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aw shucks...i bought a 720

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5020s rock

12-13-2007 01:29:55

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hi-- i bought a 720 D. i need to clean the injectors and find a wiring harness and convert the starter(electric start) from 24v to 12v.
suggestions from the previous owner. can a starter
be "converted", if so whats a fair cost? who do you guys recommend for a wiring harness? it has an
alternator,so i am aiming for a whole 12v system.
any help here is appreciated. thanks

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gpuller

12-14-2007 06:24:23

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

I converted my 720 to 12V, if you need any info drop me an email.

Send the pumps and injectors to Garry Power in Tx.

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5020s rock

12-13-2007 23:21:27

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

hi--thanks everyone !! i guess i dont need to convert the starter. it must be i got a "tweener"
it has an alternator but a 24v starter????
i should get the tractor soon....then ill be back here. the replies were great, all over the place...somthin about a 720 makes us all remember..different things....a different time...
see, i am getting sentimental-lol no,input on the injectors?? c'mon!! bye

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BLinWMi

12-13-2007 17:04:47

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

I am no electrician, but I don't understand why anyone would need to stay with 24 volt to get the 720/730s started. How is it a monster 5020 with a 531 can start ok with a 12 volt system, or heck for that matter, a 4960, but no one ever has any luck getting the 2 cyl diesels to start? I have not had any experience cuz mine is pony start, but don't get it.

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mjbrown

12-14-2007 03:53:41

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Re: aw shucks...i bought a 720 in reply to BLinWMi, 12-13-2007 17:04:47

I think the reason they are hard to start on 12V has to do with the fact that each compression stroke on the two cylinder is compressing 1/2 the 400 ci displacement of the engine . The 531 is a six cylinder so each compression stroke is 1/6 of swept volume.

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GeorgiaHayFarmer

12-14-2007 04:15:01

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Re: aw shucks...i bought a 720 in reply to mjbrown, 12-14-2007 03:53:41

You read my mind on this reply. I was thinking the same thing. I wonder what the difference in compression ratio is between the two.

Scott

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wilamayb

12-14-2007 07:10:41

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Re: aw shucks...i bought a 720 in reply to GeorgiaHayFarmer, 12-14-2007 04:15:01

It's not the ratio that is the problem. They will both be pretty close to 16:1 . It is the volume per cylinder that we have to consider. It takes a lot more power to compress a 6" bore cylinder 16 times less it's size than it does for a 4" bore.

The problem is the starters that are available that will bolt up with the correct number of pinion teeth do not have enough torque to roll the engine on 12V.

Here is my theory: If someone could retrofit a gear reduction starter off of a 12.5, 13.5 liter or a 9.0 liter I feel certain tha it would whirl it over to start even in the coldest of conditions. My only fear is that we would have to strap on an extra batteries to get enough CCA's to make the said starter effective. Having to put the batteries under the seat puts a real crunch on things. The ES seat box helps, but even when installing the large 12V batteries in my 730D ES I had to remove the float ride to get them into the box.

All in all there is no way to make the tractor have a factory appearance and run the starter motor on 12V unless you are willing to sacrifice cold weather starts.

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pjcarlson

12-13-2007 15:22:34

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

Just curious. Why do you "need" to convert it to 12v

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RobMD

12-13-2007 10:05:51

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

Repair the existing 24volt system. Don't get yourself into a big bundle of doo-doo. Call jim at agri-services to get his new wiring harness and 24v relay system.

AGRISERVICES

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Freddy

12-13-2007 08:09:09

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

I must say I love my pony motor. But then I have a good one. Always starts no matter how cold it's outside. If only the gas tank was larger for the pony I wouldn't keep running it out of fuel..LOL..

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John T

12-13-2007 07:38:20

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

5020 I know you dont wanna hear this lol, but I bet she would start better if you bit the bullet and paid the bucks to have the 24 volt system repaired instead??? Still its your tractor n your choice so go for it n best wishes. When I had a 730 elec start diesel I kept the biggest highest rated heaviest honkin batterys available n had all good clean heavy cables n she started UNLESS it was like extermely colddddd dd. When we farmed with it and my 720 pony start the elec start was driven by the "First Wife" Old Julie. Oh those were the daysssss sss we didnt have nuttin but didnt know the difference or care lol and even had fun n made money farmin then in the sevetnies when corn was $3.00 but far less overhead n input costs as compared to today grrrrr rr

John T

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mjbrown

12-13-2007 04:36:09

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Re: aw shucks...i bought a 720 in reply to 5020s rock, 12-13-2007 01:29:55

This subject comes up once in a while. I tried to convert my 730D to 12V and never had satisfactory results after spending $800 or so.
I had the starter windings changed to 12v and used two large batteries and huge cables and it wouldn't spin the engine fast enough decompressed to kick it over on full compression. I tried two 8V batteries in series for 16V at the starter and it would work in summer but no go in fall, winter or spring. I am now back at 24V and it starts great. Feel free to repeat the experiments if you must.

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Mike M

12-13-2007 06:26:54

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Re: aw shucks...i bought a 720 in reply to mjbrown, 12-13-2007 04:36:09

I had that same experience when I changed a old JD500 TLB over to 12V.

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