Head, Racing, GX390, Large Port, High RPM, Honda Core

$229.00
$293.00

Large Port Ready-to-Go Race Head for GX390

with Genuine Honda Core

This head uses a Genuine Honda core for better flow, less porosity, and higher strength than aftermarket heads. Head may be fitted with either single or dual springs. Single springs are recommended for 306 and smaller cams; duals are recommended for 307 and larger.

GX390 heads have the options of 36mm, 38mm, or 40mm intakes.
*GX390 heads will fit GX340s.

We offer heads in two port sizes:

"Small Port, Torquer" uses small port castings to increase velocity and maximize low-end power at some loss of high-end RPM. These are the best choice for most applications.
"Large Port, High RPM" uses large port castings to increase high-end RPM power at some loss of low-end torque and reduced throttle response. They may provide increased cooling for endurance applications.

Product Includes:

Ported, and bead blasted head, milled to specs
Stainless intake and exhaust valves
Aluminum or titanium retainers
Split keepers
HD single or dual springs
Valve spring shims
3-Angle valve job

Increased milling increases compression, but may affect reliability. .120 not recommended

*Note: Heads are typically built to order. Please allow approximately 1-5 days before shipping.

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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Head, Racing, GX390, Large Port, High RPM, Honda Core

Frequently Asked Questions

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