How to convert a Grasshopper Commercial mower from an Opposed Twin Briggs to a Vanguard V-twin.
You must obtain the following parts to do this conversion.
1. Grasshopper part no. 503257 for Models 1620/22, 1820/22
OR
Grasshopper part no. 503258 for Model 718
(These kits will contain the following parts:
muffler and shields, engine plate and spacers, throttle assembly, coupling connector, air intake shield, shield mount adapter, and various hardware needed.)
2. Briggs Vanguard engine model 356447, type 3079-G1.
Now that you have all the necessary parts, here are the instructions.
1. Position the mount plate so that the countersunk holes are on the bottom. Place the mounting bolts from the old engine through the plate from the top down in the outward most holes that match the mounting holes in the frame. Assemble the engine to the mount plate by placing the four 5/16 X 2.5 inch bolts into the countersunk holes in the bottom of the plate, four spacers and through engine mounting holes. Install locks, flatwashers, nuts and tighten securely.
2. Assemble I-coupler to front of engine using two spacers from the old engine.
NOTE: Each bolt that goes through a flex disc must have a flat washer against each side of the disc. Position the flat washer so the smooth edge is against the disc. If the sharp edge of the flat washer is against the disc, it will cut into the disc and cause it to break apart.
3. Install electric clutch on engine. You will need to reuse the clutch spacer from the old engine, plus spacer provided with this kit. Check that the clutch does not rub against engine. Use the longer clutch bolt provided(3/8-24 X 2). Note: if hand clutch model, mount engine sheave backwards for proper belt alignment.
4. Drill two holes in seat crossmember to mount air intake shield using shield mount as a guide.
5. Place engine assembly in the frame and line up the drive coupler to the hydro drive. Tighten mount plate to frame and coupler bolts.(see note in step 2.)
6. Reconnect the choke cable, throttle cable, starter cable and fuel line and modify or replace each component as required for the particular application you are working on. Install clutch belts and check alignment.
7. Connect wires to engine. The yellow wire from the wiring harness goes to small post on left side of engine. Black(or brown on some older units) wire from the harness connects to black wire coming out of flywheel housing. This is the carburetor solenoid wire and may not be present on some older units without a solenoid on the carburetor. In this case you will need to run a wire from the light fuse in the fuse panel to the wire on the carburetor solenoid. The red wire from the starter solenoid connects to the red wire from the voltage regulator on the new engine.
NOTE: You must remove the diode in the red wire from the machine harness. The diode is located approximately 18 inches from the white plug on the end of the wire and is covered with black shrink tubing. When splicing this wire back together you may also want to add some extra length to reach the other side of the engine.
8. Install new air intake shield, using mount provided, to the seat crossmember using holes that you drilled in step four. If the shield does not clear the engine, you may have to trim off the back edge of the shield.
9. Check oil and fuel and test run the engine. Test battery voltage with the engine running to confirm that the charge system is working properly. Voltage should read 13 volts DC or higher.
10. Recheck all mounting bolts for tightness, wire connections and fuel lines for leaks.
Congratulations. You have now properly changed engines. There is a difference.