Rewire MTD Yard Machine LT B&S 42A707

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  #1  
Old 06-11-19, 07:20 PM
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Rewire MTD Yard Machine LT B&S 42A707

After going through 2 used riders last summer I can't afford a new one. I've never been mechanically inclined so I'm working with the one I got. I've been unable to get it started this season so I decided to project it. Key wouldnt start it, so parts guy concinced me to rewire it with a push button and kill switch. In the process, I discovered A bad starter solenoid so I replaced it with a 2post and 2 terminal solenoid. That didnt start it. I've sinced replaced the carburetor and coil. I've got spark and fuel. Oil is good and new fuel lines and filter. All it does is spin the flywheel like it wants to start, but doesn't attempt to turnover. I've watched several videos and used the "Fearless Front" wiring diagram. Here's how I wired it:
1. Wire from magneto goes to one side of kill switch; other side of switch is grounded to chassis.
2. One wire from push button terminal goes to battery lead; 2nd wire from push button terminal goes to left terminal on solenoid.
3. The 2 wires from stator- The red one with the diode goes directly to the battery post on the solenoid. The white one (which I understand to be for the headlights) goes straight to the other solenoid terminal directly above the post where the positive side of the battery connects.
The thing about that white wire (headlight) that I don't get is that it has to be hooked up to the solenoid terminal in order for the starter to engage the flywheel. All the videos I watched indicated that this wire didn't need to be hooked up unless I want to run the lights. Why do I have to have this hooked to the solenoid terminal in order for the starter to work? Is this my culprit?
 
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  #2  
Old 06-11-19, 11:20 PM
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How many terminals does your solenoid have?
 
  #3  
Old 06-12-19, 04:08 AM
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The key switch has 3 positions, OFF/START/RUN. You need a wiring diagram/schematic to see what other functions the key switch performs in any position. In your case, what position is the key switch and did your modifications affect any of the functions provided by the position?
 
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Old 06-12-19, 06:10 AM
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On your switch you entered the switch with a wire from the coil/magneto and have another wire on the other side of the switch going to ground. On that circuit, across the switch, you should only have continuity to ground in the "Off" position.

In what you're doing, the grounding side of the switch (the kill wire going to ground) is a dedicated wire/circuit. The only thing on that circuit should be the coil/switch/ground. You can't route through another component to get the ground. Also you have excluded all safety devices from the machine.

That gives you the ignition circuit, spark if you have a good coil, and it should start. If it doesn't the problem is elsewhere, probably fuel, compression, etc.
 
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Old 06-12-19, 12:37 PM
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It sounds to me like you have an externally grounded solenoid and you are giving it a ground by connecting that terminal to the stator.
 
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Old 06-14-19, 05:13 PM
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Externally grounded solenoid

Thank you for your reply. Yes, it is an externally grounded solenoid (2 posts, 2 terminals). The charging wire from stator goes directly to same post that positive battery cable is hooked to. Other wire from the stator (headlights?) goes directly to terminal above the positive battery post. The thing of it is, if I dont have that wire hooked to power, then nothing happens when I push the push-button start. Im lost about this because according to my research, I don't even have to hook up the "headlight" wire. Any additional insight to this would be greatly appreciated. Thank you.
 
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Old 06-14-19, 05:27 PM
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Coil magneto/kill switch

Just so I understand what you're saying, I can't have the kill wire coming from the magneto and going directly to the kill switch terminal; and I can't have another wire connected from the other side of the kill switch terminal grounded to the steel platform?
 
  #8  
Old 06-14-19, 07:06 PM
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The way you laid out you had it wired is good. Post on the coil/magneto to switch. Then from the other side of the switch to frame ground. Continuity to ground only in the key "Off" position. The kill for the ignition is grounding the magneto (Off position)

Then keep in mind things like the seat switch or PTO safety switches have been bypassed.

Are you using a two terminal switch for the kill or a multi function switch with a key that controls more things? If it's just a "Flip" switch it will either be in the Off (kill and grounded) or the On (run).

The stator wires you're discussing are a different subject..
 

Last edited by marbobj; 06-14-19 at 07:25 PM.
  #9  
Old 06-14-19, 07:22 PM
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To make the solenoid engage, you need to put power to one of the small terminals, and ground the other. The headlight portion of the stator has nothing to do with it other than it's a path to ground. The solenoid is using it as a path to ground since it's not wired directly to ground. Make a connection that jumps one terminal to ground and leave the headlight wire disconnected.
 
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Old 06-15-19, 06:31 AM
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Because you have not answered my earlier question about the key switch, I can't help you any further. Did your "research" involve viewing the wiring diagram and/or schematic? Also, defeating safety features is something I do not recommend.
 
  #11  
Old 06-15-19, 05:38 PM
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To Marbobj

It's just an on/off switch with 2 terminals. I've tried starting it in both positions when it wouldnt turn over at the first attempt
 
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Old 06-15-19, 05:43 PM
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I put a push button start (with 2 terminals) on it. I bought it used last summer with all the safety switches bypassed except the brake/clutch. I by passed that one when I put the push button start and kill switch on.
 
