TM33 Pumper Carburetor Upgrade For The Yamaha XT225 Installation Guide and Setup Instructions TM33 Kit Copyright 2004 ENDUCO, Inc. TM33 Installation Guide V1.
Introduction: This manual describes the TM33 pumper carburetor and explains how to install it on the XT225 Yamaha motorcycle. Please read the information carefully to avoid problems with the installation. The stock carburetor on the XT225 is a CV type. This means the carburetor’s slide is not under direct control of the throttle cable but is, instead, operated by vacuum built up by a butterfly valve which is controlled directy by the throttle cables.
Kit Contents: The TM33 kit contains the following items: 1 Mikuni TM33-8012 Pumper Carburetor* 1 Aluminum Cable Spacer 4’ 5/16” Drain & vent hose 1 16” piece of 3/16” drain hose 1 Instruction Manual (PDF file) 3 Nylon zip ties * The TM33 carburetor supplied in this kit has been modified to include a custom cable bracket and a special jet needle. DO NOT SMOKE AROUND GASOLINE TM33 Installation Guide V1.
Installing the TM33: Overview: Although the TM33 carburetor’s inlet and outlet flanges match those of the stock carburetor other dimensional and mechanical differences exist. The installation steps supplied in this manual account for this and explain how to make a neat and clean installation that’s easily reversible should it be necessary to restore the bike to stock condition. Please read these instructions carefully, use common sense and good judgement during the installation process.
Installing the TM33: (continued) STEP 2 (continued) with WD40 if required. If the bolt is stubborn, hold the strap with an adjustable wrench close to the threads. With the strap loose pull scoop panel pins from grommets then slide the scoop panels forward off the gas tank tabs. Small rubber grommets are on the gas tank tabs so make sure not to lose them. STEP 3 Remove the seat. Using the 10mm socket remove the two bolts on either side of the seat. These bolts are located just in front of the handles.
Installing the TM33: (continued) STEP 6 Remove the stock carburetor. Using the small flat wrench provided in your bike tool kit or small adjustable wrench loosen the throttle cable ends and disconnect them from the bell crank. a) Remove the starter enrichening lever (choke) bracket from the handle bars using a 12mm socket. Replace the handle bar bolt and tighten it. In the enrichener cable, there is a rubber boot (about 1/2 way down the cable).
Installing the TM33: (continued) STEP 8 Install aluminum cable spacer. Pull the rubber throttle cable boot away from the throttle grip as shown below. Disassemble the two halves of the throttle grip using a phillips head screw driver. Free the cable ends from the nylon drum. There are two right angle black plastic sweep guides that direct the cable onto the throttle drum. Identify the one that pulls the throttle off (the forward cable).
Installing the TM33: (continued) STEP 9 (continued) TM33 Right Side View TM33 Left Side View The photo below shows how the carburetor aligns vertically. Note the rear screw on the carburetor’s black top cover just hidding under the frame boss. There should also be about 1/16” clearance between this screw and the frame boss. This allows the carburetor to vibrate in its rubber mounts without metal to metal contact.
Installing the TM33: (continued) STEP 10 (continued) Left Side Cable Routing Engine Support Clutch Cable Right Side Cable Routing Cut existing cable ties as required and reroute the throttle cables through the frame so they come out on the right side of the carburetor just above the bell crank. On some bikes the clutch cable will interfere with the bell crank. If this happens remove the engine support with a 12mm socket and pull the clutch cable to the right side as shown above.
Installing the TM33: (continued) STEP 10 (continued) Using the nylon zip ties provided in the kit, cinch down the cables as required to make sure everything is tight, not rubbing and in proper position. Set the cable length adjuster to remove any slop in the throttle grip, tighten its jam nut and replace the rubber boot. Make sure throttle snaps back to idle without drag or hesitation. Check for smooth operation of the throttle and inspect the bell crank to make sure it is able to move freely.
Installing the TM33: (conclusion) STEP 12 Install the gas tank. Spray some WD40 on the two round rubber mounts that hold the front of the gas tank. Slide the gas tank back into position and reinstall the bracket that holds down the back of the tank. Push the fuel line hose onto the fuel petcock barb fitting. Position the small hose pinch clamp. Turn on the fuel and make sure no fuel leaks are present. STEP 13 Starting the bike. At this time the bike can be started.
Performance and Tuning the TM33: PERFORMANCE NOTES The TM33 pumper carburetor includes an accelerator pump mechanism and a throttle slide which is under direct control of the throttle cables. The accelerator pump squirts a small amount of fuel directly into the intake port as soon as the throttle is moved from a closed position to slightly open. Throttle positions slightly beyond open do not actuate the accelerator pump. This is a normal design for motorcycle carburetors of this type.
Performance and Tuning the TM33: (continued) TUNING THE TM33 The TM33 pumper carburetor has been jetted to work properly in 68 degrees F with a generic XT225 engine at sea level with stock exhaust. Altitude, temperature and engine conditions will play a major role in how well the TM33 performs on a specific bike. Other factors like humidity and fuel grade will also affect how the carburetor functions.
Performance and Tuning the TM33: (continued) ADJUSTING THE JET NEEDLE (continued) STEP 3 - Using a small socket remove the throttle lever bolt (58). Lift the throttle lever (58) up to draw the throttle valve (9) to its fully open position. Using a 2.5mm allen wrench (hex key) loosen the joint assembly screws (4). Remove the joint assembly (5) from the throttle valve (9). STEP 4 - With the joint assembly (5) clear remove the throttle valve (9) from the TM33.
Performance and Tuning the TM33: (continued) REPLACING THE MAIN JET (continued) STEP 3 - Place the TM33 on a clean towel. Remove the single long float bowl screw (33) and three short float bowl screws (34). Carefully remove the bowl making sure not to bend the dip tube or lose the A/P plunger (44) and spring (43). Try to avoid letting gasoline contact the float bowl O-ring (29) as this will cause it to expand making reassembly difficult.
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