pony motor grinds when trying to start big diesel motor

[JoeFarmer4]

i have a john deere 720 diesel and i just got the pup running but when i go to start the tractor i have the decompressor pulled and got to pull the other handle that moves the drive gear to the flywheel and the gears just make a horrible racket but never engage to turn the motor over but if i let the pup motor die when its almost done turning it will engage! is there some kind of adjustment for that or could the gear be sticking on the shaft the tractor has sat outside for a while

any idea is welcome
 

[wilamayb]

There are adjustments, but you'll need one of these which will cover all of the fine tuning.
720 Diesel Service Manual

 

[wilamayb]

And just as a hint, the pony pinion gear should not spin at all until the pinion has made full contact with the diesel flywheel and you pull the pony clutch lever back more to engage the pony clutch which then connects the pony pinion to the pony flywheel via the pony clutch....
 

[JIM MN]

The pony clutch disk is stuck to the pressure plate or flywheel. Take off clutch inspection cover and take something to pop it free.
 

[buickanddeere]

There is a friction plate clutch, brake, gear reduction, bearings and an over running roller "clutch". Plus some linkages.
After 55+ years of dirt, mud, manure, moisture, corrosion and wear. It"s about time to take the system apart, inspect and repair/replace as required.
 

[Rwolfejr]

If you give your choke a little tug justy before you engage the thing to bog it down a bit then shove it back right away it'll slip right in there...

Temporary way to get by...
 

[MSD]

Mine will do that once in awhile too. I found that if I don't pull the lever back to fast, just kinda ease it in till it engages that it doesn't do it.
 

[MrJDMan80]

Don't forget, that lever should be pulled SLOWLY. Pulling it fast will break the nose off the housing that holds the shaft aand gear.
 

[BushogPapa]

On my 720, I have reduced the FULL RPM by probably 25%..just to reduce wear and tear on the engine..
For Starting, I ALWAYS have the Pony warm enough that it will idle pretty well, engage the big Engine and flip to Full throttle..
Seldom, if ever grinds that way, but from Full Speed, mine will grind, too..

Hope this helps..
Ron..
 

[buck eye al]

There is a toggle in there & the lever you pull pulls on the elbow of that toggle to first slide the pinion OUT into the diesel flywheel. Once engaged, only then is it supposed move the engine side of the elbow in toward the tractor to engage the cranking engine's clutch! The return spring in there can be too weak to allow the toggle to work correctly. The shaft that the pinion slider moves on can be too greasy and gunky to allow it to easily slide first and thereby engage teh clutch BEFORE moving the gear! Have seen both.

Also the pinion and ring gear's tooth bevels can be all worn off so the leading ends of the teeth are flat & engagement can then be VERY difficult! If this is the problem, you can often "get 'round it" by trying to engage them BEFORE starting the cranking engine! With everything OFF, if you pull the lever back & it stops before it is all the way back, a tap on the cranking engine starter will roll the pinion so it engages & the lever will move back the rest of the way. With some coordination one CAN disengage the cranking engine CLUTCH but NOT disengage the pinion from the flywheel, start the cranking engine and then start the diesel. I did this for a long time on mine until I was able to replace my pinion and ring gears which were teh cause of my exact problem you describe. That was 30 years ago & I still treat these gears like gold. Back then I started the cranking engine & let it warm up then shut it off, engaged the gears, re-started it & because it was already warmed up could set right about starting the diesel.

Hope that helps a bit.

Later.