H-D Aermacchi 39984-69P, REAR CHAIN ADJUSTER ASSEMBLY Adjuster Body

Perhaps you missed the article on the ‘Threaded Shaft’ for the Harley-Davidson Aermacchi part number/description of ‘39984-69P, REAR CHAIN ADJUSTER ASSEMBLY’? We are going to do a very brief look at the ‘Adjuster Body’ because most of the story has already been told in the ‘Threaded Shaft’ article.

The rear axle adjusters of Harley-Davidson / Aermacchi 350cc street bikes, along with the racing bikes of 250cc CRS/350cc ERS are called ‘39984-69P, rear chain adjuster assembly’. This part is an assembly of 2 other parts, a threaded shaft and the adjuster body, welded together. These sub-parts that make up the ‘39984-69P, rear chain adjuster assembly’ are called:

39984-69P#Shaft#, 84-69P, REAR CHAIN ADJUSTER ASSEMBLY Threaded Shaft, and this decodes into:
- Title for the drawing/BOM: 84-69P, REAR CHAIN ADJUSTER ASSEMBLY Threaded Shaft
- Part number: 39984-69P#Shaft#
- File name of CAD files: ‘39984-69P#Shaft#, 84-69P, REAR CHAIN ADJUSTER ASSEMBLY Threaded Shaft. SLDPRT’
39984-69P#Body#, 84-69P, REAR CHAIN ADJUSTER ASSEMBLY, and this decodes into:
- Title for the drawing/BOM: 84-69P, REAR CHAIN ADJUSTER ASSEMBLY Adjuster Body
- Part number: 39984-69P#Body#
- File name of CAD files: ‘39984-69P#Body#, 84-69P, REAR CHAIN ADJUSTER ASSEMBLY Adjuster Body.SLDPRT’

Naming convention details are located here.

[irp posts=”441″ name=”Naming conventions for Aermacchi / Harley-Davidson project”]

The shaft has a 10mm thread. The DIN 934[2] standard gives good parameters for this thread. This nut is 17mm across the flats, and this does not follow DIN. You can read more about the nuts, in brutal detail, on another article on this site called ‘Harley-Davidson Aermacchi 7801P NUT, 10mm’.

Figure 1: 39984-69P#Body#, REAR CHAIN ADJUSTER ASSEMBLY Adjuster Body

The adjuster body has a 6mm diameter hole that accepts a press fitted threaded shaft. After these 2 parts are assembled and welded together, they make the ‘39984-69P, REAR CHAIN ADJUSTER ASSEMBLY’. See the pretty picture in Figure 2, below.

The hole in the ‘adjuster body’ is clearly visible in Figure 3.

We will update this article when the 3D CAD and 2D drawings are finished, with links to these CAD files. Here is a small taste of the CAD, below. Note: All values are nominal values.