The bimetal spring is brittle. Try to bend it and it will break. Use a thin cutoff wheel in a Dremel tool to cut a slot in the flap valve shaft if there's not one there already. The spring should be wound enough to overcome the counterweight on the other end of the shaft and hold the valve into position to route exhaust gas up and around the intake passage diring warmup. Heating the spring with a propane torch should allow the weight to move the valve to the "open" position- - - -same as what happens when the exhaust manifold comes up to normal running temperature.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!