On my Yamaha TZ350G the exhaust pipes are modified so that they can accept the later (stronger) springs.

As the old spring and bolt system is a little vulnerable Svend Andersson (our Danish YCRT rider and a wizard with torches and other tools) modified the pipes by welding 2 loops to both. I can use now the modern springs from the 1992-2000 TZ models.

Modified TZ exhaust attachment