This was a simple low cost way of lowering gearing for my daughters dunner LT80,  Found out the old LT80's used to be 428 pitch non O ring chain, and went to the 520 chain pitch which is way too big and heavy for the LT80, and the standard gearing for newer LT80 is 10/22 2.220 ratio, the H/J models are 12/26 with ratio 2.1666 not much lower but with less rolling resistance with the 428 chain, we noticed the quad did snap out of the corners faster, and was launching better.

Just an update on this old thread, while the older ('87 and '88) LT80's did have a 428 chain, but the 12/26 gearing is actually very slightly FASTER than the 10/22 gearing of the later models, not slower. When taking the number of teeth on a rear sprocket over the number of teeth of a front sprocket, the larger the ratio, the slower it's geared. Still, the gearing difference is so negligeable, it won't be noticed. However, using a 428 chain instead of a 520 chain is slightly noticable. If you really want a noticeable difference, get the older 428 sprockets, but use #40 farm chain. It's way cheaper and way less resistance. It's not as strong, but when you can buy 10 feet of it for $20 bucks or so, who cares. Just replace it more often.

You can also buy different sprockets for the 428 chain to gear it until your heart's content. When I'm done restoring my son's LT80 with a race engine, I'll be running a 14/26 combo with very small mx tires. I might even run a 15/26 combo if it will pull it out of the hole good. (I think it will with the small MX tires)