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Service bulletin 1HD-X3H4B-12

A bulletin is a manufacturer's communication to its dealers, as NHTSA indexes it. The summary is NHTSA's. The document is the manufacturer's: read it at NHTSA. A bulletin is not a recall, and listing a model year does not mean every vehicle of it is concerned.

The communication, as NHTSA indexes it (as of 2026-10-19)
TypeService bulletin
NHTSA id10125153
Published by NHTSA2017-12-14
Manufacturer's number1HD-X3H4B-12
Manufacturer's date2017-11-15
NHTSA componentPOWER TRAIN; ENGINE

NHTSA's summary

SERVICE BULLETIN M1450: MILWAUKEE-EIGHT EQUIPPED VEHICLES - LOSS OF POWER OR HIGH ENGINE BRAKING. Purpose: 2017 and 2018 model motorcycles equipped with a Milwaukee-Eight engine can experience a condition known as sumping during extended periods at high rpm or under heavy engine load. This bulletin provides the diagnostic procedure for determining if sumping is occurring.

The document

The document is the manufacturer's. This site does not hold it. NHTSA files a document at one of these two addresses; we have not asked NHTSA which.

Components

Engine, Transmission and driveline

Vehicles listed
HARLEY-DAVIDSON FLHP2017 to 2018
HARLEY-DAVIDSON FLHR2017 to 2018
HARLEY-DAVIDSON FLHTCU2017 to 2018
HARLEY-DAVIDSON FLHTCUL2017 to 2018
HARLEY-DAVIDSON FLHTCUTG2017 to 2018
HARLEY-DAVIDSON FLHTK2017 to 2018
HARLEY-DAVIDSON FLHTKL2017 to 2018
HARLEY-DAVIDSON FLHTKSE2017 to 2018
HARLEY-DAVIDSON FLHTP2017 to 2018
HARLEY-DAVIDSON FLHX2017 to 2018
HARLEY-DAVIDSON FLHXS2017 to 2018
HARLEY-DAVIDSON FLHXSE2017 to 2018
HARLEY-DAVIDSON FLRT2017 to 2018
HARLEY-DAVIDSON FLSL2018
HARLEY-DAVIDSON FLSTB2018
HARLEY-DAVIDSON FLSTF2017
HARLEY-DAVIDSON FLSTN2017
HARLEY-DAVIDSON FLTRUSE2017 to 2018
HARLEY-DAVIDSON FLTRX2017 to 2018
HARLEY-DAVIDSON FLTRXS2017 to 2018

Listing a model year does not mean every vehicle of it is concerned: the document says which.