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Service bulletin SB638

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 id11026941
Published by NHTSA2026-01-05
Manufacturer's numberSB638
Manufacturer's date2025-12-09
NHTSA componentPOWER TRAIN

NHTSA's summary

Service Bulletin 638 advises dealers to measure and replace the camshaft drive chain tensioner.

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

Transmission and driveline

Vehicles listed
TRIUMPH SCRAMBLER 400 X2024, 2025
TRIUMPH SPEED 4002024, 2025

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

Other bulletins for the same vehicles and component
COM3 - 327482026-01-05. Service bulletin. Dealer notice announcing the availability of Service Bulletin 638.