MTD Engine Up-Size from 14.5hp to 18hp v-twin

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  #1  
Old 10-13-09, 03:18 PM
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MTD Engine Up-Size from 14.5hp to 18hp v-twin

Greetings

I have up-sized my MTD 14.5/38 engine to a 18HP V-Twin and cannot figure out the wiring.

There are 2 wire harnesses on the MTD, one harness has a "red" and a "yellow" wire, the other has a "red/black" wire and a "white wire". the only wires coming from the V-Twin are a separate "red" and a separate "black" wire.

I have tried various way's of wiring without success. Keep blowing fuses and engine will not turn.

Please help.

Thanks
 
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  #2  
Old 10-13-09, 06:37 PM
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Model number, serial number, all numbers, etc. would help.

I do not know if those down under MTDs are the same as ours or not, hopefully yes.

I will be gone a few days so I may not get to post back for a while. Good luck.

Here are some links that may help:

MTD manuals, sometimes have wiring diagrams:
PDF Manual Web Archive

Briggs and Stratton Wiring diagrams:
Operator Manuals, Illustrated Parts Lists & Wiring Diagrams - Briggs & Stratton

What is the charging voltage for my engine?

What are some common parts to my engine's electrical system?
 
  #3  
Old 10-13-09, 08:29 PM
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Hi Airman

I will post all numbers to you ASAP.

Thanks very much for your response, greatly appreciated.
 
  #4  
Old 10-14-09, 03:35 AM
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Hi Airman

Engine Details from 18HP V-Twin - Mounted to "Austwood ZTR 1500"
Model - 4227771223
Type - 0189052312
Black wire runs from engine to wire loom which run back to ignition switch. Red wire runs directly to positive side of solonoid.

Details from MTD 145/38 (no longer have engine):
Model - 13AM678F670
Type - 1H319C20182
2 Wiring Harnesses leading to engine bay. 1 has red wire + yellow wire (red leading to solonoid, yellow to safety switch), other harness has red/black wire + white wire (red/black wire leading from ignition switch, white to light switch).

I suspect the MTD Yardmachine is a dual circuit and the engine that I have transplanted onto the MTD is from a single circuit. I am unsure what to do next.

Thanks again, have a good couple of day's.

Bert from Downunder
 
  #5  
Old 10-15-09, 04:43 PM
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Model 422777
Type 1223-01
Code 89052312 (Mfg 1989)

Dual Circuit Alternator (Stator)

Red wire from alternator is 2-4 amps DC unregulated, no voltage regulator, for charging battery. To test this circuit amperage is measured not voltage. With engine running at 3600 RPM, output should be between 2 – 4 amps DC. Output will vary with battery voltage. If battery voltage is at its maximum, output will be approximately 2 amps. If no output or low output is found, test diode.

Black wire from alternator is 5 amps AC. This wire is for lighting circuit only. With engine running at 3600 RPM, output should be no less than 14 volts AC. If no output or low output is found, replace stator. You do not need this circuit if lights are not a concern.

Connector from alternator has diode encased at connector. Connector is white with two pin terminals.

I am at a bit of a wall with the tractor wiring. Maybe you can figure it out. I suggest you ignore the AC circuit (black alternator wire) until you solve the DC circuit (red wire, battery charging).

Download the parts manual for your mower and see if you can identify which electrical harness it has. There is more than one.

MTD manuals, need model and serial number: Model - 13AM678F670 Serial number - 1H319C20182
PDF Manual Web Archive

Alternator Identification http://www4.briggsandstratton.com/mi...eplacement.pdf

What is the procedure for testing the engine's electrical system?

Good luck and let us know how it comes out.

Airman
 
  #6  
Old 10-15-09, 05:20 PM
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HI Airman

Thanks very much for this info, much appreciated.

One item I negelcted to inform you that the red wire coming from the 18HP V-Twin had been disconnected for at least the last few runs on the mower without my knowlege. The odd thing is that the motor started and ran fine without it, this puzzles me some.

I will do some more investigating over the weekend and let you know how things go.

Hope you have a great weekend and thanks again.

Bert
 
  #7  
Old 10-16-09, 05:29 AM
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With the red wire disconnected, the battery is not being charged. The red wire provides electricity to the battery to keep it charged. The white connector the red wire connects to contains a diode for the DC circuit.

In your situation with the red wire not connected, the battery is not being charged. The only electrical draw from the battery is when the starter is engaged. As long as you keep charging the battery, you can continue to start the engine and use the mower without the red wire connected.

So if your mower starts and everything works. You can assume the electrical system is functioning, as it should. All safety switches are operating, as they should.

In general some safety switches do nothing more than ground out the ignition coil to prevent it from firing. Other safety switches open the electrical circuit between the ignition switch and the starter solenoid so electricity is not available to operate the starter.

Here is a good explanation of diode function I found:

"The diode controls voltage by allowing it to flow one way, from the alternator underneath flywheel to the battery, usually it is connected to the battery side of the start solenoid or through the ignition switch. The diode is necessary, because without it current would flow from battery to alternator and into ground, therefore discharging your battery when not in use."

"Very seldom does a charging system go bad on today’s engines, unless an engine has been changed from one frame to another and the wiring has been spliced and someone snips the diode out of the charging wire coming from underneath flywheel, where the alternator resides."

"One simple way to check to see if the alternator is putting out any voltage is to crank the engine up and take the positive battery cable loose, and as you try to reattach it, it should spark, or touch it to some surrounding metal free of paint, it should spark, if alternator is putting voltage to your battery."


