Troy-bilt horse engiine runs good , tines work,

without a proper model number it is guess work, but either the drive belt has snapped, or if the right wheel drive the left wheel, there may be a half moon key way or a shear pin. General help here, followed by parts suppliers

https://www.google.com/search?q=Troy+bilt+horse+tiller+right+wheel+turns%252C+but+left+wheel+doesn't+turn

Garden Tiller Parts - Troy-Bilt

https://www.troybilt.ca > shop-by-machine-type > garde...
Find the tiller parts, including blades, belts, tines, seals and replacement part kits, that fit your Troy-Bilt outdoor power equipment. When you need garden ...

Troy Bilt Horse Parts Lookup by Model - Jacks Small Engines

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Troy Bilt Horse Exploded View parts lookup by model. Complete exploded views of all the major manufacturers. It is EASY and FREE.
‎Horse i 7hp roto tiller (s/n 1001... · ‎8HP Electric PTO Horse Tiller · ‎2308 Horse III

Garden Tiller and Cultivator Parts ' Troy-Bilt US

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Find the tiller parts, including blades, belts, tines, seals and replacement part kits, that fit your Troy-Bilt outdoor power equipment.
Rating: 4.8 · ‎88 reviews

Troy Bilt Horse Tiller Parts

https://tb.shankslawn.com > troy-bilt-horse-tiller-parts
Troy-Bilt Horse Tiller Part Search. Search the part you're looking for by part number or model below. Troy-Bilt Part Number:.

http://www.hammerwall.com/Manuals/Troy-Bilt/Description/21A682J766/Troy-Bilt%208%20HP%20Rear%20Tine%20Tiller%208%20HP%20680%20Series%20Briggs%20and%20Stratton%20Engine%20Manual/275092/

That's the engine number. It's a 6Hp Tecumseh. Go on ebay and buy the Troy Bilt parts manuals on CD for Horse Roto Tillers (if that's what it's on). I paid $8. Definitely worth it.

Yes there will be a shear pin
It may also have an engagement cable adjustment issue

1. Remove belt guard on left side
2. Remove belt, large pulley on gearbox.
3. Remove throttle cable, idler pulley cable and shift handle.
4. Remove engine, handle, wheels, tines cover and tines.
5. Lay gearbox on side on two sawhorses, left side facing up
6. Remove all the nuts on that side. If the three shafts have corrosion, use sandpaper to remove.
7. Pry the two halves apart, then hammer the ends of the three shafts to push through their bushings. Use brass or wood to avoid blossoming the shaft ends. When shafts are through their bushings, the right side will fall away.
   

The serial number is stamped on the upper right hand side of the gear housing. It is on a flat spot just above the wheel shaft. If it is a newer model it will be on a white sticker on top of the gear housing plate. If it has the T handle it is probably an older 1980's model. If you find the six digit number I can give you the year it was made.

Frank

Some Troy Bilt Tillers were designed with a manual "free-wheel". If yours is a Tuffy (and maybe a Junior), you have to pull pins out of the wheels to move the tiller without starting it. The larger tillers, Pony's and Horses, had a lever to shift to release the wheels.

The tines are very close to the housing and sometimes you do get rocks hitting,as for the dirt it should have side panels to keep the dirt in place.

Have you adjusted the locking cam for forward. This cam is held in place with one bolt. The further you move it down the tighter it will make the belt

The problem is lack of lubrication in the pto coupling. Losen the two swing bolts carefuly,block the front under the motor. Separate the tine transmision from the housing and grease both sides with as much grease as you can work in. Work the lever as you do this. Should fix the problem.