Carb sync? Never again.

[kitfox2009]

Update.
Well today just for fun I made up a larger balance tube for my 912Ul.
Material required is a 14 inch length of 1 inch heater hose plus two 1inch pieces of 3/4 inch and 2 approx 3 inch pieces of 1/2 inch. 4 hose clamps and 1 Mini hose nipple if you have a manifold pressure gauge.
Assemble as shown. I used the adhesive in the photo.
Have not flown yet but runs smoothly through all RPM ranges on the ground test. I realize this only increases the balance tube to 1inch diameter but might be interesting results. Ran smoothly before but maybe even better now!

Cheers
Don

[Rodney]

That looks great. Seems like one inch or greater does the job. Sure is nice to sit on the ramp with the idle set at 1200 to 1400 with no shake rattle n roll.

Rodney

[kitfox2009]

Hi Rodney
Just did a 2 hour low level site seeing trip around our "smoky" valley this morning. With all the fires this year our area is nick named "Smokanagan" now.
Anyway I have a feeling that the new low budget carb balance tube provides a smoother operation through all RPM ranges. Quite impressed. It`s so easy to make up and the cost is zero.
Have fun
Don

[efwd]

Hmm, why do I hear so much about trusting the engineers? Why did they not go with a one inch diameter or why have they not gone back and changed the equipment yet?

[kitfox2009]

Guess this is why USA calls our a/c type "Experimental and we Canadians call them "Homebuilt". Nice,EH!!

Have fun
Don

[Rodney]

Efwd. As Travis Tritt said in one of his songs. "It's all about the money."

Also, seriously, just because they built it, don't assume they know everything.

Too, I've been in meetings where a "junior" engineer proposed a perfectly good inexpensive solution to a problem, only to have the idea rejected by some manager who thought he knew everything.

Could be lots of reasons they didn't put one on.

Rodney

[kitfox2009]

G'morning Rodney
I believe the title to this thread is a bit misleading. I strongly believe we should all sync the carbs on a regular basis BUT unless you are able to keep "the green light in the middle" through all RPMs from idle to full throttle (It was always a compromise for me) then maybe a modification to the balance tube might be helpful.
Going to a breakfast flyin this morning. We'll see how another 2 hours air time goes.
Take care
Don

[Wheels]

I'm pretty impressed with what you guys are seeing. I imagine a cracked tube or broken seal would act like a carb boot failure. Am I right? Just wondering what the failure chain looks like before we go there. I don't see any extra links in it from the old aluminum and rubber hose assembly that came with the engine.

[Pilotharry]

Fellow Flyers,
I finally did the enlarged balance tube mod on my 912UL over the last couple weeks and have flown for about 2 hours now and can firmly confirm that:
-It runs very smooth over the full throttle range
-No change in my performance numbers except that it feels lot smoother overall. (it feels more powerful)
-Cold start is like a car with no shudder or vibration.

Not enough time to say if it changed my fuel consumption but I would assume it will run more efficient just because of all that smoothness and both banks running hand in hand.

I will remember to take some pictures next time but all I did is that I drilled and taped the existing balance tube holes to 3/8"NPT and screwed in the 3/8" 45 degree male to female fittings in them. I drilled out the fittings ID to remove any casting imperfections and increase the ID a bit.Then I took a 3" long 3/8" NPT nipple and cut it in 2 halves. Screwed each half into the fittings added. Connected both sides with a 9/16" Vacuum hose from PartSource. All fittings were thread locked on final assembly.
Feel free to contact me with any questions and I will consider doing all the machining and supply parts as kit for anyone who would like to give it a try for something around $300.

Happy Skies,
Harry

[DesertFox4]

Thanks Harry. I have recently talked to a couple Rotax powered Kitfox owners looking into this modification.