Wire diagram for most B&S engines

This wire diagram will work for a big majority of Lawn Tractors with a B&S engine.
This is the wire set up i got in my tractor and i like it.
https://www.atltf.com/t1968-racing-lawn-tractor-mean-rabbit



PS: If you use the teather switch when you are done, un hook the teather switch. If you don't it will drain your battery.

This will actually work for just about any tractor. I was thinking of making one for the forums use but you beat me to it.

Ddwannabe wrote:

This wire diagram will work for a big majority of Lawn Tractors with a B&S engine.
This is the wire set up i got in my tractor and i like it.
https://www.atltf.com/t1968-racing-lawn-tractor-mean-rabbit

PS: If you use the teather switch when you are done, un hook the teather switch. If you don't it will drain your battery.

This will be helpfull when i rewire my mud mower.

There is a problem I am seeing here. You have your lights' power source, ammeter feed, and carb kill power source attached to the starter side of the solenoid. If you wired it exactly as you have it posted, these parts will only work while you are cranking, and the engine will die as soon as you let off (carb kill).

I think you need an ignition switch to connect all of these to.

o dang i just noticed that sorry ill fix it.

fixed

Thanks, this is way nice and now it's even correct.

i just rewired my mtd and i used this thank you for posting it simplified a lot

yea I cut out a lot of spaghetti of the safty switched it and only had to run a wire from the key ignition to the solinoid.

I am having a couple problems with the diagram even though I have a Briggs & Stratton engine. First of all my mower has a 4 pole solenoid, not a 3 pole. Secondly, I have two wires coming from my starter mower, not one. So I am wondering how the diagram should look to suit my mower? I hope someone can help.

DIYfreak wrote:

I am having a couple problems with the diagram even though I have a Briggs & Stratton engine. First of all my mower has a 4 pole solenoid, not a 3 pole. Secondly, I have two wires coming from my starter mower, not one. So I am wondering how the diagram should look to suit my mower? I hope someone can help.

On the 4 pole solenoid, one of the blade tangs goes to ground and the other is the lead from the key.

On 2 wire charging units, one of the wires should have a lump in the wire near the plug. Its a diode, and that lead goes to the battery positive because its the charging wire. Usually its red.

The other wire without the diode lump is used to go to lighting. However since it is entirely dependent on engine RPM most people dont use it since the lights will flicker.

Thanks for the speedy reply Doug. I'm finding it a bit confusing. My mower is a Stiga 63 brand. It appears to have two black wires coming up from the starter motor. There is a separate wire coming from the Alternator, also black. I cannot see any lump for a diode.

Can you take a pic?

Doug wrote:

Can you take a pic?

I figured it out. There are two black wires coming from my starter motor. One is + (Pos.), the other _ (Earth). They only change to the red and black wires at a connection, so it was easy to tell which was which. I could not find any diode on the alternator wire.

I have now re-wired the Stiga mower as per the diagram and the additional advice. It has full crank now and starts straight away. Before I was always struggling with very sluggish cranking, no cranking at all, and/or a flat battery. There must have been a bad connection somewhere in the old circuitry, but I could never trace it. By completely bypassing the safety switches and the electric card, the problem is solved.

Many thanks for your help.

Glad you got it sorted!

Greetings,

I just found this forum and used the corrected diagram to rewire my JD D125 to eliminate all the safety switch nonsense, it has a 20HP Briggs V-twin. I followed the diagram (i left out the light switch, not needed) and for the carb kill I left out a switch (ran a straight wire to the positive side of solenoid) since I am not racing with it (mowing only), however I cannot get the starter to kick over at all now, the solenoid works fine. Any suggestions on what I may have done wrong? Thank you for listening.

Greetings everyone,

I figured out my starter wasn't properly grounding to the engine block for some reason, so I wired in a new ground and got it to spin over, however, it did not crank. I am thinking the fuel shutoff solenoid isn't working and will bypass it tomorrow if I can figure that out. I will update y'all on the progress.

