Hi i have a 2008 yamoto 250 quad that keeps spitting the chain when under load put new tenioner spring on it didnt work chain could be stretched as it keeps doing it front and rear sprokets are new and theres when on load chain pushes loose coming from rear sprocket to front any ideas would be awesome

 

There should be an adjustment to tighten the chain. The tensioner is just for taking up the slack you leave in the chain and help quiet the driveline down.

If the chain is tight when sitting, the motor may be moving under load and letting the chain slack.

 

In addition, if the sprockets are new, it should get a new chain also. In general a set of sprockets and chain wear out together. New sprockets with stretched older chain is a recipe for premature sprocket wear. If it stretched past spec it will be more likely to come off even if you can get it tightened properly.