Husky Carb pre-heat flap/door-How critical is temp?

[outdoortype]

  I read in the manual for my Husky 359 that when your cutting at or below 32 degrees F that you're supposed to open the flap/door in the cylinder cover to allow preheated air to pass into the carb & filter dept. to keep them from icing.  The air temp has varied a lot the last few times I've cut.  Yesterday it was 40-45 degrees F and I cut for 45 minutes before I realized that I left the flap/door open.  The saw ran fine.  I'm just wondering if I did any damage? Do I need to keep opening/closing the flap until the weather stabilizes? Thanks for your input.

[Ianab]

It's not critical, it's more a summer / winter thing. If it's real cold, you want to suck warm air off the engine to stop the carb icing up. If it's a hot day you want the coolest / densest air you can find to keep the mix right and the power up. At 40 deg neither setting should cause a problem.

Ian

[Minnesota_boy]

In years past, there were no flaps and most of the time, carbs didn't ice up.  It takes certain specific conditions for carb icing to be of much concern.  On the other hand, having air preheated isn't much of a problem until the outside air is quite warm and I don't believe that 45 degrees fits that.

If I felt that carb icing could happen, I'd open that flap to preheat the air, but I wouldn't worry overmuch if I forgot until I noticed the saw running poorly.

The 32 degree thing is a part of the condition that is required for carb icing, so you don't need preheated air at temperatures above that.