250-500cc Chain Stretch

I have an 09 WR250. I have to adjust the chain after every ride because the chain is stretching so bad. Wearing sprockets as well. I adjust the chain with a Motion Pro adjustment tool and than check it with a micrometer. Could the swingarm be bent and if so how do I tell? Any advice would be helpful. Thanks Mad Mike

What type of chain?
What type of riding terrain ie. mud, sand....?

Cheap chains stretch quickly as do most non o-ring chains.

Adjusting the chain too tightly will also cause the problems you are describing.

get yourself a good quality chain like D.I.D gold chain and supersprox stealth sprockets and you will get long life out of them

X2!

Chains can be adjusted with a ruler, if not just by feel; you definitely don't need a micrometer.

I would be concerned that you are setting the chain too tight.

I have worn out many good quality O-ring chains, but have never had one show any signs of stretch. Ussually the rollers wear out long befor they stretch.

I'm using an O-ring chain. I use the micrometer to measure the distance of the axle stops compared to the swingarm. The tension is set according to the manual. The chain will not ride on the slide on top of the swingarm but cuts it at an angle. Has anyone heard of bending a swingarm?

Measure from the centre of the swingarm pivot to the axle on each side to make sure they are the same. Measuring the axle stops may not be accurate (you will know after you measure from the swingarm pivot). You can also look along the length of the chain from the rear to make sure the sprockets are aligned.

Use some tiedowns over the seat to compress the suspension to where the chain tension is tightest and adjust so there is some slack at that point.

Line up the wheel/chain/sprockets, by eye. Forget about measuring the swing arm slots. If you cant get it all lined up by eye, then consider your swing arm may be bent.

I've still got the stock chain with 300+ hours on my 09 wr250,but I've been through 3 sets of sprockets. Does anybody know what chain came on the 09?

+ 1 The only way.

Super sound advice! I would add that the chain is at it's tightest when the rear axle, swingarm pivot, and countershaft are on the same axis (straight line through them all). No matter the bike this is true, it is looser as the axle travels above or below this axis. So use a tiedown to achieve this or a jack under the bike with the top shock unmounted. Then, adjust the chain to have minimal play, almost tight. Next allow to extend, and put on stand. Check chain slop by finger-feel or measure or make a go-nogo block. You will always have the chain perfect now and it should stretch less.

This is useless on a worn chain, they stretch WAY unevenly.

By all means spend good money on a chain. More expensive is generally better. non o-ring chains don't wear faster than o-ring chains until the run dry, keep em well lubed, pack chainlube if your ride takes you farther than the lube lasts. A worn (stretched) chain will quickly waste new sprockets, keep the chain fresh and even aluminum sprockets last forever.