Well I've always used a flywheel puller and had no troubles.. Then my bike started to stumble sometimes rite b4 it got up to normal temp. All I had to do was hit kill switch and kick it over and it was fine, weird rite? That happened for about 2 months of hard riding.. So recently it intermittently miss fired on one side,, put a new plug in and cleared up, rode 3 times and acted up again.. ( since I did my top end maybe more than 60 hours ago I NEVER fauled a plug.) So figured top end needed refreshed. Nope. Good compression so after 9 hours today of trying to clean and check every connection I can clearly point my finger at that damn flywheel... Sry for the story but there's really no " symptoms " of how a flywheel will slowly take a shit!