QMB139 39mm Cylinder Kit
39mm Stock Cylinder Kit for 50cc 4-stroke QMB139 engines. Includes cylinder, piston, pin, circlips, rings, head gasket and base gasket.
- Bore: 39mm
- Overall Height: 70mm
- Cylinder Sleeve Outer Diameter: 44.7mm
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.
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).
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.
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.