A weird issue.... Help!

[MotReklaw]

I too ran the vent tubes into the K&N filter, per the advice of a rotax mech... No problems

[Jerrytex]

This got to me thinking about my vent tubes. I have the Carb box that came from Kitfox. It mounts on the gearbox and has two scat tubes that run to the carbs. Anyone run the drain tubes back to this airbox? It would be extending the tubes considerably.

Page 50 of the Rotax manual addresses this and talks about having the drain tubes connected or else there is a chance that they could drain on to the hot exhaust.

http://www.ultralightnews.ca/rotax91...tionmanual.pdf

[GoingHawgWyld]

Jerrytex,

I don't think it is the length of the tube that is the issue. The reasoning is that the longer the tube the greater chance you are placing the end of it in a location that is of a different atmospheric pressure than that of the carb opening. I would think running them to the air-box is good as your carbs are also connected there and should be the same pressure.

This morning I looked at my friends set up that was having the issues and when the cowl was removed it was obvious! He ran his vent lines into a metal tube that ran down the firewall to the bottom of the plane. An obvious pressure differential. So we poked a hole in his K&N filters and put the vent tubes in there. Problem solved! Ran excellent! Thanks for all your help! He said it was like getting a new plane! He has been worried about this for the last 250 hours! He probably is very fortunate that he did not have an engine out at some point...