When I'm driving my 1980 Motobecane Moby for a long distance and then go to stop it sticks up in second gear, and the engine comes out of it with a harsh pull and loud "klunk". When the Moby goes into 2nd it pulls the engine up toward the frame - on some sort of spring. When I ride it for a really long time at full throttle it has actually stuck up there and i've had to knock it down by putting the kickstand up - which pushes on the muffler to push the engine down, not something i want to do too often.
So has anyone had this problem had this problem? Any ideas on what is making the engine stick up in 2nd gear like that?
It only happens when I travel for a distance, so I thought it might have something to do with heat...