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hi I'm Lois Alice program manager for walbro and I'm Don Ross lawn and garden business unit manager this video is intended to help you inspect in-service walbro diaphragm carburetors whether the butterfly or rotary valve models as you know down a lot of changes in our industry have affected carpet or service the introduction of ethanol into our fuels affects the carburetor operation and tamper resistant features limits the amount of adjustment and users can make to the carburetors today we're going to discuss these topics along with the inspection and service of diaphragm carburetors in this video a basic understanding of the carburetor function will be very handy for this video so let's start there the carburetor does three important tasks first fuels drawn from the gas tank into the carburetor second the fuel is metered to match the engines RPM and load requirements and finally the metered amount of fuel is mixed with air and delivered to the crankcase at the proper time and the engines operating cycle to control the flow of fuel and air into the engine the carburetor uses pressure created within the engines crankcase known as an impulse the movement of the piston creates two types of impulses a negative impulse or vacuum is created during the Pistons upward stroke while a positive impulse is generated by the Pistons downward motion these impulses are delivered to the carburetor through machine channels in a manifold or impulse fitting the channels or fittings lead to the fuel pump the carburetor throat contains the throttle valve and in some models the choke bell that's good louie but if I think I've got a carburetor problem where do I start Don whenever you have a carburetor of any type that seems to be malfunctioning you first want to eliminate any potential causes that are not directly related to the carburetor always use fresh fuel based on the engine manufacturers recommendation engine problems resulting from bad spark plugs a clogged muffler or low compression can also be misinterpreted as carburetor problems so be sure to include these areas in your initial engine inspection procedures then check the fuel tank vent and the fuel filter for obstructions debris in either area could easily cause a fuel delivery problem if the filter is dirty clean or replace it with an original walbro fuel filter if the tank and vent are clear disassemble and inspect the air filter because carburetors depend on an adequate airflow a clogged filter could result in an overly rich condition next check the fuel and primer lines be sure they aren't pinched plugged or cut your initial inspection should also include a pressure check of the fuel line and the carburetor pressure testing the carburetor reveals the operating condition of the inlet needle connect your walbro pressure tester part number 57 - 11 to the fuel line apply air pressure by slowly depressing the plunger the gauge will indicate an increase in pressure until in the end let needle valve unseats this level is referred to as the Popoff pressure and may range from 15 to 50 psi due to the variety of carburetor design specifications occasionally the inlet needle valve will not on see in this case you'll need to disassemble the carburetor which we'll get into in just a bit after popping off the gauge will drop to indicate the pressure at which the inlet valves receipts this is referred to as the receipt pressure the inlet needle should reseat and hold a minimum of 5 psi complete the pressure check by performing the same test at the carburetors fuel Inlet if pressure tests show proper needle operation it's time to check the carburetor mounting area and the manifold and gasket connecting the carburetor to the engines crank case for wear damage be sure to inspect the impulse passage leading to the fuel pump chamber crankcase impulses must be able to reach the carburetor for it to operate properly to test put a drop of oil over the passage crank the engine a few times and watch the oil if the oil doesn't move or only move slightly the passage is blocked it must be cleared if the engine you're working on has a reed valve check the valve it should be free of debris and properly aligned with the intake port we should note that everything we've talked about so far applies to all types of diaphragm carburetors but now we want to look specifically at servicing the two major types of walbro diaphragm carburetors that are used in handheld equipment walbro manufactures a variety of butterfly valve carburetor models yet their components are all very similar let's see how a butterfly valve carburetor functions the butterfly valve carburetor can be divided into three basic areas of operation the fuel pump the fuel metering area and the throttle and choke valve the fuel pump is made up of a cover a gasket a diaphragm and the pump side of the carburetor body the pump is activated by crankcase impulses delivered through a machine channel or an impulse fitting the metering side also includes a fuel Inlet screen the inlet needle orifice the inland needle and the fuel metering chamber the meter and chamber is made up of a cover a metering diaphragm a gasket a metering lever pin and spring and nozzle check valve and the idle assembly located within the carburetor body and the idle adjustment screw the final area of operation includes the choke and throttle valve assemblies the throttle valve assembly is made up of a shaft lever assembly spring and valve the choke is made up of a shaft and lever assembly choke friction ball spring and a valve the amount of fuel delivered in the crank case is determined by the position of the throttle valve the more open the valve the more airflow the more air flow the greater amount of fuel delivered to the crank case well Louie that's a lot of good information it is down because a basic understanding of the butterfly valve carburetors function will come in handy as we inspect it for