Filed Under (Triumph) by admin on 20-11-2010
1. The Float The float bowl acts as a fuel reservoir to meet engine demand. The float is hinged on a pin in the float boss. It rises and falls with the fuel level in the float bowl. The small metal tang integrated in the plastic float supports the float valve, also known as the float needle. As the fuel in the float bowl rises, the float valve is pushed into the valve seat, until it’s high enough to shut off the fuel flow to the bowl. As fuel is used the level in the bowl drops lowering the float which pulls the float valve from its seat, and fills again. Adjusting the height of the float has a big effect on the mixture as a low or high float level makes it harder or easier for the vacuum to suck fuel into the venturi. Differing float levels cause an imbalance which may be perceived as vibration. 2. The Choke This system is referred to as the choke. But that’s a misnomer. When you pull the choke knob, what you’re doing is retracting a plunger that opens a tube connected to the starter jet, allowing additional fuel to enter the venturi just below the vacuum hose nipple. It supplements the pilot system at start up. 3. The Pilot System The primary purpose of the pilot system is to supply the mixture at idle. It continues to supply fuel throughout the entire throttle range, but after about 1/8 throttle is reached the main system starts to put out more of the total mixture, up to full throttle. By adjusting the idle with the big screw on the left side of the carburettors the position of the butterfly is altered, so exposing one or more of the four small holes that are drilled into the venturi, (leading to the pilot jet) just under the butterfly valve, letting more or less air pass the butterfly. Adjusting the pilot screw that’s under the carburettor varies the amount of air premixing with the fuel before it enters the venturi. 4. The Main System Open the throttle and the cable that’s connected to the butterfly valve turns it from vertical to horizontal, so letting more air through the venturi. This increases the vacuum effect that is transferred up through the vacuum drilling in the slide to the diaphragm valve that leads to the diaphragm chamber. The top chamber is separated from the bottom by a rubber diaphragm. The bottom chamber is open to atmospheric pressure from the airbox. When the vacuum in the top chamber rises enough, the constant ambient pressure of the lower chamber helps the diaphragm valve overcome the downward force of the diaphragm spring, so it rises from the ven- turi. As the diaphragm is raised the needle is pulled out of the needle jet, exposing a thinner portion of the needle taper which allows more fuel to rise into the venturi to meet the increased engine demand. The key parts of the main system are shown in the photo below
Filed Under (KTM) by admin on 12-11-2010
Carburetor adjustment Basic information about the original carburetor setting The original carburetor setting was adapted for an altitude of approx. 500 meters (1600 ft.) above sea level, and the ambient temperature of approx. 20°C (68°F), mainly for off-road use and central European premium-grade fuel (ROZ 95). Mixing ratio 2-stroke motor oil : super fuel 1:40 . Basic information of changing the carburetor setting Always start out from the original carburetor setting. Essential requirements are a clean air filter system, air-tight exhaust system and an intact carburetor. Experience has shown that adjusting the main jet, the idling jet and the jet needle is sufficient and that changes of other parts of the carburetor will not greatly affect engine performance. RULE OF THUMB: high altitude or high temperatures choose leaner carburetor adjustment low altitude or low temperatures choose richer carburetor adjustment * WARNING * -ONLYUSE PREMIUM – GRADE GASOLINE ROZ 95 MIXED WITH HIGH – GRADE TWO – STROKE ENGINE OIL . OTHER TYPES OF GASOLINE CAN CAUSE ENGINE FAILURE , AND USE OF SAME WILL VOID YOUR WARRANTY . -ONLYUSE HIGH – GRADE 2- STROKE ENGINE OIL OF KNOWN BRANDS ( I . E .SHELL ADVANCE RACING X). -NOTENOUGH OIL OR LOW – GRADE OILCAN CAUSE EROSION OF THE PISTON . USING TOO MUCH OIL , THE ENGINE CAN START SMOKING AND FOUL THE SPARKPLUG . -INTHE CASE OFA LEANER ADJUSTMENT OF THE CARBURETOR PROCEED CAUTIOUSLY . ALWAYSREDUCETHEJETSIZEINSTEPSOFONENUMBERTOAVOID OVERHEATING AND PISTON SEIZURE . NOTE: If despite a changed adjustment the engine does not run properly, look for mechanical faults and check the ignition system. Basic information on carburetor wear As a result of engine vibrations, throttle valve, jet needle, and needle jet are subjected to increased wear. This wear may cause carburetor malfunction (e.g., overly