Ok I had a issue where my upholstery on my set had gone away from the metal base of my seat due to the base rotting away. This is a common problem, You can also use this guide if your upholstery has torn near the bottom of the base.
What you need...
- Plenty of Beer and Rock Music e.g. AC/DC or Guns N Roses. If your a lady drink wine spritzers
- A buggered Motorbike Seat
- Cable Ties (Medium Length) You can use string...but I reccomend using cable ties as they will last longer.
Ok...
First take out the seat and flip it over on a desk or what ever.
Here is the damage on my seat...

As you can the upholstery has gone away from the base as the metal has rotted away...
(If your seat is torn you can strech the upholstery down and over the base and pierce a hole in the upholstery... works just the same)
Get a cable tie and thread it through the hole where the upholstery was originally secured. Obviously if you dont have a hole pierce one with a philips screw driver. Dont do it too close to the end of the upholstery. leave about just under a cm of gap to insure nothiong tears it self apart.

Repeat this for the other side....

now get one of the cable ties and create a hoop. Make sure u dont make it small make it so the cable tie just grips together.... don't tie it up yet..
Get the other side loop and thread it thru the hoop you just made and make another hoop.

Now tighten the hoops equally. This part requires your own judgement. What you want to aim for is to tighten the hoops so the upholstery just starts to pull it self together. The reason is for this is because when the seat is put on the bike the hoops will be pushed upwards and tighten them selves in the process. If you make it too tight and not enough slack it could just snap the upholstery holes.
to give a rough idea... look at this photo... You want it so you can push the ties to the seat. then you got a good idea what the seat will be like when put back on the bike. if it is too slack... tighten it.. if it is too tight cut one of the hoops and try again.

Now repeat for all the others...
and you should get this...

If for some reason you can not create or have a hole in the upholstery on the other side of the seat loop the tie to the loop next to it and of course on the other side hoop...

Once completed test it out by pushing all the ties down to the seat. then make any adjustments etc etc.
Now you tested it cut the excess cable tie and refit to motorbike.

Sorted.
hope this helps. cos it took me a bloody hour to make
oh yeah by the way, this only took me abouyt 15 minutes. and had a a great outcome.
