Differences

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--- techtalk:ih:carb01r [2019/10/15 00:33]
hippysmack [76-78 38mm Keihin's]
+++ techtalk:ih:carb01r [2020/08/03 20:59]
hippysmack [Heat Spacer]
@@ Line 24: / Line 24: @@
 {{:techtalk:ih:carb:keihin_buttefly_ac_side_functions_by_spuggy_-_annotated_by_hippysmack.jpg?direct&300|}} ((photo by spuggy of the XLFORUM, annotated by Hippysmack http://xlforum.net/forums/showthread.php?p=5694195&highlight=keihin#post5694195))
-====== Service Bulletin Information ======
@@ Line 115: / Line 113: @@
 The idle mixture screw is held in place by a spring on top of the carburetor near the intake mounting flange on all models. \\
-  * On 76-78 carbs, the screw and it's spring is sticking up in plain site.
+  * On 76-78 carbs, the screw and it's spring is sticking up in plain site. \\ 76 carbs didn't come with a seal on the mixture screw. It was added thru a service bulletin in December of 1976. ((HD TSB #M707 dated December 1, 1976)) \\ The ID of the seal (27355-76) was a little small and it was suggested to enlarge the hole slightly for the screw. \\ It was to be placed between the spring and the carb body. This still leaves the spring being able to cut the seal.
-  * On 79 carbs, the screw is inside a towered boss under a limiter cap. \\ The limiter cap can be removed to adjust the mixture screw. However, with the cap on, the mix can still be adjusted with the limits of the cap.
+  * On 79 carbs, the screw is inside a towered boss under a limiter cap. \\ The limiter cap can be removed to adjust the mixture screw. However, with the cap on, the mix can still be adjusted with the limits of the cap. \\ A washer between the seal (O-ring) and the spring was added in 79 to protect the rubber O-ring from damage from the spring.
   * On 80-up carbs, the screw is inside a towered boss under a (non removable) plug. \\ The plug can be removed by drilling a small hole through it and using a small screwdriver to pop it out. \\ Wrap a piece of tape around the drill bit as a guide so you won't drill into the mixture screw.
@@ Line 154: / Line 152: @@
 |{{:techtalk:ih:carb:keihin_butterfly_carb_2_by_hopper.jpg?direct&300|}}|
+==== Choke Shaft and Plastic Parts (76-E78) ====
+Kits were available from the MoCo for 76-78 FX & FL carbs to adapt for a fast idle cam. It was also available as a replacement for 79-up carbs. \\
+The Choke Shaft Kit is (27045-78) and the Plastic Parts kit (27046-78) as shown below (with the parts list including 3 springs, 2 clips and 2 washers). \\
+{{:techtalk:ih:carb:keihin_choke_shaft_kit_27045-78.jpg?direct&300|}} {{:techtalk:ih:carb:keihin_plastic_parts_kit_27046-78.jpg?direct&300|}} \\
+The ball under the choke lever drive must ride in the detents on the bottom of the choke lever drive. \\
 ==== Fast Idle Cam (79-up) ====
@@ Line 427: / Line 431: @@
 Any wiring that that may get too hot / catch fire doesn't need gas nearby. \\
-While installing the accelerator pump, the diaphragm goes on first, then spring, then cover. \\
+|After adjusting. ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3))|Accelerator pump from the outside. \\ (see caution above) ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3))|
-Make sure those two square section O-rings are in place and in good condition. Else, gas will leak out there instead of getting squirted into your engine. \\
+|{{:techtalk:ih:carb:keihin_butterfly_carb_15_by_hopper.jpg?direct&300|}}|{{:techtalk:ih:carb:keihin_butterfly_carb_16_by_hopper.jpg?direct&300|}}|
-|After adjusting. ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3))|Accelerator pump from the outside. \\ (see caution above) ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3))|Check position of O-rings. ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3))|
-|{{:techtalk:ih:carb:keihin_butterfly_carb_15_by_hopper.jpg?direct&300|}}|{{:techtalk:ih:carb:keihin_butterfly_carb_16_by_hopper.jpg?direct&300|}}|{{:techtalk:ih:carb:keihin_butterfly_carb_17_by_hopper.jpg?direct&300|}}|
 ===== Andrews High Flow Accelerator Pump (Keihin butterfly) =====
@@ Line 538: / Line 539: @@
 ====== Heat Spacer ======
-**The insulating block was never suggested for use on Sportster Keihin butterfly carbs by the MoCo**. \\
-In August of 1977, a Service Bulletin was issued regarding the use of a spacer block on 1977→ 1200CC engines. ((HD TSB #M715 dated August 12, 1977)) \\
