Home > Engine Parts > 420cc Big Block > 420cc Big Block Performance Parts
Choose a sub category:
Shortblock Parts Cylinder Head Parts Induction and Exhaust System Parts
Ignition Starter and Cooling Parts Gaskets, Oil Seals, Gasket Sets
Sort By:
Page of 1
Main Jet Performance Upgrade Kit For GX390 and Predator 420cc Main Jet Performance Upgrade Kit For GX390 and Predator 420cc

Our main jet kit is a must for the Honda GX390, Predator 420cc engines that have had the performance K&N style air filter setup installed on the engine. Maximizes the engine for best performance and air fuel ratio.

Our Price: $8.14
Fuel Pump, Aftermarket Walbro Pulse Type Fuel Pump Fuel Pump, Aftermarket Walbro Pulse Type Fuel Pump

Aftermarket Walbro fuel pump for Clone engines, Predator 212cc engines, Ducar small block engines and many big block Honda GX390 engines.

List Price: $11.44
Our Price: $9.95
Sale Price: $8.96
Savings: $2.48
Air Filter Adapter for Mikuni 38mm Super BN Carburetor Air Filter Adapter for Mikuni 38mm Super BN Carburetor

Bullfrog Performance Products air filter adapter for Mikuni 38mm Super BN carburetor.

List Price: $38.95
Your Price $27.50
Sale Price: $19.95
Savings: $19.00
Stainless Steel Exhaust Valve 31mm Head for Honda GX390 Stainless Steel Exhaust Valve 31mm Head for Honda GX390

Bullfrog Performance Products stainless steel exhaust valve for Honda GX390 engines. The stock size exhaust valve is a 31mm head diameter in a Honda GX390. We offer cylinder head machining services to maximize head flow for better performance.
We highly recommend this valve when using high lift aftermarket racing cams to prevent valvetrain failure. Our valve will put your valve spring installed height and coil bind clearances in the proper range when using our billet valve spring retainer kit.

List Price: $25.88
Our Price: $22.50
Sale Price: $20.25
Savings: $5.63
Piston Ring Set, 90mm for Bullfrog Performance Products Forged Piston Piston Ring Set, 90mm for Bullfrog Performance Products Forged Piston

Piston ring set that fits our Bullfrog Performance Products 90mm diameter forged pistons with 1.100" compressrion height.

Our Price: $44.00
Bullfrog Pro Velocity High Performance Air Filter Kit for Honda GX390 Bullfrog Pro Velocity High Performance Air Filter Kit for Honda GX390

Our Pro Velocity high performance air filter kit fits Honda GX340, GX390, Predator 420cc and 460cc big block clone engines. Upgrade your go kart, mini bike or drift trike with our high performance air filter kit. Our kit includes the following items:


  • High flow racing style air filter 4" filter length
  • Foam Pre-Filter
  • Radiused air filter adapter
  • Choke hold bracket

Our Price: $44.95
Tachometer, Vegas Carts 0-8000 RPM Tachometer, Vegas Carts 0-8000 RPM

A great addition to any Big Block Kit or Performance Go-Kart where a sweeping analog Tachometer is desired. This Tachometer has been specifically designed for small engines with a magneto ignition such as the Predator 212cc, GX390 or 420-460cc Clone and V-Twins such as the Briggs Vanguard or Predator 670cc. Hooks up to the Kill-Wire on the ignition coil.

RPMs from 0-8000. This gauge is equipped with a Backlight.

Mounting bracket for steering column and wiring pigtail included.

85mm Diameter (3.33")

Fully Adjustable & Tunable

Excellent Alternative to the EQUUS 8068.


List Price: $57.44
Our Price: $49.95
Savings: $7.49
GX390 Big Block Bored Carburetor 23.5mm Venturi GX390 Big Block Bored Carburetor 23.5mm Venturi

Bullfrog Performance Products big block bored performance carburetor.  Our carburetor is CNC bored to obtain consistant max air flow.  Our carb has extensive carb air horn modifications along with the fuel circuits re-worked for the best transient and wide open throttle use.  Select if you need gas or methanol / alky fuel.

List Price: $171.35
Our Price: $149.00
Savings: $22.35
Forged Dome Piston Kit 90mm Bore, 1.100" Comp Height Forged Dome Piston Kit 90mm Bore, 1.100" Comp Height

Bullfrog Performance Products forged dome piston kit for the Predator 420cc engines.  This forged piston kit is a 90mm standard bore with a 1.100" compression height.  Our piston fits our 4.440" length billet rod or the ARC Racing connecting rods.

List Price: $224.25
Our Price: $195.00
Sale Price: $175.50
Savings: $48.75