Engine swap

PTmowerMech

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I'm going to attempt to put a briggs V twin 21.5 hp (OHV) onto a small troybilt zeroturn, that has a single 19hp on it. The V twin, doesn't have an electric PTO. But the single does.

The first rattle out of the box, I'm having to cut holes in the surface to put the exhaust pipes. And that's not too big of a deal. But I got to thinking, what else am I about to run into? The 2 bolt patterns on the surface, measures the same. Although I'll be using different front holes.

My biggest concerns are going to be the wiring?

Plus, I just realized that I need to go measure how far the crankshafts stick out to.

Any helpful hints would be appreciated, before I get too deep.
 

BlazNT

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The biggest issue I see is you will not have enough charging to run an electric PTO. You will have to get a better stator and possible a new flywheel with more magnets. Your shaft also may not be long enough or the correct diameter.
 

PTmowerMech

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The biggest issue I see is you will not have enough charging to run an electric PTO. You will have to get a better stator and possible a new flywheel with more magnets. Your shaft also may not be long enough or the correct diameter.

I didn't think about the diameter. But I did check the length. And both were about 3 1/8th".

One thing I noticed yesterday after noon, was the choke on the zeroturn, is also the throttle cable. So, I'm gonna have to run a separate one for the choke. And get a longer throttle cable. I hope I'll have those in the bone yard.

Interesting thought about the stater. One might assume that a V twin would have more than a single.

I didn't notice a regulator on the single. That will probably have to be moved to the twin.
 

Boobala

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PTmowerMech

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Well the exhaust and muffler have become a sticker. I could've really used a schematic to drill the holes for the muffler.
 

Boobala

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Well the exhaust and muffler have become a sticker. I could've really used a schematic to drill the holes for the muffler.

I'VE got a Briggs twin, and way back, it needed a new muffler, and I thought about just "fabricating some Electrical Metallic Tubing ( E.M.T.) " to run under the mower to the back or out the sides , but figured it might be in the way for Maint. purposes, opted for my new muffler, but that's not to say it can't be done !!
 

PTmowerMech

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Got the muffler mounted (sort of). Now onto the electrical part.

I see what you're talking about with the alternator and the other wiring. It's different for sure. That one black wire that comes from under the fly wheel. The V Twin that's on it now, doesn't have that. So, the pickle starts again. The black wire that comes from under the flywheel, I'm guessing that goes through the regulator, the PTO switch and then onto the PTO.

This should be fun.
 

Boobala

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Got the muffler mounted (sort of). Now onto the electrical part.

I see what you're talking about with the alternator and the other wiring. It's different for sure. That one black wire that comes from under the fly wheel. The V Twin that's on it now, doesn't have that. So, the pickle starts again. The black wire that comes from under the flywheel, I'm guessing that goes through the regulator, the PTO switch and then onto the PTO.

This should be fun.

Here's the Briggs TWIN Engine Manual, READ through SECTION 7 .. it covers the alternator system in depth should prove helpful,

https://docs.google.com/file/d/0B6NaqjIxWV1ySkZjTTA5TGltZEE/edit

this is a wiring diagram of my 21 HP Briggs Murray 46 in deck mower tracing the wiring along with the manual should also be helpful, OR maybe leave you scratching your head..wiring a swap-job can be perplexing.

1A ELECT.PNG click to enlarge, then click once more
 

PTmowerMech

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I was gonna pull the stater off the single cyl. and use it on the 21.5. But the fly wheel is smaller, so I can only assume the stater is smaller too. But, the block has a big hole in it. Plus its cracked across the back. LOL.. Customer told me it didn't make a sound when it died.

He must've had his ear buds in listening to death metal really loud.

This is a helpful video:

He's putting 2 cyl. non-PTO engine on a mower that's wired for one. He makes things seem simple. But I suppose to him, these sort of things are simple.
 

PTmowerMech

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So without further a'do, No changing of the wires or alternator was require. When I first cranked'r up, the PTO wouldn't come on. So, I thought I had to put a more powerful alternator on it. But apparently, there's no real need for one. I mowed with it for about an hour, and everything ran great.

One question I do have, before I fry something. What's the purpose of the regulator? The engine I'm using now, didn't have one on it.
 
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