rich mixture). Therefore, these parts should be replaced after 1000 hours of using. Idling range – A Operation with closed throttle valve. This range is influenced by the idle adjusting screw 1 . Only make adjustments when the engine is hot. The idling speed can be changed by turning the idle adjusting screw. Turning it clockwise produces a higher idling speed and turning the screw counterclockwise produces a lower idling speed. Opening up – B Engine behavior when the throttle opens. The idle jet and the shape of the throttle valve influences this range. If, despite good idling-speed and part-throttle setting, the engine sputters and smokes when the throttle is fully opened and develops its full power not smoothly but suddenly at high engine speeds, the mixture to the carburetor will be too rich, the fuel level too high or the float needle is leaking. Part-throttle range – C Operation with partly open throttle valve. This range is only influenced by the jet needle (shape and position). The optimum part-throttle setting is controlled by the idling setting in the lower range and by the main jet in the upper range. If the engine runs on a four-stroke cycle or with reduced power when it is accelerated with the throttle partly open, the jet needle must be lowered by one notch. If then the engine pings, especially when accelerating under full power at maximum engine revs, the jet needle should be raised. If these faults should occur at the lower end of the part throttle range at a four-stroke running, make the idling range leaner; if the engine pings, adjust the idling range richer
Filed Under (Mikuni) by admin on 31-10-2010
Intake Manifold: 1. Install MAP sensor in Mikuni manifold (Twin Cam only). 2. Attach the Mikuni manifold to the engine. Align the manifold before tightening the bolts. The flange surface of the Mikuni manifold should be parallel with the front of the engine’s cam cover. Use a level or angle meter to check this. Tighten the manifold bolts. 3. Attach the rubber flange to the Mikuni manifold with the furnished 5/16″x3/4″ bolts and washers. Choke Cables: Mikuni & Harley-Davidson Route the cable with largest radius bends possible. Check the cable for free-play after installation. If there is no free-play, the engine may run rich and deliver poor performance or low fuel mileage. Harley Cable (Twin Cam Kits: 42-19, 45-4) : 1. Remove the Harley choke cable from the stock carb. 2. Remove the spring and plunger from the cable. 3. Remove the spring and plunger from the Mikuni. 5. Install the Mikuni spring and plunger onto the Harley choke cable. Change nothing else; be sure to use the Harley plastic nut, not the Mikuni nut (See Figure 1). Total Kit Installation Instructions The HSR series carburetors are precise yet durable instruments; however, like any other piece of fine equipment, they require correct installation and reasonable care to assure optimum performance and long life. Extra time spent during installation will pay off in both short and long term performance and reliability. This Mikuni HSR carburetor kit is designed to be a bolt-on application, and as such, is set-up and jetted properly for most applications. However, since Harley-Davidson motors are often highly modified, alternate tuning settings may be required. The Mikuni Tuning Manual helps make jetting alterations and adjustments an easy matter. NOTE: Carburetor Kits not designated as C.A.R.B. exempt, are not legal for motor vehicles operated on public highways in the state of California, or in any other states and countries where similar laws apply. WARNING NOTE: NOTE: WARNING CAUTION NOTE: NOTE: TK-2 6. Install the new assembly into the Mikuni carburetor. Be careful to only gently tighten the plastic nut. 7. Loosen the knurled plastic friction nut behind the choke knob and check for free-play (see Figure 2). Figure 1: Harley nut with Mikuni spring & plunger Figure 2: Choke cable adjustments Mikuni Cable (Evo Kits: 42-8, 45-2 & 45-3) : 1. Remove nut, spring and plunger from the Mikuni. 2. Install the nut, spring and plunger onto the cable. 3. Install the assembly into the Mikuni HSR carburetor. Be careful to only gently tighten the plastic nut. 4. Check for free-play. Adjust the cable as necessary. An optional choke cable mounting bracket is included in the Evo kits for custom installations. Carburetor Installation: 1. Insert the carb fully into the rubber flange, align with engine and tighten the clamp. 