Wiring problem with New Riding Mower engine


Old 08-11-08, 11:49 AM
Thread Starter
Join Date: Aug 2008
Posts: 1
Wiring problem with New Riding Mower engine

To give you some background, I had a 12.5hp briggs engine fail on my riding MTD mower. I bought a replacement Briggs engine (15.5 HP) I installed the engine without any problems and have it ready to go except the wiring

Can anyone help me out on the wiring part? On the new motor, I have a wire coming from the carburator, 2 from the flywheel, and one that I believe is part of a kill switch. When I tested the wires coming from my current starter switch I have 2 positive wires (when turned on) Both red, one with a black stripe, A blue wire, and a yellow wire. I know I am asking alot here seeing that you would need Model numbers etc..just hoping I can get bits of info to help me out on this. I guess here are the questions I have so far.

What wire needs to be hook into the red wire coming of the new motor that seems to be the kill switch?

Where should I hook the 2 red wires I found that have a positve feed when the switch is turned on?

What hooks into the Carburator wire ( I assume positive)?

Any other help is appreciated.
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Old 08-11-08, 01:32 PM
Join Date: Jun 2008
Location: GA
Posts: 150
Wow!! Without the model numbers it's going to be a shot in the dark.

The owner's manual for the replacement engine should have a wiring diagram to help you identify the leads.

Two things for sure:

1. You don't want to apply power to the "kill" lead from the magneto. I know from experience that'll ruin the magneto.

2. The wire from the carburetor fuel shutoff solenoid needs to have power for the engine to run.

Now for the educated guessing:

The two wires from the flywheel are probably the positive and negative from the alternator. The positive will be used to charge the battery, and it gets connected to one of the wires from the keyswitch. The negative will be used for running the lights, and it goes to the light switch.

Beyond that, I'd just be guessing.
Old 08-11-08, 06:14 PM
Join Date: Mar 2007
Location: Southern Wisconsin
Posts: 354
The carb solnoid wire would need 12 volts applied when the switch is on and in start modes. Look at your old engine to see if you had a solnoid on the carb or not. The solnoid is there to help prevent back fire and run on when you shut the engine down. Some people remove the solnoid and put a non-solnoid carb bowl nut instead.

The two wires from behind the flywheel can be several different styles of alternators. The book with the new engine should tell which alternator that you have. A lot of the MTD's used a single 12 volt DC lead that charged the battery and the other lead was an AC feed for the head lamps.

There should be a single lead that goes to the ignition module and that would go to the ignition switch and ground to shut the engine down. You can trace it by taking the cover off the engine over the flywheel. Again the book with the new engine will show you this lead. Engine model and type numbers help with determining the wires from Briggs.

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