“Oil in frame” design with no oil tank.

Yep, oil is routed inside the frame tubes with no oil tank. 1) 2)

Engine:

• Inexpensive Pressure-Relief Mod Install this mod at your own risk! It is purported to minimize wet sumping caused by sustained high RPM operation of modified Evolution Engines.
  See more on this discussion here which originally began with an issue regarding 04 and up oil usage: http://xlforum.net/forums/showthread.php?p=754838#post754838
• Custom Oil Pump Hoses
• Installing the Ultimate Crankcase Vent

Primary:

• Homemade Primary Oil Sight Gauge