In all of our work with the 450cc variants, people kept asking for something more affordable. So, in the process, we developed a non-stroker motor using the same 57.0 mm bore size. The motor is basically the NC450V, less the stroker crankshaft (saves approximately $3600).
We built two configurations of the 428 motor. One was to hop-up my old NC for Bob Simmons and the other as a 450cc "Production" motor (the AFM has very liberal views of what "production" means) for Mark Elrod. Both motors were based on a 57mm x 42mm engine configuration, which brings the total displacement to 428.48cc. This is where the similarities between motors stopped. See the graph at right to see how differently they ran.
Bob Simmon's motor used CP 57mm light weight, high-compression pistons (approximately 13.5:1) with a standard wrist-pin offset and Carrillo "H" Beam rods with a standard center-to-center length. The heads are milled .020" and the ports have been "optimized" on the flowbench. The carburetors are stock VFR carbs with airbox and air filter. The bike runs an RVF HRC wire harness and CDI with a "Total-Loss" charging system (there is no alternator rotor, stator or regulator/rectifier). The bike also uses Radtec Radiators to keep the extra heat rejection under control. In the graph below, note: the ONLY difference between the Red run and the Green run are the CP/G-Force 57mm pistons.
SPECIFICATIONS (428.S):
Bore x Stroke: 57.0mm x 42.0mm
Pistons: CP/G-Force Design (Std. Pin Ht.)
Rings: Yamaha FZR400 (2-Rings)
Bores: Bored Stock Cast Iron Liners
Rods: Carrillo Steel "H" Rods (Std. Length)
Crank: Balanced OEM Stock Crankshaft
Cams: Stock RVF Cams (no timing)
Max rpm: 14,500rpm
Carbs: VFR 32mm CV with airbox and air filter
Race Fuel: 91 Octane Pump Gas
Cost to build: ~$6500
Mark Elrod's motor uses the older REC 57mm pistons with a slightly lower compression ratio (approximately 12.8:1) with a 1.25mm tighter compression height (originally for the stroker motors) with Carrillo "A" Beam rods with a +1.25mm longer center-to-center length. The heads are milled .020" and the ports have been "optimized" on the flowbench. The carburetors, per the "Production" rules use the stock RVF carbs with airbox and air filter. The bike runs an RVF HRC wire harness and CDI with a full charging system (there is an alternator rotor, stator & regulator/rectifier). Due to "Production" rules, the bike also uses stock radiators which barely keep the extra heat rejection under control.
SPECIFICATIONS (428.E):
Bore x Stroke: 57.0mm x 42.0mm
Pistons: REC/G-Force Design (-1.25mm Pin Ht.)
Rings: Yamaha FZR400 (3-Rings)
Bores: Bored Stock Cast Iron Liners
Rods: Carrillo Steel "A" Rods (+1.25mm. Length)
Crank: Balanced OEM Stock Crankshaft
Cams: Stock RVF Cams (no timing)
Max rpm: 14,500rpm
Carbs: VFR 32mm CV with airbox and air filter
Race Fuel: 91 Octane Pump Gas
Cost to build: ~$6500
DEMISE: Spun Rod Bearing that led to Catastrophic Failure 
Unfortunately, Mark was a little hard on the motor and, in the heat of a race battle last weekend, he spun a bearing and put an end to this motor (see bottom of page here). Mark had won the 450cc Production race, and was on his way to 2nd in the 450cc Superbike race when the bike lost power on the last lap. He did what most riders would probably do and pinned the motor, refusing to give up on the chance for whatever points he could salvage. He managed to "Flintstone" power the bike (use his feet while still sitting on the bike) to cross the line in 6th place, after the rod bolts gave up and shot a rod through the case.
We're not 100% certain why the rod bearing spun, but we suspect a combination of crashes, the last one being exceptionally brutal, caused the oil to cavitate (get air in it) and started the bearing deterioration from there. It doesn't take long for a motor to fail after that. Having to run the stock radiators (that were in poor condition) and no oil cooler due to "production" rules did not help to keep the engine and oil temperatures down. This never helps.
