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techtalk:ih:carb01r [2020/04/01 20:08] hippysmack [IH: Carburetor, Intake Manifold & Exhaust - Sub-01R] |
techtalk:ih:carb01r [2020/08/03 20:59] hippysmack [Heat Spacer] |
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| - | ====== IH: Carburetor, Intake Manifold & Exhaust Systems - Sub-01R ====== | + | ====== IH: Carburetor, Intake Manifold & Exhaust - Sub-01R ====== |
| ====== Keihin Butterfly Carb (non CV) Functions, Adjustments, Tuning ====== | ====== Keihin Butterfly Carb (non CV) Functions, Adjustments, Tuning ====== | ||
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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. \\ | ||
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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. \\ | ||
| ====== Vacuum Ports (83-up) ====== | ====== Vacuum Ports (83-up) ====== | ||
