1998 zr 500 I bought from my brother in high school.
He had it for a couple years, didn't give him trouble aside from a crack in a cylinder that leaked coolant on the outside. He went off to university so I bought it and discovered the bulkhead had so many broken welds there were only two welds remaining that held the front suspension on. Rivets on the belly pans is what kept it together.
I stripped it down, replaced the bulkhead. Replaced the cylinder. Decided to upgrade the sled when I put it back together. Needed a new clutch, I installed zr3 front suspension, added new running boards, did post forward mod.
Worked on it all summer when I was 16, got it running for winter. Took it for a ride, and the damn thing started burn coolant 5 miles from home. Towed it home, put new o rings on the head. Same issue. That's how I found hcs, discovered the head was warped. Put a new head on, was running out if money though. Ran good, then it would intermittently die on me and leave me stranded. Fucking stator was going! I couldn't afford to replace it, so I parted the sled out as I needed money for college.
I've had reliability worries ever since. I also have a very kean sense of smell for antifreeze now.