Alternator Belt Tensioning Tool

[Redbeard]

I'm pretty sure something similar will have been posted somewhere on the site even though I can't find it. But just in case it hasn't:

As I was going to be doing bugger-all over Xmas I decided I'd service the bike and change the alternator belt as it would due for replacement in another 1k or so miles. Being as how I'm a lazy git I thought I'd get one of those nice alternator belt tensioning tools (special tool 12 3 551) so I could do the job without mucking around with the fuel tank etc, etc.

After much searching I finally tracked one down at a US BMW site. Great... except for the $42 + shipping + UK tax for what looks like an Acorn Nut with a spring (anyone remember Zebedee?). No way was I stumping up that amount of cash for that, I may be idle but I'm not rich! Time for some inspired thinking

After a suitable amount of inspired thinking and a little lie down, I came up with the gizmo pictured below (assuming the attachments worked).










All you need to make your very own are:

1 x M8 x 25mm thread connector of the type used for tie rods
2 x M8 nuts
1 x M8 bolt of suitable length or a length of M8 studding. (If you use studding, thread the connector onto the alternator bolt leaving a bit of clearance between connector and alternator nut, then wind the studding into the connector until it contacts the alternator bolt and set it at this distance with Araldite or similar.
1 x spring of a suitable size, I used an old clutch spring, I think it was from either an LC Yam or Suzi GS
1 x M8 flat washer if you use studding and spring version pictured

You can do without the spring if you don't have one, its just another way to stop the alternator bolt getting pushed out.

I hope you find this usefull when/if you need to do your alternator belt.

 

[Grim Rider]

Not sure what this does? Have changed alternator belt three times on my GS, never had to do anything to tank, just removed crash bars, alternator cover, undo three bolts to release belt, put new belt on, tension it by using tyre lever against alternator and tighten up bolts to same location as came off. Not had any problems in 100k - sure followed one of Steptoe's how to guides first time I did it.

 

[Steptoe]

Psssst. Look in the sticky "Tips and tricks" at the top of the section.

Picture "how to" HERE.

 

[Welshman]

I have designed a lot of industrial drives with poly vee belts and in my experience...

1. Tensioning is best not done by deflection, but by extension, you mark a fixed distance on the belt, fit belt then tension to required extension (dont have figures with me for a 4pk).
2. The 1/4 turn method was for simple vee belts not for for poly vee they are too wide and flat you can damage the outer ribs doing that.

I have some of these tensioners sitting in my tool box, never used yet by me, they are brass and bear that funny stamp we used to see "made in england".