH engines. 
-      * The one-way valve is contained in a fitting which screws into the gear-case cover below the generator mounting boss. The existing breather outlet pipe screws into the bottom of the new fitting. The outlet pipe because of its lower position must be directed outside (instead of inside) the frame tube. The rubber hose at the pipe outlet must no longer be used.+      * The one-way valve is contained in a fitting which screws into the gear-case cover below the generator mounting boss. \\ The existing breather outlet pipe screws into the bottom of the new fitting. ​\\ The outlet pipebecause of its lower positionmust be directed outside (instead of inside) the frame tube. \\ The rubber hose at the pipe outlet must no longer be used.
       * Because of the higher vacuum existing in the engines equipped with this new breather valve, a higher pressure oil pump check valve (26435-76A) was installed in L1977 oil pumps at the same time to provide higher oil pressure at the oil pressure light switch. ​       * Because of the higher vacuum existing in the engines equipped with this new breather valve, a higher pressure oil pump check valve (26435-76A) was installed in L1977 oil pumps at the same time to provide higher oil pressure at the oil pressure light switch. ​
-      * The new valve opens at 4-6 PSI whereas the old valve opens at 2-4 PSI. Pumps having the new valve are identified with a green dot. The existing 0-ring (26433- 77) was used for both new and old valves. +      * The new valve opens at 4-6 PSI whereas the old valve opens at 2-4 PSI. \\ Pumps having the new valve are identified with a green dot. \\ The existing 0-ring (26433- 77) was used for both new and old valves. 
-      *  An external non-return valve was plumbed into the vent tube sticking down from the timing cover at the generator drive. This allows air out, but not in. It is sometimes referred to as the foo-foo valve. Searching the XLFORUM for __foo foo valve__ or __foo-foo__ will lead to extensive discussions of this mystical device.+      *  An external non-return valve was plumbed into the vent tube sticking down from the timing cover at the generator drive. ​\\ This allows air out, but not in. It is sometimes referred to as the foo-foo valve. ​\\ Searching the XLFORUM for __foo foo valve__ or __foo-foo__ will lead to extensive discussions of this mystical device.
  
 |{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_1_by_hopper.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_2_by_hopper.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_3_by_hopper.jpg?​direct&​300|}}| |{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_1_by_hopper.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_2_by_hopper.jpg?​direct&​300|}}|{{:​techtalk:​ih:​oil:​77-78_ext_foo_foo_valve_3_by_hopper.jpg?​direct&​300|}}|
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   * **1979-E1982**.   * **1979-E1982**.
-      * The external foo-foo valve and the six-inch metal vent tube at the front of the timing cover were done away with. Instead, a one-way foo-foo valve was built inside the timing cover. A rubber breather hose then ran from the generator drive area of the timing cover, at the 9 o’clock position. It connected to the stock air filter so that any oil mist was fed back through the engine, making the EPA pollutocrats more happier than they were with the idea of engine oil spraying out into the atmosphereThe generator had a (1-5/​8"​ O.D.) oil separator washer on the end of the armature shaft. ((HD Service Bulletin #M-848 dated April 9, 1982))+      * The external foo-foo valve and the six-inch metal vent tube at the front of the timing cover were done away with. \\ Instead, a one-way foo-foo valve was built inside the timing cover (26909-79A),​ (26909-82)\\ A rubber breather hose then ran from the generator drive area of the timing cover, at the 9 o’clock position. ​\\ It connected to the stock air filter so that any oil mist was fed back through the engine, making the EPA pollutocrats more happier. \\ (than they were with the idea of engine oil spraying out into the atmosphere) \\ The generator had a (1-5/​8"​ O.D.) oil separator washer on the end of the armature shaft. ((HD Service Bulletin #M-848 dated April 9, 1982))
  
 Here is a pic of IronMick'​s internal foo-foo in his post-79 model on the left. \\ Here is a pic of IronMick'​s internal foo-foo in his post-79 model on the left. \\