Carb Float Bowl Breather/Overflow

""..........brass float armature ........."

Is this what Rotax Heavy Maintenance,73-00-10, page 13, calls "float brackets"

".....height 10.5mm......"

Yes, but the measurement depends on how you do it. If you use the Rotax tool that slides down over the main jet socket then you would use a feeler gauge with it to measure the gap and the measurement  number is different.

If you measure up from the carb outside bowl edge then it's 10.5mm to the flat top part of the float armature. I just use a MM ruler. I've done hundreds of carbs with no issues.

Roger,

FYI - From another Forum.

A potential contributor, to small leaks from the carburettor bowl breather, is temperature.

Should the fuel in the float bowl boil (get bubbles in it) the floats will sink, reducing their ability to regulate incoming fuel - overflow!

I have been struggling with cowling air flow - it is possible (seems unlikely) that under cowl temperature are getting sufficiently high to cause the fuel to boil.

If this is happening it is likely to be during climb out and be of short duration - I will try and monitor cowl air temps more closely.

"A potential contributor, to small leaks from the carburetor bowl breather, is temperature.".

Possible, but I think fairly rare. Everything would have to be hot and another contributor is no heat shield between the bowls and the exhaust pipes.

There are a lot of engines and it seems fairly rare to hear about something like this.

But who knows you may have the answer to your leak.

Well the replacement of the air filter, with a brand new (clean) one, may have resulted in a small reduction (wishful thinking?) in fuel collected in my breather catch cans.

The only remaining option, is to remove the carburettors and check/adjust if necessary the brass float armature/float brackets for correct position.

I have been reluctant to go down this path because, the amount of fuel collected in minimal - less than 100mm/4hrs. The engine start, runs & performs with Rotax excellence, my Sonex is parked in what is basically a grassy field, not conducive to doing much mechanical disassembly/assembly. Its a tedious job involving much cutting of zip/cable ties AND disconnecting the liquid carby heating/anti ice system and, in Australia, contending with the unwelcome attention of flies.

Oh well! needs must - will wait for auspicious weather conditions (not today, its going to be 40+C)

Just an update from my float bowl issue after re-installing my carburetors.  I never found what was preventing the one float needle from seating properly.  But after removing and re-insatlling that bowl and floats, as previously reported, all has worked well.  I've done the carb sync and throttle re-calibration, which was still within tolerances from before removing the carbs.  I would still like it to run smoother so I may try another sync.  Perhaps I'm just being too much of a perfectionist.  One question though since the MMH does not say to peen the throttle valve screws.  (I know the video does, but I didn't see that until too late.)  Will the Loctite 603 and "good" torque to the screws hold them in place for awhile, perhaps at least another 200 hours?