Ultra Bee Primary Chain Drive Racing Kit With 420 RK MXZ Sealed Chain!

For serious off road and moto racers the non-sealed RK MXZ chain kit is the most efficient kit with the least amount of parasitic drag.

• More Efficient Than Belt
• Better Acceleration
• Longer Run Time
• Easy Maintenance
• Similar To Stock Gear Ratio
• Chain can be replaced without removing the swing arm

Be sure to include the DirtyBike Ultra Bee Swingarm Alignment Tool! Makes the job of aligning the mid shaft shaft and swing arm much easier. 

Note: If you are planning to use this kit with the EMBX XUB-80 motor the front sprocket will require modification. Please contact us for more information. 

Swingarm alignment tool

Buyers and Maintenance Guide

Please verify your bike model and year before purchasing. If you have questions about fitment, contact us at support@elektrischesracing.com or use the chat below — we’re riders, and we’ll help you get the right part.

Installation requirements vary by product and vehicle. Review the product description and available manufacturer instructions before installation. Contact support@elektrischesracing.com for fitment or installation questions.

Will this fit my bike?
Check the product title, description, and fitment details above for compatible models. Not sure? Email support@elektrischesracing.com or use live chat and we’ll confirm before you buy.

How long does shipping take?
Availability and estimated ship time for this exact item are shown above, next to Add to Cart. Processing and shipping times vary by product and fulfillment partner. In-stock orders fulfilled directly by Elektrisches Racing generally process within 1–3 business days; supplier-shipped, made-to-order and backordered items can take longer. Shipping rates and any available free-shipping offers are confirmed at checkout.

Do you offer financing?
Yes! Shop Pay Installments and Affirm are available at checkout.

What’s your return policy?
Eligible unused items may be returned within 14 days of delivery, subject to the store’s refund policy and exclusions. Baja Designs, Warp 9, GUTS Racing, Sur-Ron OEM and KO/EBMX products are not eligible for standard returns or exchanges through Elektrisches Racing; manufacturer warranty claims are handled by the manufacturer — see our Refund Policy for full details.