frosted intake

[stroker800]

   I realize I should know this ,,,but I don't know 100% why....I ran a SU carb on my shovel with the elbow intake..It hangs the carb way out 6"-8" off the motor ...After riding a while the intake would frost over,,icey to the touch...The bike ran like a raped ape ,,,the only thing I didn't like was rubbing on my knee. I figure there is an answer with you guys,,,thanks
Dave

[motorplex88]

I've had this happen on some old super modified stock cars [six cylinders] where the intake hung out away from the engine. The thing would run really! good and then would burn a piston. This happend a couple of times till finally I got to pits fast enough and got the hood off to find the intake frosted. Got some engine heat going to the intake and problem was cured. Took awhile before I could figure out why the motor was going lean. Food for thought. 

[triumphbruce]

The venture effect.the narrowing and widening of the carb throat
slows then speeds the intake air causing cooling

[jimrookie]

 I had a hot rod Bug motor with a high rise manifiold and large carb, no heat riser so any time it was 45 or colder the carb and the manifold near the carb would turn into a frosty
block of ice then it would start spittin and sputtering and loose power