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SERVICE TRAINING PROGRAM ON UCD CARBURETTOR FOR ROYAL ENFIELD LIMITED (REL)



By UCAL FUEL SYSTEMS LTD, CHENNAI



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CARBURETTOR ASSEMBLY



REL CODE: 570282/h



UFSL CODE: BS29-19 APPLICATION: REL 350 cc All models



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FUNCTION OF THE CARBURETTOR Carburetor performs 3 important functions:  Varies the air-fuel (A/F) ratio according to various operating condition of the engine.  Produces atomized air-fuel mixture. Atomization is the mixing of air and fuel to form a fine droplets.  Regulates the amount of air-fuel mixture required by the engine.



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FUNCTION OF THE CARBURETTOR Proper Air / Fuel ratio gives:



 Maximum combustion efficiency.  Reduction in the formation of polluting gases.



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CARBURETTOR WORKING PRINCIPLE • In constant depression carburettor driver controls the throttle valve. • Piston valve (PV) moves in direct proportion to the engine demand. • PV movement assures correct venturi size and air velocity throughout the midrange operation of the engine



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CARBURETTOR WORKING PRINCIPLE • PV movement is accomplished with a rubber diaphragm attached to the top of the PV • Diaphragm separates two chambers. • Chamber below the diaphragm vented to atmosphere. • Chamber above the diaphragm exposed to venturi air pressure. • Piston valve lifting is possible by the differential pressure occurring between the two chambers.



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VARIOUS SYSTEMS OF CARBURETOR 1. FUEL INLET AND FLOAT SYSTEM 2. STARTER SYSTEM



3. PILOT SYSTEM(SLOW SPEED SYSTEM) 4. MAIN SYSTEM(HIGH SPEED SYSTEM)



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1.FUEL INLET AND FLOAT SYSTEM



FUEL INLET



VIEW BOWL



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1.FUEL INLET AND FLOAT SYSTEM • Consists of: Fuel Inlet Bowl Float Needle assembly



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1.FUEL INLET AND FLOAT SYSTEM • Fuel from tank enters in to the bowl through fuel inlet nipple. • Fuel level in the bowl must be high enough to reach Pilot, main and starter systems. • The fuel level in the bowl is maintained by the float system • A higher fuel level will richen the mixture causing excessive fuel consumption and poor running. • Low fuel level will cause leanness which may result in flat spot, engine over heat and seize. 01-MAR-2013



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2.STARTER SYSTEM • At cold condition, engine parts are not hot enough to vaporize the fuel. • So rich mixture is required at cold conditions. • Rich mixture is provided by starter system.



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2.STARTER SYSTEM



VIEW



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2.STARTER SYSTEM Starter System consists of: Starter jet : Meters the fuel Emulsion tube :Long tube with small holes drilled at sides. Starter Plunger. Air passage and mixture passage.



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2.STARTER SYSTEM • Starter jet meters the fuel.



• Starter plunger is lifted by a cable or a lever. • Lifting of starter plunger causes: Uncover the fuel passage that leads to the starter jet. Uncovers the air-inlet passage and the outlet to the manifold.



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2.STARTER SYSTEM • At idle condition (Throttle valve in full closed condition) almost all the air that goes to the engine pass through the starter passage. • This creates enough suction to draw fuel up from the bowl into the chamber below the plunger. • Fuel is mixed with the air in this chamber and drawn to the engine. • Atomization of the mixture is aided by an emulsion tube. • The purpose of its atomization is to foam the fuel slightly allowing it to flow more easily through the small passage



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3.PILOT SYSTEM (SLOW SPEED SYSTEM)



BYPASS PORTS



VIEW1 VIEW2 VIEW3



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3.PILOT SYSTEM (SLOW SPEED SYSTEM) • Pilot system consists of: Pilot Jet (PJ): To meter the fuel Pilot air jet (PAJ): To meter the air volume.



Pilot screw: To control the amount of air fuel mixture flowing through the pilot outlet (PO). Bypass holes



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3.PILOT SYSTEM (SLOW SPEED SYSTEM) • At idling condition (Throttle valve full closed) mixture to the engine is supplied mainly through PO and bypass hole #1 • At low speeds mixture is supplied mainly through the bypass holes and PO. • Mixture will become lean when Pilot screw is tightened (Turned CW) and rich when loosened (Turned CCW).



