[JP Noonan]

The 914 has a "stepped" flywheel. Two surfaces have to be machined, the surface the disc contacts, and the surface the PP mounts to. If not done correctly the PP will sit further away from the flywheel surface and won't exert enough pressure on the disc.

I haven't been able to locate the min specs for a flywheel, but if it is cracked, blue, or the ridges can be felt with a fingernail it needs machining (cracks and bluing can mean the flywheel is beyond hope). If it is machined too much the flywheels bolts can hit the disc, I've seen bolts filed down a small amount to get a little more clearence. Filing them too much and the bolts will stop doing there job though, which is a bad thing.

Stepped flywheels cost more to machine, but most any shop can do it. PP's can only be machined (to my knowledge) by a rebuild facility, as for the 320 grit, I like to use "Scotch-Brite" pads, they get the rust without removing as much metal. After all sanding/machining use large amounts of brake cleaner and lint free towels to clean the surfaces right before install. Even fingerprints of oil can contaminate a clutch disc.