Cannondaleriders

Cannondale released an "update" kit for this...
It is called an engine mount update kit and is basically a spacer that goes in between the engine mounts and is held in place with a terribly long bolt.
Due to manufacturing tolerances, it is wise to add a few extra shims between the engine case and the frame rail. You'll see the tolerance when you get the kit.
There are now quite a few versions out there, I'd suggest you send Haydug a PM and he'll help sort you out.

Good luck!

Sorry to hear that, it seems every Dale rider goes through that problem with their machine. Thats the bolts that are replaced with the stage8 kit, everyone talks about, its just a shame you found out to late. As for spending 2k to fix your motor try calling atk they had some complete motors for around 2400.00 all together, you could get and add the stage8 bolt it in and be ready to ride and have your old motor for spare parts. Or try contacting Haydug he's very good at repairing problems like yours and might have some parts to help you out. Good luck.

$3000!! wow, my son has his girlfriend's 450 motor for sale, cartriage plate bolts safety wired, ran this last season with no mechanical problems. He needs 2 grand for it, extras are included. PM me if interested.