“NHRA spent countless hours speaking with the engine builders and manufacturers as well as the race teams to come up with the final engine specifications for 2013,” said Glen Gray, vice president of technical operations, NHRA. “As a result, we believe NHRA fans are in store for some exciting side-by-side racing in the Pro Stock Motorcycle category in 2013.”

“NHRA spent countless hours speaking with the engine builders and manufacturers as well as the race teams to come up with the final engine specifications for 2013,” said Glen Gray, vice president of technical operations, NHRA. “As a result, we believe NHRA fans are in store for some exciting side-by-side racing in the Pro Stock Motorcycle category in 2013.”

MAXIMUM DISPLACEMENT:

·         V-twin design  - up to 160 cid

·         In-Line 4 cylinder type – up to 107 cid

ENGINE CASE:

·         V-twin engine cylinder angle is 60 degrees.  Maximum allowable cylinder angle from vertical is 45 degrees.

ENGINE BLOCK:

·         Maximum bore spacing is 98mm for In-Line. Maximum cylinder offset on V-twin is 1”.

CYLINDER HEAD:

·         All V-twin engines must use a push-rod, rocker arm design for the valve activation. Minimum push-rod length is 8.0”.

·         All in-line 4 cylinder engines must use the overhead camshaft design.

VALVETRAIN:

o   Maximum 2 valves per cylinder for all engines.

o   The only exception is the Kawasaki engine. The Kawasaki engine is allowed maximum of 4 valves per cylinder.

·         Variable cam timing devices, pneumatic actuation and finger followers are not permitted.

FUEL SYSTEM:

·         Fuel injection permitted.

·         Direct injection (into the combustion chamber) not permitted.

·         All ECU systems must be NHRA accepted.

·         Maximum one injector per cylinder.

IGNITION SYSTEM:

·         All ignition systems must be NHRA accepted.

·         Aftermarket crank triggered, capacitive discharge (cd) ignition systems permitted.

·         Magnetos are not permitted.