According to Jeff :
Are you sure the engine didn't use
Babbitt bearings
(http://www.americanbabbittinc.com/hi...t_bearings.htm) which
looks similar to aluminum?

It's exceedingly unlikely to see babbitt metal in any small equipment like
this. Small engines either have ball bearing or bearing bronze sleeves.

Their normal operating temperatures are too close to babbitt's melting point,
and it'd wear too fast at the high RPMs these motors generate.

Babbitt metal use is largely limited to _very_ large open bearings on
large and old equipment. Eg: very old and large scale machine tools like
industrial lathes of a few decades ago, large scale shafting (eg: ship
driveshafts), steam engines and the like.

You can usually tell a bearing is babbitt, because the housing is designed
so that you can pour molten babbitt into it, and sometimes even remelt the
babbitt. Babbitt bearings are cast in place and are usually quite large
beasties with oil cups etc. As the babbitt wears, you need to periodically
remelt it to reduce bearing slop.

It's cool stuff, but most people are unlikely to ever encounter it these
days, except in antique steam engines at museums and country fairs.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.