-In that, it is suggested to install a 'new available' spacer block (5895) on 1200CC engines between the intake manifold and the carburetor. \\
-It's purpose was to prevent erratic idle or spit-back through the carb in slow moving traffic or at high ambient temperature. \\
-Some Sportster owners say they have never needed them and others use them regularly. \\
-**Argument for using the spacer**: \\
-((photo by Robicycle of the XLFORUM http://xlforum.net/forums/showthread.php?t=1663198&highlight=keihin+bowl)) ((photo by Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3)) {{ :techtalk:ih:carb:keihin_butterfly_carb_6_by_hopper.jpg?direct&300|}} \\ {{ :techtalk:ih:carb:keihin_butterfly_carb_4_by_robicycle.jpg?direct&300|}} \\
-The Phenolic fiber spacer helps with hot idle or starting problems. One infuriatingly simple thing that affects idle, starting and carb farts when your engine is hot, is this phenolic fiber spacer. ((Hopper of the XLFORUM http://xlforum.net/forums/showthread.php?t=276157&page=3)) It's between the carb and manifold, which some models had and others did not. It stops engine heat from flowing into the carb. If your model doesn't have one of these stock, you can cut one out of a sheet of fiber about 3/16" thick. JP Cycles or others sell one that is a bit thicker and might work even better. There should be a gasket on each side of the spacer while still using the rubber O-ring on the carb flange. Of course, make sure both the carb flange and the manifold are filed nice and flat with a 10-inch flat file first. Without it, your carb can get too hot to touch within minutes of the bike being parked with a hot engine. Even the air filter gets hot. There is a lot of heat flowing from the heads, up the manifold and into the carb which makes it hard to start and idle rough. The heat vaporizes the fuel in the float bowl and it can boil and come out the overflow tube at the bottom of the float bowl. This also means the tiny amount of fuel trying to go through the idle adjuster screw and into the carb throat can also vaporize. Fuel going into the engine needs to be tiny globules of liquid fuel, not vapor. Putting a heat-blocking spacer on is really worth the effort if you ride a lot in city traffic. (where idling at the lights will allow heat to flow into the carb while there is no cooling wind) With a kick only XLCH, the easier hot starting is a Godsend. \\
-Gas getting to the boiling can happen for several reasons. \\
-Having the gas line resting against the engine, the float set too low and others will also attribute to boiling gas. \\
 ====== Vacuum Ports (83-up) ======
@@ Line 582: / Line 571: @@
 Most carburetor problems really are electrical, just like the old timers always say. (Hopper)
+===== Altitude and Ambient Temps =====
+A Carb works by mixing air and fuel into a vaporous mixture. We want the ideal mixture so the bike runs well. ((stevo of the XLFORUM http://xlforum.net/forums/showthread.php?t=49078)) \\
+Unfortunately it's not quite simple as a carburetor mixes air by a set volume to set the amount of fuel. \\
+The amount of oxygen density in that set amount of air varies and this is what gives variations in mixture due to differing conditions. \\
+The required air / fuel mixture changes depending on the conditions. \\
+Max power for acceleration is around 12.5 parts air to one part fuel. \\
+Chemically correct or stoichiometric is 14.7:1 \\
+A rich mixture misfire usually needs about 6-7:1 \\
+A lean mixture misfire usually needs over 20:1 \\
+We want to try and get the most fuel in there that we can but the limiting factor is the amount of oxygen that we can fit in there and give the correct ratio. \\
+A number of things have an effect on the amount of oxygen we can get in there. \\
+Just like you run out of breath at altitude because of lack of oxygen, so does your bike. \\
+  * Carburetor modification kits (including jet(s) and an accelerator pump stop screw) were made available for 1200cc, 1340cc and 1000cc models to provide leaner fuel mixtures when operating at elevations above 4000 feet sea level. ((HD Service Blletin #M-730 dated June 15, 1978))
+    * Normally, leaner fuel/air mixtures are required for proper engine operation as the elevation above sea level increases. The decreased jet sizes and accelerator pump modifications should be installed where there is evidence of a rich condition causing loss of smooth combustion, stumbling on acceleration or such other carburetor issues at high altitudes.
