Rear Pulley Swap on a MTD

I was wondering if anyone had any experience with swapping out the rear pulley on one of the mtd shift on the go mowers, i dont really want to touch the front pulley since i have just bought a belt for it and i was only looking for it to go no faster than 25mph/40kph. its probably going to stay mostly stock in the drive-train and wheels department and will be used only for trail riding and not mud. one my main concerns it the pulley being splied and if there is a specif size i need, any ideas?

The pulley is splined like you said, which would present a problem. Another problem would be figuring out the rear belt size to accommodate the new smaller pulley. Also the vari-drive linkage will have to be re-adjusted as well, but once you get used to it its not too hard to do that. I've done it on my MTD quite a few times. It should be possible for you to do it, it just might be a bit of work.

AllisKidD21 what size pulley did you put on?

Well my MTD still uses the original pulley as it's not really a speed machine, but I swapped in a completely different transaxle all together. I made an adapter so I could still use the splined pulley on the keyed input shaft of the new trans.