I am looking for a copy of the 1986 377-447-503 owners manual

I am tryng to determine the correct compression ratio for a 377UL motor

I have the 1990 owners manual, and also the 92 and 94 revisions of it.
The 377 is listed as having compression ratio of 11.6 to 1

A well known (but will remain unnamed) site says something significantly lower

I am trying to determine if there are really two ratios - or if the site is in error. Two ratios would mean my rebuild project might have me looking for different heads

Tried e-mailing website "contact-us" link - no reply

There is an earlier -1986 - version of the manual available online. But it is only a partial copy - the technical data pages are not there.

Any old timers out there have a copy of the 1986 manual ? - or any other official Rotax document showing a compression ratio other than 11.6?

Thanks