Hi guys done my intro and was pleased how welcoming ppl on ere are so here's my 1st question.

I noticed my chain looked abit saggy today on my ybr 125 and was wondering how easy it is to tighten it.

Hope someone can help.

If you have the owners manual or even the owners workshop manual it should give you all the details you need in there, if not then loosen the 2 adjuster nuts off at the back of the bike swing arm, undo the large spindle nut that runs through the rear wheel, make sure it is loose, then tighten the 2 nuts up on the rear adjusters until the slack has gone, do not over tighten it as this will lead to chain and sprocket wear, also make sure you adjust both sides the same as this will also wear out the chain and sprocket, when your happy with it all being lined up tighten everything back up to the required torque. Do you know what the slack should be? most bikes have at least some slack in them usually measured from mid way between the front and rear sprockets, mine for instance is 25mm from the centre point, if you don't know DON'T guess, find out and then adjust it, look up a youtube vid if that helps, some can be really good.http://youtu.be/kCK5339cSpQ

This vid might help.

Sound advice above . If the chain has some mileage on it check to see if it has a "tight spot" . If you spin the back wheel with the bike on the mainstand (minding your fingers , or anyone's helping you ) , and watch the chain you'll see it tighten and slacken . Adjust it at the tightest part . If it's very bad a new chain and sprockets is best and will make your bike feel much improved . If the sprocket teeth are very sharp or hooked , they're well knackered .

Thank you both for ur advice it worked a treat I left a little bit of slack on and it's running a lot better now

According to Haynes:

slack should be between 200 and 300 on the YBR (2005 to 2013). check multiple places on chain.

chain stretch limit is 191.5mm (measure between 1st and 16th pins)

Sound !