The point you need to check 1st is on the rear sproket, Grab the chain at the rear most point of the sproket, and try to pull it straight off the sproket, if the chain comes far enough off the sproket that you can see the ends of the teeth on the sproket, then you need a new chain. The next thing to measure is the tension. Hold the chain on the bottom run (that feeds the rear sproket) in the middle of the two sprokets. Then move it up and down. Most bikes shouldn't have more than about 3.5cm of slack. Between 25mm and 35mm is normally perfect, HOWEVER check your manual for the exact tension settings, as there are variations. Even the owners manual should state it. This will give you some details, like what torque to lock up the rear axel with: http://www.zxrworld.co.uk/Manuals/L%20M ... er%201.pdf One final tip if you can't find out exactly how tight your chain should be is to get a friend to sit on the bike (heavy person) so the swingarm is then putting the most tension on the chain possible. At this extent there should be a tiny bit of movement up/down, and the chian shouldn't be so tight as to restrict swingarm movement, otherwise you'll get advanced wear and drag, damagin your sprockets, chian rear axel and drive shaft. (you really don't want to mess up that last one). If I was you i'd ring up a local dealers and check the tension details with them. All the best, Bullet5.