From idle to around 6K the engine is as smooth as one would expect from a rotary with an engine mount that's been soaked by broken OMP lines the past year or two and old Y-blocks. Anyway, above 6000 rpm the vibrations increase dramatically, it feels pretty harsh.

Now, what could be causing this? Something engine-management related, or mechanical causes?

 

How is your compression? Does it feel like it's misfiring at 6k and up, or just vibrating pretty bad? How about when it revs down, does it feel like it smooths out when you let go of the throttle from 7k down to 6k?

 

Clutch out of balance? Torn/super soft motor mount?

 

can you actually rev past 6k??

 

@ Jake,
-Yes it will rev to 8k, been there a few times.

@AGreen,
-Revving down it smooths out. I haven't tested my compression, but at idle the engine is smooth, slight vibration from the engine but no more than my mom's F150. I don't think it's a misfire, just hard vibration.

SpeedOfLife may be right, the passg-side front engine mount, as I said, has been soaked in oil since I bought her a few years ago. But, it may be wonky compression on the leading rotor. For the same three years, the 1 and 3 OMP lines have been broken and tied together with rubber sleeves. (I didn't know any better, first car, first Wankel, I'm playing it by ear)