2. Slip the fuel hose onto the carburetor’s fuel fitting and secure with the enclosed hose clamp. NOTE: Some Twin Cam installations may require removal of a small amount of fin material from the cylinders to clear the float bowl. Throttle Cables The HSR carburetor uses stock 1990 and later Harley- Davidson cables. However, if your Harley is fitted with some other carburetor, you may need to purchase a set of cables. See your dealer for the correct cable set. 1. Route the throttle cables with large radius curves and so they do not interfere with other components. 2. Screw the cable adjusters together to make them as short as possible. 3. Connect the “close” cable first (see Figure 3). 4. Install the “open” cable next (see Figure 3). 5. Adjust the opening cable until the slide can be opened fully. Snug the adjuster lock nut. 6. Turn the handlebar to the right and adjust the throttle free-play with the closing cable adjuster to approximately 1/8″ (see Figure 4)
Filed Under (Tips and Review) by admin on 11-11-2010
1. Make sure the ignition timing is correct 2. Adjust the valves as necessary to ensure proper operation 3. Run the engine to warm it up a bit 4. Adjust the float setting. To do this, remove the carburetors (leave the throttle cables attached), remove the bowl and turn the carburetor upside down (fuel will spill). The float should look like this: Adjust as necessary by bending the float support (#37 in Figure 1). Reinstall Installation and idle adjustment 1. First you must adjust the idle. It is acceptable per the manual to adjust the idle by using the idle adjust screws (11). This usually involves screwing them then backing out 1 to 1.5 turns. Or you can adjust looking at the sliders 2. If installing the carburetors: a. Remove the cover (2) b. Reomve the slider (3) c. Place the throttle cable through the guide (18) with the spring (4) on the cable. d. Route the cable through the slide catch (6) e. Insert the slide assembly into the chamber and make sure it easily slides up and down. Direct the needle (8) into the opening of the diffuser (angled side visible). f. Screw assembly together and verify via throttle movement that slide moves freely. Attach fuel delivery lines to (12). 3. Using the idle set screw (11) raise the slider so the lower edge is 1-2 mm. 4. Assemble to engine using the proper gaskets (paper – felt – paper). 5. Using the locknut (26) adjust the free play of the throttle cable (2-3 mm) 6. Adjust the idle mixture screw – turn in completely then out 1 to 1.5 turns. * Starting using the K68′s (cold weather) 1. Verify fuel flow. Apply choke (pull 52 in Fig1). 2. Using the ticklers (13) allow fuel to enter the bowl until fuel drains from (14) 3. With the ignition off, kick 1 or 2 times 4. Turn ignition on, and as soon as engine is warmed up (maybe sooner) push choke mechanisms to open choke Idle Adjustment (engine running and warm) 1. Remove one of the spark plug caps, and with the cap shorted, adjust (11) to decrease RPM’s to a point of being minimally steady. 2. Adjust the mixture (15) out until RPM’s decrease. Turn in until RPM’s increase slightly. Then turn in screws ¼ to 1/3 revoultion. 3. Do the same for the second carburetor with the first spark plug cap shorted. 4. With both cylinders, adjust each idle (11) on each carburetor the same amount each until it’s at a steady, minimal RPM. Use small changes. (at this point you can use your airflow tool to check). 5. Sharply increase, then decrease throttle. Then engine must return to low RPMs smoothly. If the engine goes below limits, readjust (11) from step 4. Synchronization of the K68 Note: Rather than using the opposite cylinder shorted to test the pull of the live cylinder carburetor, you can use something like a Twinmax connected to the test ports (27 Fig 1). Or, if you have a model without these ports, use a Synchrometer (Appendix 2) held against the face of the carburetor. These tools merely show airflow passing through each carburetor (which is dependent on the position and wear on the slide). If using these tools, it’s not necessary to do the following steps. You wil want to use a throttle guide (Appendix 1), to show airflow at various throttle settings. Using the flow meter of your choice make sure each carburetor is the same at the various throttle settings. 1. Place the motorcycle on the center stand ensuring the rear wheel is suspended 2. Make sure you have large area to work with (safety issues here) 3. Shift into the highest gear with the engine running 4. Short one spark plug cap to the cylinder (using a nail or something in the fins) 5. Increase the speed to 40-50 km/hr 6. Fix the throttle using the throttle (maybe using a throttle stop screw under the throttle housing). 7. Reconnect other cylinder and using the opposite carburetor determine the speed which should be the same as the first. 8. Adjust the position of this slide to achieve the referenced speed using the locknut at the top of the carburetor.
