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techtalk:ih:carb01r [2020/04/01 20:17]
hippysmack [IH: Carburetor, Intake Manifold & Exhaust Systems - Sub-01R]
techtalk:ih:carb01r [2020/08/03 23:45] (current)
hippysmack [Keihin Butterfly Carb (non CV) Functions, Adjustments, Tuning]
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   * [[techtalk:​ih:​carb01q|Rebuilding the Keihin Butterfly Carb]]   * [[techtalk:​ih:​carb01q|Rebuilding the Keihin Butterfly Carb]]
   * [[techtalk:​ih:​carb01p|Keihin Butterfly Carb Identificaton]]   * [[techtalk:​ih:​carb01p|Keihin Butterfly Carb Identificaton]]
 +  * [[techtalk:​miscres:​miscres05#​tsb_650-699|See TSB #694 for introduction information on the Keihin butterfly carb]]. \\ Click the link to view the TSB page in the Sportsterpedia. Then click on the "​Y"​ next to #694 to view / download the PDF. \\
 +\\
  
 For Late 1976-1987 Sportsters. \\ For Late 1976-1987 Sportsters. \\
 If you are opening up your carb for the first time, you need three things: \\ If you are opening up your carb for the first time, you need three things: \\
-  - A FSM (Factory Service Manual) for you year model.+  - A FSM (Factory Service Manual) for your year model.
   - A factory Parts Catalog. ​   - A factory Parts Catalog. ​
   - A good rebuild kit (new rubbers all through a carb make a big difference to it's performance)   - A good rebuild kit (new rubbers all through a carb make a big difference to it's performance)
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 With the plug installed, the pilot jet draws fuel from and through the main jet. \\ With the plug installed, the pilot jet draws fuel from and through the main jet. \\
 You must run with the plug in place or the main jet will be bypassed by the drilled passage and it will run very rich. \\ You must run with the plug in place or the main jet will be bypassed by the drilled passage and it will run very rich. \\
 +
 +**Correction of Lean Mixture Problems Due to the Rubber Bung** \\
 Sometimes, the black plug in the low speed jet is too long and should be trimmed off to allow more fuel in the low speed side. ((oldnavy of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=877868&​page=2)) \\  Sometimes, the black plug in the low speed jet is too long and should be trimmed off to allow more fuel in the low speed side. ((oldnavy of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=877868&​page=2)) \\ 
-Trim off as much as needed to still hold it in without falling out about 1/8"This was factory fix. \\+Trim off as much as needed to still hold it in without falling out. Per TSB #707, correct by either modifying or replacing the plug. ((HD TSB #M707 dated December ​1, 1976)) \\ 
 +Either cut a plug so it is 5mm (.20") from shoulder to tip or replace it with new plug (27385-76). Refer to bulletin 694 for disassembly and assembly procedure to remove and replace plug. \\
 Screaming Eagle Keihin carbs do not use the rubber bung. \\  Screaming Eagle Keihin carbs do not use the rubber bung. \\ 
  
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 But if you were desperate you could poke a bristle from a wire brush in there, very carefully. \\ But if you were desperate you could poke a bristle from a wire brush in there, very carefully. \\
 And don't lose the bristle down the manifold, it will wreck your engine, being hardened spring steel. \\ And don't lose the bristle down the manifold, it will wreck your engine, being hardened spring steel. \\
 +
 +**Correction of Air Leakage at Carburetor Body Plugs** \\
 +As a precautionary measure to eliminate possible air leakage, apply an adhesive type sealer, such as Harley-Davidson Seal-All, to the two welch plugs in top of carb. ((HD TSB #M-707 dated December 1, 1976)) \\
 +Apply a minimal amount only to the joints between the edges of the plugs and the casting. \\
  
 |Idle transfer ports inside. ((photo by Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=276157&​page=3))|Idle transfer ports outside. ((photo by Civil War Harley of the XLFORUM, annotated by Hippysmack ​ http://​xlforum.net/​forums/​showthread.php?​t=2002662&​highlight=keihin+accelerator+pump&​page=2))| |Idle transfer ports inside. ((photo by Hopper of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=276157&​page=3))|Idle transfer ports outside. ((photo by Civil War Harley of the XLFORUM, annotated by Hippysmack ​ http://​xlforum.net/​forums/​showthread.php?​t=2002662&​highlight=keihin+accelerator+pump&​page=2))|
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 The accelerator pump is operated by a rod attached to a spring loaded bell crank mounted on the throttle butterfly shaft. \\ The accelerator pump is operated by a rod attached to a spring loaded bell crank mounted on the throttle butterfly shaft. \\
 When you open the throttle, the spring is wound up and forces the rod down. How far the rod travels determines how much gas is forced into the carb's throat. \\ When you open the throttle, the spring is wound up and forces the rod down. How far the rod travels determines how much gas is forced into the carb's throat. \\
 +
 +**Correction of Faulty Accelerator Pump Operation** \\
 +With engine warm and running at idle, remove air cleaner cover and see if any fuel is leaking from accelerator pump nozzle due to the accelerator pump rod being too long. ((HD TSB #M707 dated December 1, 1976)) \\
 +Correct by removing the rod as detailed in bulletin 694 and shortening to 59.50mm. (2.34"​). \\
 +Caution: Do not over-shorten because this will affect pump action and cause poor acceleration. \\
  
