Hi I have a 1989 polaris Trail boss 250 and i can't figure out where the stator plate sits it has no notches it is brand new and the quad will pop at high rev

 

May not be the stator plate timing that's out. Pull the black wire from the reverse over ride module at the terminal board and see if that helps first.They can fail and cause problems in forward range also.Item#33 on the parts break down. If this doesn't help,the only way to accurately set timing is with a timing light. 25 degree mark on the flywheel @3000 rpms like shown in this section out of the manual.The 250 and 300 engines had the same timing.

 

How do I check the rpms

 

You'd need an rpm meter along with the timing light. Borrow one or you can get them for 8-10 bucks on ebay,amazon.