Sounds like you've siezed up your motor. Shouldnt be more than $200 if you can do the labor for a top end rebuild. Also so this doesnt happen agian i would look at a few things. Your oil weather you have a block off kit and your premixing or you have the injector still running. Make sure your using the right kind and mixing the right amount if you have a block off kit.

 

Yamaha dealer said they would fix it for 200 if the crank or rod isn't messed up i dont have a block off, the injection seems to work okay, she was running good i guess it was smoking a little like a 2 stroke and the plugs never got oil fouled off white from heat. The reason I think it locked was because it was locked up when i got it and i had the cylinder honed out and we put another STOCK piston in it I think the cyl was honed too much and there was a tiny bit of piston slap but they told me that the only way to fix that was a bore and new os piston, so I would have to do it all over again they told me just to ride it till it either locked up or had too little compression to run anymore and then fix it. so I guess thats where I am now but I thought having Yamaha do it this time for 200 to have them bore it out and put a new piston and rings and clips and pin in it was a good deal hell I paid 100 for the piston the last time and didn't do any boring so 200 is fair I think I will keep you all posted on what all went wrong LOL i have a feeling I will just end up giving it away and looking for another quad (4 stroke this time hell with a damn 2 stroke I hate them).