When my ST2 / ST4s – based track day bike project was cancelled, I was left with some useful ST4s parts, specifically an alu swing arm to replace the M800 Dark steel item. Apart from a slight weight advantage, there is a certain bling factor,
PC120024 by
torbjörn bergström, on Flickr
However, when installed, the same problem made itself obvious as with my now-sold M900: a really sloppy fit of the linkage bolt in the swing arm.
Again, with the vital access to my mates workshop facilities, I decided to do something about it. Some special tools had to be made, but nothing very special, really:
Guided countersink tool (whatever that is in English), adjustable reamer, some suitable extensions, a brass bush, and a drift for the bush.
P3040008 by
torbjörn bergström, on Flickr
20161125_215952 by
torbjörn bergström, on Flickr
The rest is pretty basic:
Drill out the bearing bore in the swing arm with the guided countyersink;
P3040005 by
torbjörn bergström, on Flickr
P3040004 by
torbjörn bergström, on Flickr
P3040003 by
torbjörn bergström, on Flickr
Install the bush (no picture, I´m afraid); a couple of 100ths press fit would suffice. Heat the swing arm with some torch or heat gun (take care not to set anything on fire) and press the bush in place. Or use loc-tite if the press fit is no press.
Ream the bush, increasing the diameter a little and testing the fit with the bolt after each pass. Take care to only ever run the reamer in the “cut” direction, running it backwards will dull it.
P3060001 by
torbjörn bergström, on Flickr
P3060002 (2) by
torbjörn bergström, on Flickr
Clean everything up, grease in the appropriate places, assemble and enjoy your solp-free suspension linkage.
