Check that your carb is fully seated into crankcase. I noticed on the dynamite "Big Red" .28 engines the carb's O-ring was not sealing out the box.
Loosen the pinch bolt and push down on the carb while re-tightening the pinch bolt. If that doesn't help replace your bearing. Boca Bearings sell just the front, rear, or set. Ceramic or steel if you like.
Front Bearing Size: 7X19X6
Rear Bearing Size: 13X24X6
Links below say they are for the Mach 427, they are the same size as the Mach 2.
Steel:
http://www.bocabearings.com/main1.as...7&n=*ENK-005HP
Ceramic:
http://www.bocabearings.com/main1.as...n=*ENK-005C-LP
Ceramic High Performance:
http://www.bocabearings.com/main1.as...n=*ENK-005C-HP