On my '96 850. I pulled the air filter box to get at the dizzy. I started fooling around w/it and I sorta think that the flapper valve that allows it to suck hot air at warm-up and then cold air when hot is not working right. First, I ran hot water on the spring...nothing. Then I put it in the oven at 170....nothing. BTW, it is pretty hot when you hold it at 170. The flapper did not seem like it was any easier to push at 170 than when it was cold.

Is this a known problem area?

 

I checked youtube and there were several threads/videos on this...so it must be at least a small problem. I ended up wiring the flap open.