Upgrading my bearings

Run it until it fails but have a stand-by motor. Then you rebuild(if possible) the broken one. Or, if the one on the bike now runs good take the second motor and learn the things you need to know building it up. DaneilMaia has a great thread in rebuilding the 66. The right seals and bearings. When it's apart you can learn basic porting. I would not recommend using a Dremel, they spin way too fast and you can quickly over do something. Harbor Freight has a 3/8ths drill for $12.98 that spins 3000 rpm, plenty fast. There are tutorials on porting and how much to port here in the forum, easy to find and read all you can before you touch the grinder.

Tap the bolt holes and your set.

If it ain't broke don't fix it.

How long they last seems to really depend on the person. If you go easy on it, I've heard of near 15,000 miles. Some blow up under 1000. One major thing is to just do regular maintenance on it. Look for anything that seems wrong after each ride, make sure the plug is a nice color, etc.

If you're /really/ good with a dremel, and have a steady hand, I say use one. I've rebuilt plenty of blown-up Polaris Liberty motors and made them look like new with a dremel. However, in the wrong hands, they can do a lot of damage.

While the bearings in these aren't great, they do hold up for a while. Like everyone's saying, just rebuild it when it grenades.

A dremel is like any other tool, you can use it for great good or great evil.

I had a lot of luck with a dull HSS 1/4" diamter cutter, didn't eat the aluminum too quick.

But then again, I've been 'porting' paintball guns for eight years now, so take that for what it's worth.

use 20-50 percent castor in your oil mix and your engine will last a long time. i never had a problem with lower bearings but have only had one upper bearing fail-the carge disintegrated...replacing that one with a non-china made bearing -wrist pin bearing-is highly recommended.