So is it any good to build for any other class.
The only class it may work well in is Superstock / IMOW. The 420 engine is very robust and very reliable, Being low on displacement(420cc/26ci) it cannot compete with it's big brother, the 17hp Kawasaki FC540V long stroke thumper which is allowed in IMOW & GP. You will get stomped upon coming out of the turns or on re-starts. Plus, there are no aftermarket performance parts commercially available for the 420.
Maryland Mafia Mower Racing Team (The Sod Father) President
Mason Dixon Lawn Mower Racing Association Chief Steward-2015
Mason Dixon Lawn Mower Racing Association Chief Technical Director 2016
2008 BP 1st Place Champion Delmarva LMRA
2008 2nd Place Champion Super Sportsman - Tri State LMRA
2009 Delmarva LMRA Presidents Award
2012 2nd Place Champion Super Sportsman North East National Division ARMA
2013, 2014, 2015 BP 1st Place Champion Mason Dixon LMRA
2013 GP 1st Place Champion Mason Dixon LMRA
2014, 2015 GP-T 1st Place Champion Mason Dixon LMRA
2013, 2014, 2015 IMOW 1st Place Champion Mason Dixon LMRA
2013, 2014, 2015 Presidents Award for Excellence Mason Dixon LMRA