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Engine replacement for DYT 4000

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zak

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Discussion starter · #1 ·
I'm in the process of swapping out a blown 18.5 Intek motor(31p777) for an older 18hp briggs 422707. So far everything seems to be going good and lining up ok however i'm not sure of a couple things. The alternator in the 18hp had the 2 wire alternator but the blown 18.5 had just 1 wire. To make things easy i sawpped out the alt. of the older 18hp engine for the alt. out of the blown 18.5hp motor. The only thing i noticed was the magnets in the older flyhweel where a little smaller, other that that i bolted up just fine. Will i have any issues?

Does anyone see any other issues? I picked up the tractor cheap and i only did that because i had this engine just sitting there for years because the previous project never happened. I wanted to use the engine and my mom needed a tractor for her yard so it's a win, win. Thanks.
 
#2 ·
It most likely won't put out as much current with the smaller magnets.

IF you posted the tractors 917.xxxxxx number, one might be able to see exactly what the capacity of the original charging system was. Probably around 15ish Amps.

Chances are, you won't have adequate power to run headlights and electric PTO at the same time.

BTW, the blown engine should have had a voltage regulator (mounted to engine ground) between the alternator and the RED wire.
 
Discussion starter · #3 ·
9172736402 is the tractor model number. I'm not worried about headlights at all so as long as the pto will work, that's fine by me. I did try looking up some info on the alternators and the difference in the size of magnets isn't all that big. I can see a slight decrease in amperage but nothing that should make that big of a difference. I did pull the regulator off the old engine and made a bracket for it and mounted it next to the engine for easy connect/disconnect purposes.
 
#4 ·
I just did his samething. I swaped out flywheel to. I did not want to have any problems with it. I figure if its different when there is a good reason why.
 
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#5 · (Edited)
truckguy said:
I just did his samething. I swaped out flywheel to. I did not want to have any problems with it. I figure if its different when there is a good reason why.
Click to expand...
I believe you'll find the flywheels are entirely different between the OHV engine and the flat head.

The stator will most likely swap over, which saves wiring problems.

That tractor shows a 9 amp charge system.
Your "new" system will probably be enough to operate the PTO, but I don't think you'll have much extra for battery charging while doing so.

Worst case???, you might have to put it on the battery charger between mowings.
 
Discussion starter · #6 ·
Yeah, the flywheels are a different size and the starter wouldn't bolt-up so that's out. The stator fit in just fine to the older engine. I'll give it a try and see what happens, if i have to swap it out i will. Now i'm waiting on some parts so in the meantime i'll change out the hydro oil.
 
#7 ·
Yes Bill is right, you can used the pto but not much left for the battery. I guess what you could do is get one of those cheap battery tenders and wire it in with the plug easy to get to for your mom.
 
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Discussion starter · #8 ·
Do they have better alternators that i could install so this wont be an issue? Or should i install the older alternator and wire that to work? What about the voltage regulator in that case?
 
Discussion starter · #10 · (Edited)
I've been thinking about the charging system for a couple days trying to figure out what the best course of action should be to eliminate any need to constantly charge the battery. I've concluded, and please correct me if i'm wrong, that by using the 9 amp alternator off the blown engine w/the flywheel off the older 18hp engine with smaller magnets i wont be getting 9 amps, which is what the alternater is rated for w/the larger magnets in the flywheel. From what i could find, the typical pto requires 3 amps to operate. I don't know how many amps i'll be getting but the consensus is that i'll be close. So do i use the old alternator out of the engine which i assume will give me at least 9amps? That isn't a big deal since all i have to do is rig up the connectors so they work and eliminate the regulator since the older alternator has a diode which regulates the voltage, correct? So it seems to me that using the old alternator is the best solution. What do you guys think?
 
#11 ·
I would try for the most sanitary installation and see what you get.
I would think you'd still have sufficient battery charging as long as you don't-

Crank and crank... trying to start the engine and running the battery way down
&
Don't turn it off every couple minutes & restart.

Also, you get maximum charging at high engine speed, so keep it wide open when mowing.
 
Discussion starter · #12 ·
I stopped by and talked to a buddy of mine who does small engine work and other small machine repairs on the side and his opinion was it shouldn't be a problem. Boy i sure hope so. So i'm going to give it a try and just see what happens but if it was going to be an issue i'd prefer to deal with it before i button everything up. I'm getting a new battery for it with most cca's i can find and for the most part it will be strictly used for mowing so it'll be wide open while mowing without shutting it down and i'll have my mom take a lap or 2 around the yard when done w/the pto off to charge the battery afterward. So at least this issue should be done now i just need some parts to get here so i can finish up the governor and carb and get this done.
 
Discussion starter · #13 ·
I finally got the engine fired up over the weekend and she purs like a kitten. The hydro trans seemed to work fine, althought i was only able to move it back and forth in the garage since it was pouring buckets out. I still gotta replace the drive belt and deck belt but otherwise it should be good to go. And a new coil since i accidently broke off the kill wire but temperarily epoxied it back on just to get it running but i really dont trust it. Once i get everything on and working i'll see how it cuts. Hopefully no other issues. Once i get some time on the tractor i'll check voltage output and see what it is with and without pto engaged.
 
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zak
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