Timing issue

So I have a 98 grizzly 600 I bought knowing she was messed up so tore the top end down discovered a wrongly installed broken timing chain guide causing noise also the clutch was toast replaced clutch and drive belt no problem but when putting my top end back together no matter what I do when the fly wheel timing marks are lined up my pistons not even close to tdc and I've rotated it 15 20 times what can be done I've never encountered this