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Old 06-15-19, 06:19 PM
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With that switch in the on position (no continuity to ground) ;you should have spark at the spark plug and it should start with fuel, compression, etc., unless you have a fuel solenoid on the carburetor.

If so you'll need a multi function ignition switch to provide a "Run" function. From there you could send current to the fuel solenoid on the carburetor.
 
  #14  
Old 06-15-19, 06:52 PM
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I dont have a carb solenoid. It gets spark. Im trying to figure out how to upload a picture that I took, but keeps telling me I need a url. How do I upload a photo
 
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Old 06-15-19, 07:05 PM
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I dont think this site will allow me to upload a photo using my phone. I can do it from a computer
 
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Old 06-15-19, 07:34 PM
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J don't have a carb solenoid. It gets spark
Then you're good on the ignition.

If the starter you have will spin the engine over, it should start, given the engine is in decent shape with compression and the carb is providing fuel like it should.

There is nothing in your posts that would indicate why it doesn't. This is as far as your wiring is concerned.

You might try taking the plug out and spinning the engine over half a dozen times, then drop a spoon full of fuel down the plug hole. Then stick the plug back in it and see if it will try to start.
 
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Old 06-16-19, 07:48 AM
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That sounds like a plan and will give it a whirl after I submit a picture
 
  #18  
Old 06-16-19, 08:18 AM
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Please see photo. I labeled what I've done. Remember that I have spark (gapped at .030) and good compression. Now that I unplugged that white wire (headlights), Nothing happens. Only when that white wire was hooked to the right solenoid terminal did it crank. Black battery wire is attached to left side of solenoid mount screw on the back side. Positive is connected to rt post of solenoid.

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Last edited by PJmax; 06-16-19 at 09:16 AM. Reason: resized picture
  #19  
Old 06-16-19, 09:17 AM
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Connect a wire from the right solenoid terminal to the green ground wire that goes to a bolt.
 
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Old 06-16-19, 01:13 PM
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I answered this in post #9 already, but it's like I never said anything. ???
 

Last edited by cheese; 06-16-19 at 02:13 PM.
  #21  
Old 06-16-19, 05:45 PM
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Ok, am looking forward to a break in the weather to do this. Thanks for hangin in there with me, this stuff can be like Greek to me and my own wires between my ears oft get crossed. Im enjoying the learning experience, thank you. I used to throw money at these problems.
 
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Old 06-16-19, 11:10 PM
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No problem, let us know how it goes!
 
  #23  
Old 06-17-19, 06:43 PM
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I made a connection from rt terminal to green wire. Nothing. I rechecked spark and was good. While I had plugs out, i checked compression. That was good. So i put a half dropper full of gas into each hole. Nothing. Just keeps cranking.
 
  #24  
Old 06-18-19, 04:57 AM
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Hi, I don’t get the push button arrangement, if you have the correct ignition switch this Dia. should work.
Geo
Sorry it’s not to clear, I’ll try something else

http://www4.briggsandstratton.com/mi...0Reference.pdf
Page 125 or 126
 
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Last edited by Geochurchi; 06-18-19 at 05:12 AM.
  #25  
Old 06-18-19, 12:45 PM
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Okay, so we had two problems and now one is corrected right? The solenoid is working right now? Here's what I was addressing:
{{{"The thing about that white wire (headlight) that I don't get is that it has to be hooked up to the solenoid terminal in order for the starter to engage the flywheel."}}}.

Now the starter does work, but the engine won't run, correct? Have you tried with the kill wire disconnected from the coil to see if it has spark?
 
  #26  
Old 06-18-19, 06:57 PM
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The solenoid is working because the push button engages the starter, which in turn activates the flywheel. Flywheel just keeps spinning but it doesn't want to even attempt to turnover. I did recheck the 2 spark plugs. Nice blue spark gapped at .030. I even checked compression. I got a nice, startling puff when I put my thumb over the holes.
 
  #27  
Old 06-18-19, 08:45 PM
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So if it;s turning over and you're getting spark, then you probably have a fuel issue keeping it from running. Is there fuel in the carb bowl?
 
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Old 06-19-19, 03:42 AM
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Have you tried to put a T spoon of gas into the cylinders to see if it will fire up?
Geo
 
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Old 06-19-19, 05:58 PM
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I do see fuel dripping out of the injector and I have tried putting gas directly into the cylinders. Could it be a timing issue?
 
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Old 06-19-19, 06:27 PM
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There is no injector. I'm not sure where you have fuel dripping from, but it may be flooded if fuel is dripping.
 
  #31  
Old 06-24-19, 10:55 AM
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It was flooded. Neighbor came over, pulled the plugs, lit both holes with a lighter (that floored me) and started up. However when he tried starting it again, the flywheel chewed up the teeth on starter gear. Scored another gear, same. Pulled starter and shaft had some wiggle and there was no spring. Starter gear wasn't falling. New starter arrives today. We shall see.
 
  #32  
Old 06-26-19, 07:52 PM
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Got er going. Burned off flooded fuel and a new starter did the trick. Thank you for the help. I learned a lot.
 
  #33  
Old 06-27-19, 12:52 AM
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Glad you got it fixed and thanks for the update! It's great when you can get something going on your own!
 
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