+    * High Altitude Kits:
+      * 1978 1/2 FLH-1200 (27094-78). \\ Consisted of a 160 main jet, 72 slow jet and a label for the downtube. \\ In addition to installing the parts on the carb, the FLH-1200 models required changing the position of the accelerator pump spring pre-load position. \\ The spring should go in the top (#1) position as opposed to the #3 (std) position on the pump lever.
+      * FX/FXE/FXS-1200 (27095-78). \\ Consisted of an accelerator pump screw and a label for the downtube. \\ Install and adjust the accel pump stop screw to extend 1/8" past hole in lever.
+      * XLH/XLCH/XLCR-1000 (27096-79). \\ Consisted of a 160 main jet, an accelerator pump screw and a label for the downtube. \\ Install and adjust the accel pump stop screw to extend 1/8" past hole in lever.
+      * FLH-80, 1340cc, (27093-78). \\ Consisted of a 155 main jet and a label for the downtube.
+**Note**, any motorcycle modified for high altitude operation must be converted back to standard if operated at altitudes below 4000 feet. \\ An overly lean condition can cause engine damage.
+The air pressure or barometric pressure is higher at sea level than at high altitude. \\
+The more pressure we have means the more oxygen in the same amount of air. \\
+Example: \\
+The bike is jetted for the correct mixture at sea level. Then you go up the mountains. \\
+The higher the altitude, the less oxygen, and the richer the bike will run. \\
+The opposite is also true. \\
+Hotter Air = Less Oxygen → Richer Mix ((stevo of the XLFORUM http://xlforum.net/forums/showthread.php?t=49078)) \\
+Colder Air = More Oxygen → Leaner Mix \\
+Higher Barometric Pressure (Low Altitude) = More Oxygen → Leaner Mix \\
+Lower Barometric Pressure (Higher Altitude) = Less Oxygen → Richer Mix \\
+Higher Humidity = Less Oxygen → Richer Mix \\
+Lower Humidity = More Oxygen → Leaner Mix \\
 ===== Fuel overflow =====
 The overflow tube is a safety feature in case the float needle does not prevent flow and the bowl gets full. ((IXL2Relax of the XLFORUM http://xlforum.net/forums/showthread.php?t=2071025)) \\
@@ Line 752: / Line 777: @@
 ====== Helpful Links ======
 **Video**: \\
-Here are some excellent videos of servicing the pre-CV Keihin Butterfly carbs:((Used by permission - SportsterPavel at the XLForum - http://xlforum.net/forums/showthread.php?t=2055701))
+Here are some excellent videos of servicing the pre-CV Keihin Butterfly carbs: ((Used by permission - SportsterPaul at the XLForum - http://xlforum.net/forums/showthread.php?t=2055701))
   * [[https://youtu.be/f_Ek37GEEN4|#1 - Tips and tricks.]]\\

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