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techtalk:ih:carb01 [2020/08/03 20:47] hippysmack [Swapping to a Keihin CV Carb] |
techtalk:ih:carb01 [2020/08/03 21:39] hippysmack [Carb to Manifold Insulator Blocks] |
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| * The original idle mixture setting for E76 Keihin carbs was 1-1/2 turns out and adjust from there. ((TSB #694 dated November 7, 1975)) \\ In December of 1976, that was changed to 7-8 turns out for FL and FX models. ((HD TSB #M-707 dated December 1, 1976)) \\ In June of 1977, L77-up FL and FX models were changed back to 1-1/2 turns out with earlier models remaining at 7/8 turns. | * The original idle mixture setting for E76 Keihin carbs was 1-1/2 turns out and adjust from there. ((TSB #694 dated November 7, 1975)) \\ In December of 1976, that was changed to 7-8 turns out for FL and FX models. ((HD TSB #M-707 dated December 1, 1976)) \\ In June of 1977, L77-up FL and FX models were changed back to 1-1/2 turns out with earlier models remaining at 7/8 turns. | ||
| - | ====== Carb to Manifold Insulator Blocks ====== | + | ====== Heat Spacer / Insulator Block ====== |
| + | **The insulating block was never suggested for use on Sportster Bendix or 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)) \\ | ||
| + | This was suggested to eliminate erratic idle due to fuel vaporization in slow moving traffic or at high ambient temperatures. \\ | ||
| + | The engine temperature may rise to the point where it heats the carburetor enough to boil the fuel. \\ | ||
| + | When this happens, the engine can idle erratically and stop. To prevent this, place the insulating block(s) between the engine and carburetor. \\ | ||
| + | [[techtalk:miscres:miscres05#tsb_700-749|Click here to view the TSB page in the Sportsterpedia]]. Click on the "Y" next to M-707 to view download the PDF. \\ | ||
| + | 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)) \\ | ||
| + | The bulletin addresses proper installation for better sealing of the carb to A/C and carb/insulator block/manifold seal. \\ | ||
| + | [[techtalk:miscres:miscres05#tsb_700-749|Click here to view the TSB page in the Sportsterpedia]]. Click on the "Y" next to M-715 to view download the PDF. \\ | ||
| + | This kit was also suggested for installation of the spacer block. \\ | ||
| + | |PART #|DESCRIPTION|QUANTITY|REPLACES| | ||
| + | |7739|LOCK NUT \\ 5/16"-18 x 11/32" X 1/2" Hex| 2 | 7725 | | ||
| + | |5895|INSULATING SPACER| 1 | - | | ||
| + | |24820-78|STUD \\ 5/16"-18 x 5/16-18| 2 | 24818-52 | | ||
| + | |27077-78|GASKET| 2 | - | | ||
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| + | 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. \\ | ||
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| + | 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. \\ | ||
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| + | Here are some part numbers for the different insulator blocks used on 4 stroke Harleys. \\ | ||
| + | There is no known insulator block that was factory installed on a Bendix Carb. \\ | ||
| + | |||
| + | * 27412-57 for 57-65 XL FL, FX. (Linkert) | ||
| + | * 27015-66 for XLH 66-71.XLCH '66;70-71 (Tillotson) | ||
| + | * 27012-67 (has 1 longer stud) 66-69 XLCH67-70 BTs (Tillotson) | ||
| + | * 29250-78 for 76-89 BTs (Keihin butterfly) | ||
| + | * 29250-78A for 78-E84 FL,FLH and Late 78-E84 FLT and 80-85 FXR (Keihin butterfly) | ||
| + | * 27003-86 for 86-87 XL (Keihin butterfly) | ||
| + | * 27003-86A for 86-87 XL (Keihin butterfly) | ||
| + | * 29266-86 plastic, for 86-87 XL (Keihin butterfly). | ||
| ====== Swapping to a Keihin CV Carb ====== | ====== Swapping to a Keihin CV Carb ====== | ||
| See [[techtalk:ref:carb09|Ironhead - Installing a Keihin CV Carb]] in the REF section of the Sportsterpedia. \\ | See [[techtalk:ref:carb09|Ironhead - Installing a Keihin CV Carb]] in the REF section of the Sportsterpedia. \\ | ||
