Outdoor Power Equipment and Small Engines - yard machine lawn tractor drive belt

I have a yard machine lawn tractor. When I put the drive belt on and go in reverse the drive belt pops off. Sometimes I can go forward and back a few times and then it pops off. Really frustrating!! Also, can I use a metal starter gear or do I have to use plastic? The plastic is garbage.
Ken

Here is my usual $.01 - As for the belt, is this a new belt or an OLD belt? If new I would think you have an alignment problem or other mechanical problem, if old it sounds like its time for a new belt.

For the starter gear, how fast are you eating them up?

I had the same problem with an MTD tractor. Check the pulley on top of the tranny and see if it's loose/wobbly. Let us know.

I've never had to replace my plastic starter gears. Is this a briggs or tecumseh?

If the engine came with the plastic gear, the metal ones won't work. Or rather, they will but not long...it will chew up the ring gear on the flywheel, which is much more difficult and expensive to replace.

If you need more than one starter drive gear in 5-10 years, then you probably have a different problem causing it. I'm guessing you're not using original equipment gears, but rather an aftermarket gear.

The belt jumping off could be due to a cracked frame allowing the tranny to rock downwards, tilting the input pulley and letting the belt jump. It could be the tensioner arm out of alignment with the belt and other pulleys. Could be a loose pulley on the tranny as msidan said too.