Re: Older LT50 mods
The K&N filter that I have used with good luck is the K&N RU 0200. Trinity Racing has the RU 0200 as well as the outerwears. TO install it you need to remove the stock air box completely. The easiest method concerning the mount>> you can go to a GoPed shop and get their aluminum filter mount -- for that matter you could get their K&N filter as well (smaller than the RU 0200. Remember to use red loc tite on the screws as then will be located where you can't see them on the inside of the mount surface.
One thing I found that was all important was to make sure not to remove the stock floppy rubber guard that sat over the stock filter box. It tends to keep all the dirt and water off the filter.
Now, once you go this route for air, you will need bigger jetting. I also suggest you remove the intake manifold and pull the hardened steel restrictor out. Then in the float bowl, remove the first of the two stacked pilot jets. The second pilot is actually correct for the motor without the restrictor. Finally, you will probably need to raise the needle one position and make the main jet slightly bigger.