proper operation so let's get started and get into the proper procedure for inspecting the butterfly valve carburetor before you begin inspecting the carburetor be sure the metering and fuel pump areas are completely disassembled idle progression holes have been machined into the carburetor body these passages are accessible through a welsh plug to remove the welsh plug use tool number 500 - 16 available in both the 400 - 595 and 500 - 500 walbrook toolkits position the sharp end of the tool at a slight angle and tap the tool until it penetrates the welsh plug then apply light pressure to the handle until the plug pops out be careful not to contact or damage to carburetor body with the tool once the carburetor is disassembled clean the entire body and its covers use mineral spirits to avoid damage to carburetor parts and blow a drive with approximately 25 psi of compressed air be sure all holes and passages are clear on models with a check valve that has a nozzle feed hole you can verify the nozzle check valves operation with a small holes or fuel line position the holes our fuel line over the meter and chamber side of the nozzle then draw the nozzle check valve up against the retainer two or three times to ensure its operating properly do not use a metal tool to clear the nozzle now we can reassemble the carburetor beginning by installing the Welsh plug using tool number 500 - 15 align the welsh plug in position the tool on the dome part of the plug then tap the plug until it becomes flat it's important that the plug is flat so it doesn't interfere with the function of the metering diaphragm assembly moving in the past I remember using nail polish to seal the wall plugs the Istana is true however because of ethanol fuels we no longer use fingernail polish or any kind of sealing on the Welsh post we found that ethanol fuels can dissolve the seal and and create other problems now we can reassemble the inlet needle metering lever pin spring and lever pin screw next check the lever height adjustment with wall bros metering gage number 500 - 13 position the gage across the carburetor body the gauge should just contact a metering lever without opening the needle valve if the lever is misaligned use a small screwdriver to keep the head of the inlet needle stationary at the same time slide another small screwdriver to lift or depress the metering lever arm until it's properly adjusted this would be a good time to check the function of the inlet needle with the metering cover and metering diaphragm assembly removed apply pressure to the fuel Inlet fitting and manually depress the metering lever to ensure that the inlet needle moves freely if it doesn't disassemble the metering system completely and carefully clean the parts walbro small parts cleaner part number 500 - 520 will help you clean these parts carefully inspect the needle tip and the non-service will see for debris or damage before reassembly if you're working on an older carburetor with a circuit plate design inspect the circle plate and gasket for signs of damage or wear the holes in the circle plate should be free of any obstructions next replace the metering diaphragm and gaskets using original wall probe parts but we understand that the likelihood of damage to soft parts in the carburetor is greater with ethanol fuels right down while walbro continues developing advanced engineering materials that are highly resistant to ethanol ethanol fuels can affect soft parts like diaphragms fuel pumps and gaskets on all carburetors plus ethanol tracks moisture causing corrosion of the aluminum parts and moisture in the fuel also reduces its shelf life so how can we avoid problems first use the fuel recommended by the engine manufacturer second make sure it's fresh and finally run the fuel out of the equipment if it's going to be six weeks or more before you use it again great tips Louise thanks let's continue our butterfly valve carburetor inspection reassemble the fuel pump beginning with a new fuel Inlet screen fit the new screen into the screen pocket and press to the screen pocket step using walbro tool number 500 - 15 the screen should completely contact the casting wall next reassemble the pump diaphragm gasket pump cover and cover screw if any of the carburetor components are damaged replace them with original walbro parts a generic exploded view and a list of all the carburetors specific parts can be found at Walker's website at wwlp.com before reinstalling pressure test the carburetor as we discussed in the initial inspection section to ensure it has been properly reassembled if the carburetor passes the pressure test it can now be reinstalled on the engine and check for proper adjustment the way I understand the carburetor adjustment procedures have changed to accommodate newer carburetors with tamper resistant features that's right due to environmental concerns since the mid-90s carburetors have come equipped from the manufacturer with tamper resistant features of various kinds these features limit the amount of adjustment available to consumers in order to maintain low emissions the tools techniques and specifications needed to adjust these carburetors are available to authorized dealers directly from the engine manufacturer however resale these tools to consumers carries heavy penalties on all carburetors tamper resistant or not you can still adjust the idle speed screw refer to the manufacturers recommendations for settings that covers the operation troubleshooting and adjustment of wall rope butterfly valve carburetors further servicing information and an ample supply of original replacement parts can be obtained at your wall Road distributor walbro manufacturers various versions of rotary valve carburetors will the carburetors differ somewhat design the components can still be grouped into three basic areas of operation the fuel pump the metering area and the throttle shaft assembly most of these carburetors also come equipped with