Harley-Davidson ® FXST/FLST Series (Softail) (1984 - '90) Motorcycle Batteries

Reliability for the Original Softail: FXST/FLST Battery Guide

The 1984-1990 Softails are the machines that brought Harley-Davidson back to its aesthetic roots. Because these early Evolution engines are often equipped with high-torque starters, they require a battery with a high discharge rate. The Motocross Platinum AGM series is designed to meet these specific electrical demands, offering a factory-perfect fit for the oil-tank-integrated battery compartments of this era.

The Advantage of Motocross Platinum

The Motocross Platinum YTX20H-BS is manufactured by Yuasa, the industry leader in powersports batteries. It is the high-performance equivalent to standard 20-series batteries, offering higher cold cranking amps (CCA) and better recovery after deep discharges. For owners of early Softails, this means more reliable starts and a longer overall battery lifespan compared to standard aftermarket units.

Frequently Asked Questions

Does this battery fit the first Fat Boy and Heritage Softail models?

Yes. This category covers all FXST and FLST models from the 1984 introduction through 1990. This includes the original Softail Standard, the Heritage Softail Classic, and the legendary 1990 "Grey Ghost" Fat Boy. These models utilize the high-performance 20-series footprint (GYZ20H / YTX20H-BS) for maximum reliability.

Is this an upgrade over the original YB16-B-CX battery?

Yes, significantly. The YB16-B-CX was a traditional "flooded" battery that required regular maintenance. The Motocross Platinum YTX20H-BS is a modern Absorbent Glass Mat (AGM) battery. It is permanently sealed, maintenance-free, and much more resistant to vibration, which is a major factor in the solid-mount Softail frame.

Can I use a Lithium battery in an early 80-cubic-inch Softail?

Lithium (LiFePO4) is a popular upgrade for riders looking to maximize cranking speed and reduce weight. However, on these vintage models, it is important to verify that your charging system is functioning correctly to protect the lithium cells. If you do switch to lithium, ensure you use a Lithium-specific charger for maintenance.

How do I prevent my battery from dying during the winter?

Because early Softails have minimal electronic "parasitic draw," they hold their charge well. However, chemical sulfation can still occur if the battery is left partially discharged. We highly recommend using a smart maintainer like a Battery Tender to keep your battery at peak voltage and ensure it's ready for the first spring ride.

Model Fitment Reference

This category is the definitive source for batteries fitting 1984-1990 Harley-Davidson Softail models, including:

• FXST / FXSTC: Softail Standard and Softail Custom.
• FLST / FLSTC: Heritage Softail and Heritage Softail Classic.
• FLSTF: Fat Boy (1990).
• FXSTS: Springer Softail (1988-1990).