Howdy guys,

I grounded the starter, got plenty of spin, no crank. I tinkered all day sunday to no avail, I then went back to my old friend Google, searched for possible solutions and found a youtube video on how to test the coils/magnetos and I found out that over the past few months since I last ran her the coils/magnetos have degraded beyond being able to create enough spark to ignite fuel. Supposed to be 2.5k-5k ohms resistance optimal, I had 7k on both of them so I was getting spark just not anywhere near enough to go vroom. I have ordered replacements since I am an honest man and won't steal them off my neighbors mower, LOL!

This forum is a wonder of small engine awesomeness and I am glad to be here!

Exellent idea to simplify the wiring, something I'm doing on my current build. Is there an electrical genius out there who could show how to combine the simplified wiring diagram shown above with the MTD ignition switch (what goes where?).

Unfortunately there are several variations of (MTD) tractors and therefore key switches throughout the years,  older ones being really basic and newer ones having "kill relays" and "control modules" for the saftey interlocks to contend with so there's not going to be a cut and dry approach here... with that being said I'd be happy to help! Lol.

There are also different types of charging systems throughout the years so thats another consideration on its own. I have plenty of experience rewiring and engine swapping so I've probably already seen the worst of it all!

First off, do you have a multimeter and know how to use it? Or even a light probe?

Is the engine original to the tractor? If not please post the full model number of the engine and the tractor (regardless) so I can locate wiring diagrams to see what we're up against.

Are you trying to solve an existing problem (saftey interlock woes? No start with key?), doing a engine swap or just trying to remove unnecessary wiring?

***Edit*** Are you working on that yellow Dakota?

Thanks for the prompt reply Brianator! Yes, it's the yellow Dakota. It had suffered from someone mucking about with the wiring (sticky tape and twisted together joints) and I think that was why it had been abandoned in a barn for years. I found it on a local ad and was just going to use it as a spares supply, but on investigating it, it was far to good for that. I presume the engine (10hp B&S) is original but the blower housing was missing and no obvious numbers.
Anyway, I'd like to use the key start if possible for no other reason than it's there and I don't want to drill more holes in the thing than are there at the moment! Yes, I do have a multimeter and a light probe. Simplicity with no safe cutouts is what I'm after.

Okay well this won't be TOO bad then, we may have to go step by step however. Here's a wiring diagram for my very similar mid 1980's MTD. I hope you're able to see it decently I had to screenshot and crop the photo from the manual.


Best thing to do is start by mapping out the switch with your multimeter and writing down wire colors/post letters that SHOULD be stamped on the fiberboard on the back of the switch, hopefully the colors on the diagram match your tractor but either way we'll figure it out. I apologize I can't use my tractor as a reference, I removed the whole harness and started from scratch.

Probe through the back on the connector on the key switch while the battery is hooked up for this next part: When the key is in the OFF position that terminal should have continuity to ground which is KILL and no continuity when switched to ON/RUN. The ON/RUN position should show 12v when switched and START will show 12v when engaged only.

Then start pulling all the saftey interlock wiring forward so you can hang it out the side of the dash (you can leave the actual switches in place if you choose) starting at the back of the tractor and working your way forward, now you have to start trimming wires....  if you notice the wiring for switch # 9 runs from the alternator to the key switch, that's the charge wire. Cut that wire off at the # 9 switch (as followed from the engine) then extend it to either the battery terminal on the starter solenoid (thick red wire labeled # 2) or to the positive post of the battery itself, now you have a simplified charge circuit. From the other side of switch # 9 cut the wire off the key switch leaving enough to attach another wire to if needed.

I'm going to leave it at that for the moment and wait for you then we'll move to the next step.

If you wouldn't mind, please start an actual build thread for the tractor. It doesn't have to be fancy but at least a brief explanation and a few pictures of the machine excluding any of what we're talking about now. I'll be able to move this info over to it and you'll have a full, complete and organized record of your machine to be able to use as reference in the future!

Thank you so much for posting this, (10 years later lol)!! I have used this diagram to rewire my cub cadet 1225 with a Briggs engine, (with the addition of wiring for the electric PTO) and it works just fine. Made it sooo much easier than having to utilize the old wiring diagram. Starts and runs reliable now. Thanks again.