1994 XTZ 660 front fork preload adjustable?
 

Is it possible to adjust preload on the front fork on a 1994 XTZ 660? Or do I need to change the springs to make it less saggy?

Fork adjustment
 

As far as I remember (I sold mine 2 years ago) there is no built in adjustment but all front forks can be adjusted by making a new spacer tube to go under the cap and above the spring. This can be aluminium or PVC tube of diameter a little bit less than the inside of the fork tube. Based on my experience with sagged springs I would make the new spacer about an inch long (or an inch longer than any existing spacer).

Having said that sagged springs are not cured by spacers - all you do is lift the front end which compensates for the sag - but the springs have less compliance. Use them as a short term fix until you can afford new springs - which aren't overly expensive (about $200 in Australia) - and change the fork oil at the same - you'll be amazed at the difference.:scooter:

new wilbers springs is well under 100euro from ebay.de

Thanks guys, I'll try the quickfix as a temporary hack and order some new springs. How about the rear shock, any adjustments I can do there?

On the rear you can increase spring preload with the big metal nut the spring is sitting on. Undo the locknut, set the big one to your preferences, tighten the locknut.
On the bottom of the shock you have small plastic ring for rebound damping adjustment. Just turn it around, it should (but most of them do not) click when in one of the five positions marked on the ring with numbers, looking from the left side of the bike. 1 - no damping, 2 - normal, ... 5 - full damping.