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4.Main system Diaphragm



Piston Valve



Jet needle Needle Jet Main Air Jet



VIEW1 VIEW2



Main Jet



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4.Main system • Main system consists of: Main Jet : Meters the fuel. Jet holder : Aids the emulsification process Jet needle : Taper in the needle provides a



variable clearance with the needle jet for varying speeds. Needle jet : Orifice Diameter to control the fuel flow` 01-MAR-2013



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DIS-ASSEMBLING PROCEDURE • Unscrew the top cover and remove the piston valve assembly and spring from the carburettor. • Remove the ring and diaphragm from the piston valve. • Generally, it is not advisable to remove the jet needle. If it is necessary, unscrew the jet needle fixing plate screws and remove the jet needle along with the spring. • Unscrew the starter guide holder assembly by using the right size spanner and remove the plunger along with the spring. • Unscrew the mixture control screw along with its spring, plate washer and o-ring. 01-MAR-2013



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DIS-ASSEMBLING PROCEDURE (Cond..) • Unscrew the float body fixing screws and remove the float body from the mixing body.



• If it is absolutely necessary, unscrew the float toggle pin retaining screw and remove the float along with the needle valve. • Unscrew the pilot jet, main jet and main jet holder from the mixing body. • Remove the needle jet from the mixing body only if it is necessary. • Unscrew the drain screw from the float body. • Unscrew the pilot air jet from the mixing body if. 01-MAR-2013



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ASSEMBLING PROCEDURE • Follow the reverse sequence of dismantling procedure. • While assembling the jet needle ensure that the jet needle ring pin coincides with the corresponding hole in piston valve. • When fixing the needle jet ensure that the correct concentricity to main jet holder hole is maintained.



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MAINTENANCE • The maintenance of the carburettor is merely a question of cleaning periodically in order to avoid blockage of jets and passages. • Maintaining a full tank of petrol doesn’t allow fuel tank to rust and there by reduces rust deposits in the carburettors. • Drain the carburettor every three thousand kms by removing the drain screw to drain all the deposits at the bottom of the float bowl. • When using the choke do not open the throttle as it may cause flooding. • Clean Air-filter regularly, as a blocked or damaged air-filter will have an adverse effect on both the carburettor as well as the engine performance. 01-MAR-2013



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SERVICE GUIDELINES • Spray the carburettor cleaner in all passages to ensure that there is no blockage due to dust, dirt gum or carbon deposit, especially in the main air passage, pilot air passages, including by pass holes and pilot outlet • While re-assembling dismantled carburettors, always replace the old gaskets and o-ring with new ones. • Cleaning of jets should be done only with the help of carburettor cleaner and compressed air. • Check the float height and ensure that it is as per specifications.



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SERVICE GUIDELINES (Cont..) • Ensure that the pilot jet is not tightened beyond the specified torque as this will cause the head to shear and removal of the jet from the mixing body becomes nearly impossible.



• Do not tamper with the e-ring position of the jet needle or change the sizes of the jets in order to attain better mileage or power as this will have adverse effect on the engine performance and lead to pre-mature wear of engine parts. • Ensure that the seating area of the choke plunger assembly is not worn or damaged. If worn or damaged, replace the plunger assembly.



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SERVICE GUIDELINES (Cont..) • Always use genuine parts, of the right specifications, for replacements. • Tighten all screws & jets to the right specifications.



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SERVICE GUIDELINES (Cont..) TIGHTENING TORQUE SPECIFICATION:



PILOT JET



: 8 ± 2 kgf-cm



MAIN JET



: 18 ± 5 kgf-cm



BOWL FIXING SCREW



: 35 ± 10 kgf-cm



DRAIN SCREW



: 20 ± 5 kgf-cm



STARTER GUIDE HOLDER



: 25 ± 5 kgf-cm



TOP CAP SCREW



: 35 ± 10 kgf-cm



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FAULT DIAGNOSIS & RECTIFICATION PROCEDURE PROBLEM



CAUSE Clogged starter circuit



Clean starter circuit with carburettor cleaner



Pilot jet clogging



Clean jet with spray/replace it if necessary



Low fuel Level



Check float for damage and float height.



Flooding



Check float for damage or float height.



Pilot jet clogging



Clean jet with air/replace it if required



Incorrect pilot screw setting.



Adjust pilot screw as per specification.



Improper fitment of carb



Ensure correct fitment.



High/Low fuel level



Adjust float height to spec.



Piston valve sticky



Clean piston valve/mixing body and ensure no damage in piston valve and diaphragm.



STARTING TROUBLE



IDLING NOT STABLE



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RECTIFICATION



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FAULT DIAGNOSIS & RECTIFICATION PROCEDURE (Cont..) PROBLEM



FLOODING



POOR PICKUP



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CAUSE



RECTIFICATION



High fuel level



Adjust float height to spec.



