New Honda Pistons - Not Legal in 2008
From time to time, Honda Engines updates the parts used in their GX390
engine - the only powerplant used in MMRA minicup racing. For example,
in 2006 they updated the crankshaft and rod used in the engine.
Generally, these new parts are legal for use in MMRA racing - when the
change happens in the off-season.
In this case, the new piston design came after our 2008 rulebook had been
released, and our season had started. Many competitors have already
freshened their engines for the season, and they planned to run all year
before having engine work done again.
As such, MMRA will not allow the new piston to be used in competition
during the 2008 points season. Racers who buy new engines in the
middle of the season will also have to purchase an "old style" piston to put
in their engine - although they will then already have a new piston ready to
go when it becomes legal for use. This is the best way to minimize
costs for the majority of our racers, while ensuring a level playing field
for everyone. Old style pistons are still available to purchase.
The old and new pistons are pictured below. The photo shows the new
piston on the right having "shorter" rings, which are also located higher on
the piston. In addition, the new piston is engraved with "ZF6W01"
whereas the old piston is engraved with "ZF6W0".