their own primer let's take a closer look at the components that make up the rotary valve carburetors three functional areas and their attachments the first functional area includes the fuel pump found beneath the primer pump assembly the fuel pump is made up of a gasket a diaphragm pump body assembly and the pump side of the carburetor body removing these components also reveals a fuel Inlet screen and an inlet needle orifice the carburetor body also contains a channel which allows crankcase impulses to enter the fuel pump the metering area is made up of the inlet needle seat the main nozzle check valve a metering diaphragm assembly the metering lever pin spring and the inlet needle the inlet needle is held in the closed position by the force of the spring against the lever some rotary valve carburetors may contain a serviceable main jet the final area of operation is the throttle area the rotary throttle barrel assembly includes the barrel valve needle spring throttle ramp idle screw bracket idle adjustment screw swivel and throttle lever most of Waldo's rotary valve carburetors come equipped with a priming system these systems are designed to purge the system of air and assist the carburetor during startup the primer is made up of the purge body assembly cover and primer bulb and a number L check valve that controls the flow of fuel and air during the priming operation depressing the primer bulb opens the outlet check valve allowing air and fuels to exit the ball as the ball returns to shape a vacuum is created opening the fuel inlet valve causing fuel to circulate throughout the carburetors fuel circuit and into the bulb under most circumstances the bulb should only have to be depressed four to five times to properly prime the system to inspect rotary valve carburetors begin by performing an initial general inspection of the areas surrounding the carburetor including air filter muffler spark plug fuel filter and fuel holes if no problem is found the carburetor must be disassembled as you disassemble the carburetor note the order in position of the components this will help you correctly reassemble the carburetor after it's been inspected start the disassembly procedure at the primer pump assembly just below the primary assembly is the metering area which consists of a metering diaphragm assembly a gasket and the metering lever pin spring and inland needle leave the inlet needle lever pin and spring assembled within the pump body assembly unless they require replacement removing the fuel pump body is also the first step in disassembly in the fuel pump the fuel pump consists of the body a diaphragm a pump gasket and the fuel pump side of the carburetor the pump body assembly contains a fuel Inlet screen and the inlet needle orifice the fuel pump side of the carburetor body also contains the main jet and its own ring once the carburetor is completely disassembled clean its metal components using mineral spirits now that you finish cleaning up components it's time to reassemble the carburetor begin by reassembling the main jet will ring and main jet into the pump side of the body install the fuel Inlet screen into the fuel pump cover using tool number 500 - 15 the screen should be pressed to the screen pocket step and fit flush with a pocket wall reassemble the meter area using original walbro parts you check the lever height adjustment with wall bros meter engage number 513 and adjust as needed you have the option of replacing the entire fuel pump by the assembly as a replacement unit this simplifies replacement and eliminates the need for the meter and lever height adjustment now reassemble the fuel pump body assembly to the pump side of the carburetor body using a new gasket and diaphragm the final area to inspect and reassemble is the primer pump assembly reassemble using the gasket diaphragm purge body bulb and cover if the primary pump valve doesn't seat properly or the primer bulb doesn't return to shape replace the entire primer pump assembly once you have completely reassembled the carburetor it must be pressure tested again the procedure is the same as we use in the initial inspection and also for the butterfly valve carburetors using your wall probe pressure tester number 57 - 11 determine the valves Popoff and reseed pressure settings be sure the inlet needle valve is wet before you pressure test it the gauge will indicate an increase in pressure until the inlet needle valve unseats the inlet needle should unseat between 15 to 60 psi depending upon the carburetors design specifications this level is referred to as the Popoff pressure the gauge will then drop to indicate the pressure where the inlet legal valve receipts this is also referred to as the receipt pressure the valve should receipt at a minimum of 5 psi if the carburetor passes the pressure test that can be reinstalled on the engine and check for proper adjustment as we discussed with butterfly-valve carburetors carburetor adjustment procedures are different now because newer carburetors have tamper resistant features that's right since the mid 90s car breeders have come equipped from the manufacturer with tamper resistant features of various types these features are designed to limit the amount of adjustment possible by consumers if you're an authorized dealer the tools techniques and specifications necessary to adjust these carburetors are available from the engine manufacturer however these cannot be solved consumers without the risk of heavy fines on all carburetors Tampa resistor or not you can adjust the idle speed screw just refer to the engine manufacturers recommendations for these settings congratulations this concludes the operation repair and adjustment of walbro rotary valve carburetors for more information on servicing walbro diaphragm carburetors the location of your nearest authorized walbro distributor and other information about walbro and its products visit our website at www.fiberlinecommunications.com