Filed Under (Harley Davidson) by admin on 26-03-2012
A. BEFORE INSTALLATION OF YOUR NEW ZENITH CARBURETOR, NSPECT THE RUBBER MANIFOLD SEAL FOR NICKS,CRACKS, OR DEBRIS. APPLYING A LIGHT FILM OF PETROLEUM BASED LUBRICANT AROUND THE INSIDE LIP OF THE RUBBER SEAL WILL ALLOW THE CARBURETOR TO SLIP INTO PLACE EASIER. B. BEFORE ACTUAL INSTALLATION OF UNIT INTO MANIFOLD, THROTTLE CABLES SHOULD BE HOOKED TO THETHROTTLEWHEEL.MAKESURETHATTHE PULL CABLE IS LOCATEDPROPERLY TO OPEN THE THROTTLE PLATE (IN SOME APPLICATIONS THROTTLE CABLE SLACK MAY NEED TO BE ADJUSTED FOR PROPER HOOKUP AND OPERATION) SEE FIG. #1 C. AFTER THROTTLE CABLES ARE PROPERLY HOOKED UP,UNITCAN BE INSERTED INTO MANIFOLD. MAKE SURE THAT UNIT IS FULLY SEATED. WITH CARBURETOR SEATED INTO MANIFOLD AND FUEL LINE HOOKED UP TO FUEL INLET, INSTALL CHOKE CABLE AND HOOK TO CHOKE LEVER. PLACE AIR INTAKE GASKET ON END OF CARBURETOR, NEXT PLACE INTAKE ADAPTOR OVER INTAKE GASKET. SEE FIG#2 ZENITH MOD.16P12 SPIGET MOUNT CARBURETOR -HARLEY DAVIDSON ™ BIG TWIN INSTALLATION INSTRUCTIONS FIG. # 1 FIG. # 2 D. WITH ADAPTOR IN PLACE, LOCATE THE STOCK AIR BOX OVER THE ADAPTOR, UTILIZING THE STOCK AIR BOX GASKET (THERESHOULDBENO GAPS BETWEEN ADAPTOR, AIRBOX OR CARBURETOR WHEN PROPERLY INSTALLED) STAND-OFF SPACERS PROVIDED ARE TOBEPLACEDBETWEENAIR BOX& ENGINE HEADS BEFORE INSTALLING THE VENT/RETAINING BOLTS. FOR EVALUATION ENGINES STOCK VENT BOLTS CAN BE USED WITH LARGERI.D. SPACER PROVIDED. SEE FIG#3 E. WITH AIR BOXSECURELY IN PLACE, INSTALL THE AIR FILTER COVER RETAINING BRACKET AND FILTER USING THE STOCKBOLTS, AND REPLACE AIR FILTER COVER AND SECURE WITH STOCK BOLT. SEE FIG#4 F. AFTER INSTALLATION IS COMPLETE AND FUEL FLOW HAS BEEN RE-ESTABLISHED, CHECK FOR ANY LEAKS BEFORE STARTING ENGINE. H. AFTER STARTING ENGINE, SOME ADJUSTMENTS OF IDLE AND MAIN JET MAYBE REQUIRED FOR PROPER OPERATION. AFTER ADJUSTMENTS HAVE BEEN MADE AND WITH ENGINEAT IDLE, TURN WHEEL FULLYTOLEFTANDRIGHT.ANYCHANGEIN IDLE SPEED INDICATES THROTTLE CABLES ARE TOO TIGHT AND MORE SLACK MUST BE PROVIDED.