720 diesel

[60jds]

ok guys got the tractor out and ran it pulled a 4020 up the road in 5th gear up hill to get the 720 hot to help free up the rings. let the tractor warm up by driving it around and then went out and done tug a war with the 4020 went back pulled the tractor in the shop pulled the dipstick out of the pony and oil can running out of it big time is there a reason that there is diesel oil coming out of the pony. Thanks For the Help David

 

[Bob Harvey]

Pretty sure it is a 'Bad' reason. I know nothing about your tractor, but it don't sound good. Other 'Pros' will know. b

 

[60jds]

yeah im hoping its not a bad reason really looking forwards to pulling a little bit with it this spring.

 

[Freddy]

the pony breather is also the big engine breather. If the rings are stuck or not so good blowby can be feed into the small engine. wetstack might also be occuring.

 

[FactoryFarmer]

Way to much crankcase pressure which can be cause by stuck rings, a couple of cracked rings, or a cracked piston. Either way, the engine needs to come apart.

 

[kendak]

be sure you got real DEEP pockets before you turn a wrench on a 2cyl. diesel

 

[Cowguy74]

Check under the valve cover an under the pump cover and see if the fuel lines are leaking. That's the easiest place for it to get into the oil.

 

[Mike M]

Sure hope you put 4020 in tow position or you will have another tractor project. Maybe if the engine was running it won't kill the tranny?

 

[60jds]

there is no fuel in the oil that i can tell ive had that problem before on 4020s. there is no broke rings in it cause it aint making no weird noises. Im thinkin the rings are stuck and need to get broke loose and reseated im going to hook a disk and go hit a field tomorrow after work it will either go or blow is how im looking at it.

 

[60jds]

yeah it was in tow and engine was running know all too well what can happen if you dont put them into tow.

 

[FactoryFarmer]

(quoted from post at 18:43:56 03/06/12) be sure you got real DEEP pockets before you turn a wrench on a 2cyl. diesel

That's what everyone says but it's not the case at all...

 

[skip33652]

broken rings won't make any noise except whoosh-as the air goes past. the the black dash tractors and all jd replacement pistons had keystone rings( triangle shaped) which are super but-- when the ring gap gets excessive they end up with a lot of side clearance and flutter which causes them to break. Put a pipe coupler and a long piece of pipe on fill tube and go out and run it and watch how much blowby it has.

Just because you are looking for an easy solution does not mean there is one.

I would bet a lot of money you have at least one broken ring.Paul

 

[ET]

A friend of mine has a 730 that does the same thing. Filled the pony to over flowing with oil from the main engine.

 

[Kent Petersen]

you may a well plan on reboer and new pistons just for a starting point

 

[Anonymous-0]

Seems as though worn/broken/stuck rings allowing lots of blowby would lower the compression enough to make it hard to start. Redo the test you did pulling the 4020 with the oil fill cap loose or well vented to give blowby another place to escape. If there is a lot you should see it. If the pony still gains oil you have another problem. If you are leaking fuel into the oil the main engine dipstick hole will spew a fountain of oil when removed.

 

[60jds]

went out and disked with it for about an hour well needless to say its getting parked until this winter for a engine redo and a pony delete going to make it an electric start. Anybody know what a pony is worth that runs but needs resealed and carb rebuild.

 

[Scott 730]

(quoted from post at 17:11:27 03/07/12) a pony delete going to make it an electric start. quote]


:roll: :roll: :shock: :shock:


Good luck

 

[buickanddeere]

Unless you want to spent a pot load of cash. Just make certain the coolant temp is up to 195F. Pull the injectors and make certain they are breaking at the proper pressure with good pattern. Use a straight weight 50 or 60 motor oil. Make certain the PCV port is wide open. Put up with the goober and slobber.

 

[FactoryFarmer]

(quoted from post at 18:41:18 03/07/12) Unless you want to spent a pot load of cash. Just make certain the coolant temp is up to 195F. Pull the injectors and make certain they are breaking at the proper pressure with good pattern. Use a straight weight 50 or 60 motor oil. Make certain the PCV port is wide open. Put up with the goober and slobber.

What does everyone say diesels are so expensive to rebuild???

Let me lay it out, both tractors were completely redone but these lists are just everything to do with the engine.

Here is the last one I did (720):

Complete gasket kit (from Deere): $180

Bore block .125 over, magna-flux, bead blast, baked etc: $250

Grind valves, neat seats, beadblast head, resurface, etc: $150

True up bearing surfaces on rods: $25

Calibrate/rebuild fuel pumps, clean injectors: $325

New pistons, pins, rings: it was either $550, can't remember

Rod bearings: $175

Total Cost: $1655


Now here is my 37 A (bought new and never left the farm!) :

gasket kit from Deere: $280

Misc gaskets that weren't included: $150

beadblast, bake, magna-flux, hone block: $250

beadblast, bake head, new valves, resurfaced, etc. : $280

new shims for rods: $300 (yeah, really!) :roll:

rings (it's a funny set because the tractor had odd JD gas pistons): $80 or so

rebuild carb: $250 (didn't do it myself)

Rebuild mag: $350 (didn't do it myself)

Total cost: $1940


Unless it's a super special tractor like the A I'll take the diesel any day of the week because you really have something when your done!

 

[Anonymous-0]

You rebuilt carb and mag how about the cost of rebuilding the
pump and injectors to make the diesel as "new" as the A.
Guessing you wouldn't do those yourself either. Now watch the
cost climb.

 

[FactoryFarmer]

(quoted from post at 20:42:22 03/07/12) You rebuilt carb and mag how about the cost of rebuilding the
pump and injectors to make the diesel as "new" as the A.
Guessing you wouldn't do those yourself either. Now watch the
cost climb.

Look at item #5 on the list, plain as day. I didn't do them myself either.

 

[60jds]

did they know wat a pcv valve was back then? say i had it up to around 200 most the time i was out there i was working the crap out of it pulling a 10ft RWA disk in 4th gear wide open it was working it the whole time.

 

[60jds]

yeah im in the process of overhauling a 60 now so far im thinking i have almost 1100 in it so far and thats not counting the new main bearings and machine shop bill and the price of the bearings. Im thinking on the 720 is the cost of converting it to electric start.

 

[60jds]

yeah im thinking that there is a ring also broke. when i get my 60 running and new clutch in the 3010 and also in a 4020 that we still farm with im going to pull it apart and start looking.

 

[buickanddeere]

It's not a rebuild unless the cam and followers are reground .
More often than not the diesels have ruined flywheel splines.
Often idler gear and bearing problems too.

 

[FactoryFarmer]

(quoted from post at 15:33:12 03/08/12) It's not a rebuild unless the cam and followers are reground .
More often than not the diesels have ruined flywheel splines.
Often idler gear and bearing problems too.

I took mine out to check them over but I didn't really know who to trust them with. They looked fine anyway so I put them back in.

Mostly 70's had flywheel problems because of the lack of decompression on shutdown. From what I have found on the 720's and 730's loose flywheels come from not decompressing on shutdown or someone didn't get it tight the last time they took it off.

 

[buickanddeere]

The wee rocking a flywheel takes during shutdown
is insignificant to the dynamic forces during
operation an low rpm lugging in particular.
If every time a flywheel was removed new bolts and
a torque wrench were used. Worn splines would be
unheard of.

 

[buickanddeere]

Why ruin the tractor with an electric start conversion? Not a cheap swap if done properly. A pair of new group 31 batteries every 3-5 years add up in $ too. In the Delco line, there are only 3 different models to even consider with anywhere near enough power.