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  #8  
Old 10-18-09, 02:25 PM
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Good Morning Airman

Thanks again for your support and info, very much appreciated.

I guess this leave me one final question. Is the black wire coming from the engine the supply wire and if so, this should be connected to the ignition switch to kill the engine when keyed off??.

Thanks again, I will try not to bother you too many more times.

Have a great day.
 
  #9  
Old 10-18-09, 06:23 PM
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What do you mean by “supply wire”? The B & S 422777-1223-01 will have an alternator with a black and red wire. Both wires should connect to a white terminal. The black wire supplies AC voltage for lighting. DO NOT connect these wires until you know what the tractor is wired for. There should be a separate black wire coming from the ignition coil. It grounds the coil when the engine switch is turned off. If you remove the engine cover you should see the wire coming from the coil.

Before you start-connecting wires read below.

Did you see the engine that was previously installed in the tractor? Was it a Briggs and Stratton, Kohler or Tecumseh? What horsepower was it? Any names on it?

The parts list shows two types of ignition switches used on the tractor you have. Pull the connector of the back of the ignition switch.

How many terminals does the switch have, five or six?

Look at the link below, is your switch like the first switch shown, part number 725-1396 with five terminals or is it like the second switch part number 725-0267 with six terminals.

MTD Electrical Parts
 
  #10  
Old 10-18-09, 07:49 PM
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Hi Airman

Thanks again for coming back to me so quickly.

The Black and Red wires coming from the engine are separate, and as you have stated, the black appears to be coming from the coil. The engine that was removed from the tractor was a B&S 14.5ph. There is only 1 black and 1 red wire coming from the 18hp B&S. The white terminal you refer to is not on the engine nor does it appear to have been on the old tractor that I pulled it from.

The black wire appears to be fine to hook up to the white wire that leads to the lighting circuit via the ignition switch (M) terminal.....is this correct and would this shut the engine down when ignition switch is turned off???

As for the red wire, I believe this a battery charging wire that needs to be connected to the red/black wire leading back to the ignition switch via the (B) terminal.

The latest problem I have found is that the stator motor gear is not contacting the engine gear and therfor not starting the motor. I read in a previous post from another page that the stator spring may be stuffed or rusty. This is possible as the engine has not been fired for about 3 months. I plan to check it and spray with WD 40 when I get home.

I will let you know how things go, have a great night.

Bert
 
  #11  
Old 10-19-09, 01:53 PM
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Hi Airman

Please disregard my last post in it's entirity, I have had a shocker.

OK, the motor that was on the MTD to begin with was a 14.5hp b&s. I did not remove the engine and therefore cannot determine what was connected to what.

After taking a closer look, I believe the black wire with a green connector coming from the stator/generator on the 18hp b&s is to be hooked up to the 6th pole on the ignition switch which is a "red/black" wire. Looking at the switching diagram, this wire is earthed out when key is turned off which should kill the motor. The red wire that appears to be coming from a separate part of the motor is the wire that I suspect is the charging wire that you confirmed in an earlier post. I believe this wire is to be connected to the red wire on the wiring harness that leads back to the solenoid via the ignition switch and is only active when turning the key to start. This will also trickle charge the battery when running. This is the way the red wire was initially set up on the old tractor.

Regarding my startor motor problem, I sprayed the starter motor spring and gear with WD40 but it made no difference. Perhaps the solenoid on this machine does not distribute enought power to the starter on the 18hp b&s. It spins fast but does not spring up and to make contact with the engine gear/flywheel. I will try connecting directly to another battery tonight to see if it fires.

Will let you know, talk soon mate and thanks again.

Bert
 
  #12  
Old 10-19-09, 07:32 PM
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If the battery is low or connected backwards the starter gear will not go up. If the bendix on the starter is damaged it may also cause the gear to remain down.
 
  #13  
Old 10-20-09, 03:29 PM
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Hi Cheese

Battery is freshly charged, so as you say, that only leaves the Bendix or the starter being connected backwards. The starter gear and spring is relatively new, so I suspect the starter is connected backwards although all seems well. Thanks for your help.
 
  #14  
Old 10-21-09, 01:56 AM
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The battery may be charged, but is it good? A charged bad battery isn't much good. How old is it, and have you load tested it?
 
  #15  
Old 10-21-09, 03:31 AM
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Hi Cheese

Battery is a few years old. I grabbed my newer battery from the old machine, hooked it straight up to the startor and the motor fired. Sounds like you are on the money as I am stummed getting my head around how the starter would be cranking in the wrong direction. The battery, soleniod and starter appear to be wired the same way as the old machine so all roads lead to a crappy battery. Will try to wire in the newer battery tomorrow night and see how she goes. Thanks again.

PS Is is possible to damage a starter by wiring directly to battery without using starter or solenoid....even if for testing puposes.

Thanks
 
  #16  
Old 10-21-09, 09:31 PM
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About the only damage would be burning of the cable post on the starter.

Just FYI, I was referring to the battery being connected backwards, not the starter. Kinda hard to connect the starter backwards with only one wire. Connecting the battery backwards will reverse the rotation of the starter (forcing the gear down instead of up)... as well as send power through other circuits backwards, potentially burning them up. Apparently that is not what your problem was.
 
  #17  
Old 10-22-09, 02:59 AM
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Hi Cheese

It would appear that I have committed the number one act of stupidity in connecting the battery up neg to pos, pos to neg...you get the picture.

All circuitry except for safety switches and engine spark appear to be ok. Have I potentially burned out the coil????

Still kicking myself for this, any advice on how to test for what else I have damaged would be great.

Chat soon mate, thanks again.

Dumbass Bert
 
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