Removing stuck thermostat covers?

[Walkers Edge]

First time removing thermostats on my 98' yamaha 200 SWSII; When i went to remove the 2 thermostat covers the bolts came out fine but the covers were stuck.

Without knowing exactly how they slide off I was hesitant to torque them.
Can anyone provide some direction or tips on how to get these covers off without damaging anything?

Thanks!

 

[Grog]

They're just stuck, tap then with a soft mallet or gently pry them off.

 

[Walkers Edge]

I assume the "lip" on the cover is probably no more than 1/4" with a gasket?

 

[gw204]

I put a small piece of wood against mine and hit the wood with a regular hammer. They popped right off...