 ====== Tuning the Accel pump ====== ====== Tuning the Accel pump ======
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 ====== Heat Spacer ====== ====== Heat Spacer ======
-**The insulating block was never suggested for use on Sportster Keihin butterfly carbs by the MoCo**. \\ 
-In December of 1976, insulating block (27412-57) was suggested to use on 76 and later FL and FX models (one block on FX and two blocks on FL models). ((HD TSB #M707 dated December 1, 1976)) \\ 
-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. \\ 
  
 +[[techtalk:​ih:​carb01#​heat_spacer_insulator_block|Click here to see Heat Spacer / Insulator Block]] on the main IH carb page. \\
 ====== Vacuum Ports (83-up) ====== ====== Vacuum Ports (83-up) ======
 **VOES port**. \\ **VOES port**. \\
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     * If the problem is crud, then it can often be fixed at least temporarily by partially emptying the float bowl. ((Ironmick of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=507935&​page=2)) \\ While running, shut off the fuel valve, run the bike until it begins to sputter, then turning on the fuel. \\ The sudden rush of fuel may dislodge the crud and you are good to go for a while. This can be done either while riding or while just idling. \\ This should wash out debris in the float valve / seat.     * If the problem is crud, then it can often be fixed at least temporarily by partially emptying the float bowl. ((Ironmick of the XLFORUM http://​xlforum.net/​forums/​showthread.php?​t=507935&​page=2)) \\ While running, shut off the fuel valve, run the bike until it begins to sputter, then turning on the fuel. \\ The sudden rush of fuel may dislodge the crud and you are good to go for a while. This can be done either while riding or while just idling. \\ This should wash out debris in the float valve / seat.
   * **Damage or debris around valve seat**.   * **Damage or debris around valve seat**.
-  * **Too high float level**. +  * **Too high float level**. ​\\ See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.
-    * See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.+
   * **Worn float mounting tabs, float pin or loose float retaining screw**.   * **Worn float mounting tabs, float pin or loose float retaining screw**.
   * **Cracked or damaged overflow tube in the float bowl**.   * **Cracked or damaged overflow tube in the float bowl**.
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 **Check for**: \\ **Check for**: \\
-  * **Improper idle mixture adjustment**:​ See [[techtalk:​ih:​carb01r#​overall_adjusting_procedure|Overall Adjusting Procedure]] above.+  ​* **Float setting too low**. See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above. 
 +  ​* **Improper idle mixture adjustment**: ​\\ See [[techtalk:​ih:​carb01r#​overall_adjusting_procedure|Overall Adjusting Procedure]] above.
   * **Damaged mixture screw**.   * **Damaged mixture screw**.
   * **Clogged bypass or idle ports**.   * **Clogged bypass or idle ports**.
   * **Clogged slow jet**.   * **Clogged slow jet**.
   * **Loose slow jet**.   * **Loose slow jet**.
-  * **Air leaks**.+  * **Air leaks**. See [[techtalk:​ih:​carb01r#​running_lean|"​Testing for air leaks"​]] below.
   * **Excess or sloppy fuel from accelerator pump**.   * **Excess or sloppy fuel from accelerator pump**.
   * **Improper fast idle adjustment on 79-up carbs**:   * **Improper fast idle adjustment on 79-up carbs**:
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     * A fast idle can also be caused by an advance mechanism that is not functioning correctly. \\     * A fast idle can also be caused by an advance mechanism that is not functioning correctly. \\
   * **Mechanical issues with choke or throttle shaft / parts**.   * **Mechanical issues with choke or throttle shaft / parts**.
 +  * **Erratic Idle Due to Fuel Vaporization** (especially in stop and go or at stoplights)
 +    * Insure the fuel hose isn't touching a head / cylinder to add extra heat to the fuel.
 +    * Consider installing a heat spacer between the carb and manifold. \\ See [[techtalk:​ih:​carb01#​heat_spacer_insulator_block|Heat Spacer / Insulator Block]]
  
  
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   * **Clogged bypass (idle transfer) ports**.   * **Clogged bypass (idle transfer) ports**.
   * **Clogged or too small of a slow jet / bleed tube**.   * **Clogged or too small of a slow jet / bleed tube**.
-  * **Float setting too low**. +  * **Float setting too low**. See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.
-    * See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.+
  
 ===== Hard Starting ===== ===== Hard Starting =====
 **Check for**: \\ **Check for**: \\
-  * **Improper idle mixture adjustment**:​ See [[techtalk:​ih:​carb01r#​overall_adjusting_procedure|Overall Adjusting Procedure]] above.+  * **Improper idle mixture adjustment**: ​\\ See [[techtalk:​ih:​carb01r#​overall_adjusting_procedure|Overall Adjusting Procedure]] above.
   * **Choke not adjusted properly / not operating properly**.   * **Choke not adjusted properly / not operating properly**.
   * **Clogged jets or internal passages in the carb.**.   * **Clogged jets or internal passages in the carb.**.
-  * **Wrong float setting**. +  * **Wrong float setting**. ​\\ See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.
-    * See [[techtalk:​ih:​carb01r#​float_level_adjustment|Float level adjustment]] above.+
   * **Fuel valve on tank not turned on**.   * **Fuel valve on tank not turned on**.
   * **Loose bowl screws**.   * **Loose bowl screws**.
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     * Running hot can be caused by vacuum leaks or bad ignition events.     * Running hot can be caused by vacuum leaks or bad ignition events.
   * **Causes**:   * **Causes**:
 +    * On 1977-up carbs, the rubber plug over the slow jet may be too long causing a lean mixture.
 +      * See [[techtalk:​ih:​carb01r#​rubber_bung|Correction of Lean Mixture Problems Due to the Rubber Bung]] above.
     * Jets too small.     * Jets too small.
     * Float level too low.     * Float level too low.