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Champion Shaft Mounted Big Block Rocker Arm 1:1 BIG BLOCK GX340 - GX390, 420 Predators, and 13/15hp OHV, Stage 1
Shaft Mounted 1:1 Ratio Rocker Arms for GX390, 420 OHV, and 460cc
  • These are the famous "Champion" HD shaft rockers for GX390 and 420 OHV engines. They are arguably the best bang for your buck when it comes to valve train stability.
  • A shaft rocker eliminates the need for a guide plate and prevents the rocker arms from walking side to side. Further, they have considerably more rigidity than stud rockers, so they rarely need adjustment once set.
  • Studs and nuts included (Studs may require tools to install = to tight to turn by hand)
  • Fits GX390 and 420 OHV engines. Will not fit GX270s.

Basic kit for improving the performance of GX390s, 420 Predators, 13/15 hp Chinese OHVs. Simple to install, you can expect significant performance increases.

Stage 1 Kit includes

· Race/Open Air Filter & Adapter,

· Main Jet for Application (see Notes)

· Pilot Jet

· Choke Hold Down Bracket

· Choice Of Header/Exhaust

Picture for reference only and may show optional parts. See above description for actual content.

Filter should be sprayed with K&N type oil, especially in dirt applications. Oil not included

Billet Aluminum flywheel recommended. Stock flywheels, esp "Clone" are prone to failure and very DANGEROUS

Note: UT2s series Hondas (2012 & up) have Rev Limited coils and will require a new coil to exceed 4000 rpm. The UT2 coils (4 wire) can only be used with stock flywheels or 6693 ARC flywheels. If using any other Flywheels, you must run a UT1 style coil (single wire). Most 390 “clone”, 420s, and 460s have UT1 style coils already (However some Lifans and 420s have a rev-limited digital ignition)

The difference in the Kits is the main jet. We recommend you check the check your STOCK main . If stock main is a :

· #92 thru 97, use a UT1 kit,

· #98 thru #102 use a Hemi Kit’

· >102, Use a UT2 kit

Manufacturers have been know to use different jets on the same models. So it is important to know the stock jet size