HP Rating on the older twins

[Tyler33]

Do any of you guys know or know where I could find the hp ratings on the older bikes (400-500).  Id like a small twin to put into an atv frame that has pretty good power and everything.  Thanks.

[Blingmasta]

How old is old? I know that back till 89 the 500's had 40 hp

[Tyler33]

Yea thats what I was looking for.  How did the 450s and 425s compare and how much do you think the motor itself weighs?  Sorry for all the questions.

Tyler