balance tube

Re: balance tube

by Mike Goodrich » 9 years ago

Mike Goodrich

8 123 0

Roger
See my post 7319 from 2 years ago, we're singing from the same song sheet.

Mike

Re: balance tube

by Matthew Dock » 9 years ago

Matthew Dock

0 3 0

I think Rotax used that diameter tube because it probably works ok at cruise RPM. However, looking at the vibration spectra of the engine in the mid range, it is obvious the engine is having breathing issues due to the difference in the front and rear cylinder's manifold lengths. You can usually see this in the plugs if you run in the mid range. I'm curious what the plugs look like after the engine has run for a period of time in the mid range RPM; to see if they look the same.

Also, if anyone has a DynaVibe GX2 that has done the balance tube mod, I'd like to work with them to get a vibe spectra off the engine. My guess is that the specific vibration we see on all the 912s at the mid range RPM will be much smoother.

Matt

Re: balance tube

by Michael Sweeley » 9 years ago

Michael Sweeley

8 25 0

Since I have limited facilities I opted to install the “Flygas” balance tube assembly. I am extremely pleased; the engine is much smoother at lower idle speeds. Fuel consumption appears down while cruising at 5000 RPM. Big thing seems to be that there is no need to continually balance the carbs. I requested that Flygas provide me with fittings that fit over the carbs when I do want to balance them. It is quite simple now to do so…simply remove the crossover pipe from the rubber attachment at the top carb intake and slip in the machined fitting with 1/8 inch fittings to which you attach the ¼ inch tubes to the manifold balance instrument. Very easy! One problem arose with the Flygas manifold…one fit perfectly the other needed to have the bolt holes drilled out a bit apparently bad casting) but really no big deal. For those of you who do not want to do a lot of modification work to fabricate these tubes I do recommend Flygas.
Regards
Mike
PS: the one concern I had was whether the new Flygas tube would fit under the tight cowling of my Aeropro…no problem plenty of room.

Re: balance tube

by Garrett Wysocki » 9 years ago

Garrett Wysocki

1 572 1.45k

Thanks for the feedback.

Re: balance tube

by Roger Lee » 9 years ago

Roger Lee

131 5.38k 5.44k

The stock balance tube is only good up to 3500 rpm. After that it is ineffective.

---

Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell