Full Mod 27.2cc Motor 4 bolt from O'neill Brothers Racing.

After many long months of testing our full mod 27.2cc Zenoah G272RC. After having the fastest Bajas at the HPI Baja Forum's Dunetoberfest 2008 O’Neill Brothers decided that is was time to release their full mod engine line.

With the higher reliability of these new 4 bolt Zenoah motors they were able to get more hp without sacrificing reliability. O’Neill Brothers put all of the knowledge that they have picked up from years of dyno and field testing and came up with a monster.

To start they completely tore down the motor and did the following modifications:

• Machine combustion chamber for a proper squish clearance without stacking gaskets.
• Reshape piston
• Lighten the piston
• Relieve the piston to prevent seizing. 
• Modify the intake port for better flow.
• Adjust intake timing to OBR specs. 
• Resurface all ports. 
• Modify transfer ports for better flow.
• Enlarge and reshape exhaust port.
• Adjust exhaust timing to OBR specs 
• Remove stock crank and install 2mm stuffed crank.
• Install all new gaskets and c-clips when engine is assembled.