912UL Carb sync

I made a 1" crossover tube for my 912ULS, It definately helps but you should still balance the carbs. I made adapters to fit into the couplers that the carb balancer fits into.

pics here http://waltsrv12.com/engine/1-inch-balance-tube/

Nice. Thats basically exactly what is installed on my engine except mine is a heavy duty rubber hose all the way across. I just need to make some adaptors to fit on my 1" connectors on the intakes & get the carbs balanced properly. 

Thanks 

Wow!  that's one hunk of hose. 

"The guy who did it claims that it smooths out the low end.

I have heard of this modification before however have yet to understand how its installation benefits the engine .

The balance tube is there to even out any difference between the two inlet manifold vacuums. By doing this it helps to achieve equal fuel air mixtures to each side of the engine and thus smoother power delivery. Making it larger is unlikely to have any significant benefits in this regard.

As for "low end" improvements - since when was a Rotax 9 in flight, operated at low rpm?

Can the carbs be synced without a prop on the engine? 

hi all

First for Jesse, yes the prop is a required load.  It acts as a flywheel and also a governor, without load carb sync is a waste of time.  You must have the engine at operating temperatures and with the load set as near correct as possible.

Second, for the speculation of the extra large compensation tubes.  This black magic has been circulating for years.  Indeed it may feel nice at idle however that is not the job of a carb sync.  We need to get the engine to run correctly when it is developing power.  The primary intake manifolds must be short to make the required power at peak.  Oversizing the compensation tube has no effect on more HP.  We have to isolate each bank when we do a carb sync so I think it is a red herring, a distraction, to bring up in this discussion.  

Cheers