Question 503 carb compensator pipe.

[nickjaxe]

Hi guys I fitted a new compensator pipe to the carb on my 503 SC on
a British Mainair trike a few weeks back,

The one that's a U shape and goes to each side of the carb and has
two small vent holes in it,

As far as I know from the paper work I have, the pipe has to be
routed to a carm air zone out of the prop slip stream,

Now some of the guys at the field were I fly from here in the UK
have the same
trike as me but don't have the U shaped pipe but single pipes with
no apparent ill effects,

Can any of you guys tell me more about this pipe , should I be using
the twin single pipe idea on a trike that has a carb thats not in
the prop slip stream, its just that my trike had the u tube setup
when I bought it, and I am thinking maybe there only supposed to be
fitted to aircraft with tractor props, does it make any difference.


Nick.

[Morph]

On older model carbs there were two vent tubes, one coming out each side of the unit. The latest carbs have one vent tube connected to the two venting outlets - with breather holes in the center section of the vent tube.

Apparently in the older style of venting system air could enter one vent line and exit the other causing havoc with the float metering system. In other words the upwind side would have higher pressure whilst the downwind side lower. Therefor to solve this they insisted that the two tubes be placed outside of the prop slipstream. The new system prevents this giving a more stable fuel supply.

This new style of vent can be made from a piece of primer line and putting two side by side holes in the BOTTOM of the line in the center, these holes are about 30% of the diameter of the primer line. Too small and they will not allow the carb to breath properly.

[nickjaxe]

Hi Morph thanks for that mate, explains it very well,

Just one point the holes that you put in the pipe do they go right thru both sides of the pipe or just one side.

Nick.

[Morph]

Only 2 small holes through the bottom on the one side (NOT all the way through) Imagine them being an outlet for fuel to drain

[nickjaxe]

Ok got ya Morph thanks mate.

Nick.