SV650.org - SV650 & Gladius 650 Forum - I've been told that the front forks go at about 30k

As a point of reference, the forks don't "go" on the SV, my SV (K2 SVS) Had 153,000 miles on 4 oil changes, original seals and progressive spings,that said there are three parts that wear and degrade over time/use.

1. Springs.

the forks come as standard somewhat budget by nature, however the basic design works well on the bike, however the spring weight is appropriate for about 10 stone or so any heavier and you'll get the infamous "knocking", so it's advisable to change them for something more suited to your own weight.

Replacement springs come in two basic types these being:-

Single rate springs - you buy them according to the weight required and they give a consistent performance along the springs travel range, the coils of which are evenly spaced (good as long as you have the right weight, but limited to that weight).

Progressive springs - these work within a varying weight range and provide greater resistance the more they are compressed, the coils of which get tighter along its length (covers a wide range of weights).

All springs will loose their "bounce" over time the dynamic range of progressives should be an advantage here so the standard (and single rate springs) will go "out of range" the quickest, but it's hard to say when as it depends on how the bike is ridden to a great extent, checking them should be part of your service schedule and if you can't tell performance has decreased then get someone you trust to check for you every year*.

2. Oil.

Fork oil is a work component, often overlooked but over time it will degrade.

Fork oil comes in different viscosities, denoted by a number 5W OR 10W and so on, the higher the number the "thicker" it is and makes the damping heavier.

Obviously active use and heat buildup will decrease the life, so once again it's hard to predict when this will need changing, but it should be checked every 20,000 miles or so (if it's grey and like water, it's passed it's best).

You can also vary the oil weight to suit your riding if needed.

3. Seals.

Basically a steel banded rubber seal to keep the oil in, as these take a considerable pressure when under load they require to be in good condition, fortunately they rarely just "go" and as you have one on each fork you'll be very unlucky to have both leak at the same time, however regular inspection for escaping oil above the seal should be carried out and replacement undertaken if that's found.

As the seal is by nature frictional it will wear, but under normal use this should be years before becoming an issue, poor maintenance of your forks allowing buildup or pitting will dramatically effect this as it will tear up the seal in short order, so care should be taken to clean the fork legs whenever possible**.

*you can remove the springs and measure the length to check they are within spec, if not they will need replacement.
** some aftermarket seals have been known to be less effective than OEM, so be aware sometimes a saving may not be as good as it first appears.

HTH

Cheers Mark.