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Simplicity 728


Bnrober2

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Hello everyone, new member and first time poster here.  I recently bought a really well maintained Simplicity 728 Broadmoor, it had a blown engine and i assumed it would be easy to find a replacement, turns out I'm struggling.  Does anyone have any advice on repowering? Id like to keep the old school look and i don't want to have to use a pull start but i'm struggling to get one that actually fits.

155778F9-290C-40B5-B22E-3A983093EBF8.jpeg

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Too keep from modifying the hood you will have to locate another 7-8 hp vertical shaft Briggs ideally with the 3" x  1" crank. When you put a different engine on it I would suggest removing that exhaust pipe as it will stress the exhaust threads in the aluminum block. 

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What exactly blew on the old engine? It may be possible to rebuild it. A repower will require you to either remove or modify (cut up) the hood and grill. They look to pretty to hack up like that. Good luck, Dave

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Im not exactly sure what blew on the old motor, but there is a hole in the side of the crankcase.  I found a "new" 9 HP briggs from a 1999 craftsman rear motor mower.  Fits like a champ, plus a gain a single HP!  Just got to get some electrical figured out.  Mine has a belt driven starter generator this one has a normal starter/magneto set up. 

9615588A-AFB7-46C3-992D-3414511136FD.jpeg

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3 hours ago, Chris727 said:

You can install the starter generator on this engine to keep it looking factory and to keep the wiring simple. 

 

That what I decided to do.  The original motor was in pretty good shape, and had been running very recently, so everything I pull off of it should work.  It's wild to me that every single screw hole matches between the two motors that are nearly 30 years apart.

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14 hours ago, Bill725 said:

THAT PIPE!

Yep except its pointed the wrong way for me! I have a pair of 1100 Goldwing chrome pipes im considering modifing to go on my Allis 716

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Okay, I might have messed something up. In the process of checking the starter generator and the wiring the regulator fell off the top of the motor and sparked now it won’t spin the starter anymore. What did I break? 

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Unfortunately it sounds like something shorted when the regulator hit the ground. I’m not familiar with what style regulator that is, but would check the wiring inside the regulator to see if anything looks amiss. Inside there are usually points that will engage due to battery power, which will send power to the starter to start and then reverse to send power back to the battery for charging. Those points have to be air gapped and are held by springs. Someone more familiar with that particular set should help you.

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Fortunately Those regulators are inexpensive to replace. To check the starter you can jump the “A” terminal with 12 volts and see if it spins. Do not put any power to the “F” terminal or it will damage the field. 

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I would disconnect the battery anytime you are removing, installing, or have a part of the electrical stuff system disconnected. Would also not hurt to remove the two wires from the A-terminal when jumping the starter. Once verified that the starter will crank and the cranking issue is resolved, then you can proceed with checking for charging operation. 

Edited by Chris727
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1 hour ago, Chris727 said:

Fortunately Those regulators are inexpensive to replace. To check the starter you can jump the “A” terminal with 12 volts and see if it spins. Do not put any power to the “F” terminal or it will damage the field. 

Crisis averted I blew a fuse and missed it in the dark last night. 

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I got everything installed and running! Question, how do I polarize the generator correctly?  The video I found on youtube says to jump a wire from the BATT to the GEN on my voltage regulator but that doesn't seem to be working, it also blows the above mentioned fuse.  Any help would be appreciated.

 

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I believe that's the correct procedure, but usually a direct jumper from the positive battery terminal is used to prevent blowing the fuse.  

3 hours ago, Bnrober2 said:

but that doesn't seem to be working

 I'm guessing you mean the S/G isn't charging the battery.  To test where the problem might be, you can follow Al's advice:

"You can check the SG unit by hooking a voltmeter to the A terminal and grounding the F terminal. the voltage chould come up to 13 to 14 volts with the engine wide open. If it goes to 15.5 or more the regulator is not connecting it to the battery as these units don't have the capability of going that high into a battery unless it is sulfatated and doesn,t take a charge. If the SG puts out OK you probably have a regulator problem."

The above is from Al's first response from this post:

https://simpletractors.com/forums/topic/570-startergenerator-gen-light-on/?tab=comments#comment-161986

He also has a second response in the above post you might want to read.   

 

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  • 1 month later...

Had 2"x3" hole in my 8hp block. Had a machinist weld a patch in. Then had it bored .030 over. Well worth the money, as they are so rare, and didn't want to make any changes to the grill. You used to be able to buy a shortblock from Small Engine Warehouse.

 

On 2/9/2021 at 7:23 PM, Bnrober2 said:

Im not exactly sure what blew on the old motor, but there is a hole in the side of the crankcase.  I found a "new" 9 HP briggs from a 1999 craftsman rear motor mower.  Fits like a champ, plus a gain a single HP!  Just got to get some electrical figured out.  Mine has a belt driven starter generator this one has a normal starter/magneto set up. 

9615588A-AFB7-46C3-992D-3414511136FD.jpeg

 

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