Improper seating of needle valve in valve seat



Clean needle valve/replace if necessary.



Float puncture



Replace float.



Main / pilot jet clogged



Clean / replace



High/Low fuel level



Adjust float height to spec.



Incorrect E-ring position in Jet needle.



Assemble E-ring in correct position



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FAULT DIAGNOSIS & RECTIFICATION PROCEDURE (Cont..) PROBLEM



POOR MILEAGE



CAUSE



RECTIFICATION



Clogging of main air / pilot air circuit.



Clean with carburettor Cleaner



High fuel level.



Adjust float height to spec.



Incorrect E-ring position.



Assemble E-ring in the correct notch.



Clogging of fuel hose coming from fuel tank



Change the fuel hose



Clogging of fuel inlet nipple



Remove the dust with small needle and clean with air



Clogging of pilot jet.



Clean with carburettor Cleaner



Part missing



Check the presence of Ball plugs and Air jets



BLOCKING OF FUEL



MISFIRE



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FACTORS AFFECTING MILEAGE OTHER THAN CARBURETTOR  Set the tyre pressure according to the manufacturers specification as low tyre pressure will result in excess fuel consumption.  Check air cleaner as duty air cleaner will have adverse effect



on the fuel consumption.  Check for brake binding.  Check for valve clearance for the four stroke engine and set it



to the manufacturers specification.  Check the condition of spark plugs.  Check for leakages at fuel tank, Fuel cork, Intake manifold and



at Carburettor fitments. 01-MAR-2013



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CARBURETTOR SETTING



MAIN JET



: #110



PILOT JET



: #12.5



NEEDLE JET



: P-2M (922)



JET NEEDLE



: 4DHL42-2/3



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NEW PRODUCT FOR BULLET 500cc



REL CODE: 570889/d



UFSL CODE: UCD33-X5 APPLICATION: REL Bullet 500 cc Model



CHANGES IN UCD33 CARBURETTOR  ROTARY TYPE TPS (CTS MAKE) USED IN UCD33 CARBURETTOR



 IT PROVIDES OUTPUT VOLTAGE WRT THROTTLE POISITION TO TCI UNIT  WITH ROTARY TPS,IT IS POSSIBLE TO MAP THE IGNITION TIMING WRT THROTTLE OPENING/LOAD



TPS REPLACING PROCEDURE  HOLD THE CARBURETTOR AS THE TPS SIDE IS FACING YOU (REFER PICTURE )  LOCATE & REMOVE THE TPS FIXING SCREW WITH THE APPROPRIATE TOOL. (T25 HEAD TYPE)  DURING LOOSENING THE SCREW, TAKE CARE NOT TO DAMAGE THE SCREW HEAD.  REMOVE THE TPS FROM THE CARBURETTOR WITH HAND.



TPS fixing screw



TPS



TPS REPLACING PROCEDURE  CLEAN THE TPS HOLDING HOLE IN THE BODY (PICTURE 1) AND THE SHAFT (PICTURE 1).  ASSEMBLE THE NEW TPS INTO THE BODY SUCH THAT THE BOSS 'D' (REFER PICTURE 2) IS HELD IN THE BODY HOLE ( REFER PICTURE 1) AND THE SLOT (REFER PICTURE 2) IN THE TPS IS INSERTED IN THE SHAFT ( REFER PICTURE 1)



Picture 1 Shaft



TPS holding Hole in body Screw fixing slot



Slot Picture 2



D



TPS REPLACING PROCEDURE  AFTER ASSEMBLING THE TPS THE POSITION OF THE TPS SHOULD BE AS SHOWN THE PICTURE.  CONNECT THE TPS AS PER THE BELOW CIRCUIT AND ROTATE THE TPS SLOWLY SUCH THAT THE IDLE OUTPUT VOLTAGE IS 0.7 ±0.05 V.



TPS position before fastening the screw



TPS REPLACING PROCEDURE  FASTEN THE SCREW TEMPORARILY AND CHECK THE OUTPUT, CONFIRM THE SPECIFICATION AND FASTEN THE SCREW TO A TORQUE OF 3.5±1.0 N-M.  ENSURE THAT THE TPS DOES NOT ROTATE FREELY



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FAULT MISFIRE:



•Carbon deposit- Lean mixture / Engine manifold leak/ Air entry thro air cleaner side •Lean mixture- Pilot circuit blockage/ PAJ Missing/



•Improper ignition timing •MJ loose •Fuel level low



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