Cyber Sale
Cyber Sale

Speed Kit; GX340 to GX390, 420 Predator, & 13/15hp OHV; Stage 2

  • $150.00
  • $192.00

Speed Kit Selection Guide

Stage 2 Hop Up Kit for GX340-GX390, 420 Predator, and 13/15hp (440-460cc) OHV Engines


As a step up from the Stage 1, this kit is designed to improve the power and durability of GX340s and GX390s.

Includes:

  • Race/Open Air Filter & Adapter
  • 23.5mm (Bored) Honda Race Carb
  • Heavy Duty Valve Springs
  • Offset Timing Key
  • Twister Camshaft
  • Carb and Side Cover (7-Bolt) Gaskets
  • Additional main jet for optional tuning
  • Optional Header/Exhaust
  • Optional Aluminum Flywheel


*Note: Use of the choke bracket requires use of a stock Honda (or Chines OHV) "Air Filter-to-Carb" gasket. This is not included in the kit. You can use the one that came with the motor.

UT2 series Hondas (2012 & up) or later have a built-in rev limiter in the coil and will require a new coil to exceed 4000rpm. The UT2 coils (4 wire) can only be used with stock flywheels, and 6693 Billet flywheel.

If using another billet flywheel, you must run a UT1 style coil (single wire).

13/15 Chinese Engines (414, 420, 460) usually have UT1 style coils already. However, some Lifans and 420s have a digital ignition and will need a Honda UT1 coil to run the billet flywheel.

Header not included unless specified.

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

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

Warning: Billet aluminum flywheel recommended. Stock flywheels, especially "clones" are prone to failure and are very dangerous!
FAQ Accordion with Animation

Frequently Asked Questions

When will my order be shipped and how long does delivery take?
Orders containing in-stock items typically ship within 3–5 business days. Orders that include assembly will require 7–10 business days to prepare. Please note that during the holiday season (Thanksgiving through Christmas), processing times may be longer due to high order volume. Once your order has shipped, you’ll receive an email with tracking information. Most orders are shipped via Less Than Truckload (LTL) freight and generally arrive within 3–7 business days. Deliveries to remote areas (such as mountains, forests, valleys, or islands) may take longer. You can check the estimated delivery date on the carrier’s website using the tracking number we provide.
How your vehicle is shipped?
Unless otherwise noted, the vehicles we offer are shipped crated or on a pallet and do not come assembled unless you’ve selected our assembly service. Assembly typically requires a few basic tools and mechanical knowledge. If you're not confident in your ability to safely assemble a high-speed off-road vehicle, we strongly recommend selecting professional assembly or having it assembled by a local mechanic.

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Do you offer financing?
Yes. Buy-now-pay-later financing is available with our preferred partner, BreadPay® (please see their icon under product pricing for details).

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How can I get assistance if I have question on products?
Please call 888-886-5846 and talk to one of our knowledgeable sales representatives between 9am-3pm PST. Or send us email at orders@gokartsusa.biz.
What warranty is included with my purchase?
You're covered with confidence at GoKarts USA®. Your satisfaction is our top priority. Every purchase comes with manufacturer-backed warranty protection—including up to 12 months of engine coverage—to keep your ride running strong. TrailMaster products also include a 6-month parts warranty for added peace of mind.

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What does 95% or 98% Assembly Mean? What do I need to assemble if shipped in crate?

For shipping safety, most vehicles cannot be fully assembled prior to delivery.

Minor assembly is required—this typically includes installing mirrors, connecting the battery, adjusting handlebars, and other small components. Before operation, please ensure all screws and fasteners are tightened, engine fluids are at proper levels, and the battery is fully charged. Your factory warranty remains valid right out of the box.

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