some guy locally put a yz 125 in and it blew, they said the blaster was too heavy for it. it was faster before it blew... he's selling it for like $1500 after it's running I believe... I'd put a larger motor in not a smaller, but that's a specific 90 built to stay within a specific class.. but yeah, I would imagine if u could make a yz250 motor fit or something it would be badass and not too heavy for the motor..
I don't know alot bout bikes so maybe it was user error but it sounded logical at the time lol