carb icing?

[ScottieJ]

out of the two engines I have run, 970cc and 1590cc vit lumps, both with standard carbs. I have found that if you run anything other than standard air box with the option of the hot air feed you will suffer from carb icing, i was running just a k&n cone filter on my vit for a bit and it suffered from serious carb icing issues on motorway runs even when it was wasnt that cold and even more when it was raining. I put it back to the standard air box and even without the hot air feed it improved! on the 410 i had a rubber sleeve to block up the hot air feed when wading and offroading as it's not as bad at slow speeds, just when you are out on the road.

[Pugsley]

strange??? it dosnt seem cold enough to ice up,, (must be colder were you live), i had a thought, your snorkle, does it face into wind, ie forwards. that would give the efect of ram air. if i were you, disconect it at the carb, then see how she runs!.
andy.

It doesn't have to be particularly cold for carbs to ice up - about 5-7 degs C with 60%+ humidity will be ideal for this if the carb is prone to the condition. When I used to ground run aircraft with gas turbines fitted it was mandatory (in peace time) to refer to a graph if certain atmospheric conditions were present to ascertain whether the engines could be run. If you ever want to see icing up - watch an old aircraft air intake (most are heated today) in the described conditions - about 100lb accumulation of ice in 5 seconds.

[jutwit]

cheers guys, i will have a play about with the various options and let you know what happens.