Carburetor sync at 100hr

I start with checking the balance, if it is off typically all that is required is a small adjust on one of the Bowden adjusters. To determine which one decide which one will bring the idle closer to the RPM you desire. 

Just do the pneumatic synchronisation - its so easy/quick to do and it's quite possible that no adjustment will be required but if it is, then you will have maintained your engines efficiency & prolonged its service life.

I’ve been doing the pneumatic every 100 hours. I balance at cruising rpm because that’s where most of the operating is and the balance seems to change at different rpm’s.

Sam Purpura wrote:

I’ve been doing the pneumatic every 100 hours. I balance at cruising rpm because that’s where most of the operating is and the balance seems to change at different rpm’s.

I  "balance"  in the range 2500 - 4000 rpm. 

Like you, I find changes over the range but work on the assumption that the greatest vacuum is in the lower rpm and it is here that differences will be most marked and have the greatest impact (on smooth idle). I am obsessive about getting the balance just right at this rpm.

Get your low rpm right and differences up the range will be small.

The balance tube will, to some extent, accommodate small differences in balance that are probably due to throttle (Bowden) cable movement/binding ie not always delivering exactly the same movement on both sides for each actuation.

I have a "winge" about the Rotax throttle cable adjustment mechanism - it is unnecessarily fiddley - the screw mechanism (length of outer sleeve) should be into a threaded "fixed" point, with a single locking nut. With a single spanner (8mm?) the single lock nut can be loosened, the adjuster turned by finger pressure and the lock nut applied to secure in position.