so i have to adjust my chain once in 3 weeks.....first i though i didn't tighten it enough but now i see the difference....i remember the last time i did it and it was wery tight (because the time before it had about 1 inch of play and that ended up to be 2 inches) and now it's very loose

could this be a old chain and it's normal for old chains to strech like this?
did i not adjust the wheel straight by looking at the markings on each side of the swingarm?
or should i stop accelerating/decelerating hard  :dunno:

i got a buddy who snapped 2 chains within a month and a half
they kept on stretching and eventually snapped
go figure he baught the cheap ones
i think they were like 40 bucks each
when one of them snapped he took at leat 5 teeth of his rear sprocket

and one more thing when you tighten the chain you should have a load on the suspension
the chain gets tighter as the suspension compresses

and old chains do stretch faster than new ones

Constant streching is a sign that the chain and/or sprockets are toast.

Replace it with a GOOD X or O ring chain and biting the bullet and changing the sprockets is a good idea too.

When you adjust check it in a few spots.  It might be tight in one and loose in another.  You have to find the tightest point and use that as your reference.  If you checked it at its loosest point one day and at the tightest point on another day you'll be thinking that it streatched a lot.  Even if the chain is old it's not going to stretch that much in a few wees unless you put on a tremendous amount of miles.
How many miles did you put on it 3 weeks?

wheelies and lack of lube/dirt are the biggest killers of chains and sprokets.  Lube will also keep the chain from over heating( threw a chain once, got blisters from the burn when i picked it up) heat will make the chain stretch faster and unevenly.

i average about 400 miles a week  :guns:
but i do lube the chain all the time

the killer must be the wheelies and racing with my buddies

go with an o-ring chain and some new sprockets and you will be fine