Carb Sync

Hi Larry,

I like to do my carby synchronisation at several rpm's.

I start at about 2500 go to 3000 - 4000 - 5000 rpm.

When I think I have got the synch as good as I can, I check from  about 2000 rpm, back up the speed range and down, pausing at each rpm to allow the engine to settle.

Low engine speed (high vacuum) will highlight any variation between the carby's.

High engine speed (low vacuum) will be hard to see variation BUT is where you want the carbys to be in best synch.

By moving the throttle slowly & pausing, up & down the speed range, you are also checking for throttle smooth operation (cable sticking or not).

Your carby balance tube will accomodate small variations in synch but still best to have synch as close as possible.

Be sure to secure (anchor) your aircraft before high rpm checks.

Hope this helps  😈

Most of us sync the high rpm at 3300 - 3500 rpm. This way the sync stays together as the throttle is increased. The 2500 is too low and too far into the idle circuit.

Hi Larry

The issue you describe, failure to maintain sync after initial settings,, suggests you are not doing the mechanical correctly first.  Please review the complete mechanical sequence first.  Once set, your linkage should then track uniform from just off idle to hitting the full power stops.  Complete this by doing the the phenmatice sync.  

Cheers

Hi RW,

Hope all is well.

No matter how I used to sync carbs syncing the higher rpm at only 2500 and then advancing the throttle always caused the gauge needles to separate again, but at 3300 - 3500 that never happens. I hear this from many many owners and mechanics. I still think the 2500 rpm sync for the higher rpm is too far into the idle circuit to represent a a higher rpm as the throttle is advanced. It has seemed to work for the last 20+ years. Carb syncs for me take about 15 minutes and I always make sure they are dead on.

It seems to work well.

It’s been my experience that carb sync will change with RPM. So I sync at cruise RPM where the motor spends most of its time.