Carb Synch doesn't hold thru RPM range

Re: Carb Synch doesn't hold thru RPM range

by Rob Seaton » 13 years ago

Rob Seaton

3 1.32k 251

Its likely your cables: en-equal length? tiewraps binding one? Tight bend on one cable? Broken strand inside? Sticky? Swivel binding?
On our Europa it was not repairable; we need to replace the original cables with new, friction-free cables.

Re: Carb Synch doesn't hold thru RPM range

by MARK JACKSON » 13 years ago

MARK JACKSON

12 332 11

Hi Robert

That is what your balance tube is for.

You can only set the idle screw so the vacuum is equal at tick over, and any RPM on the cable adjusters. As you increase or decrease the revs, they will become out of balance.

Mark

Re: Carb Synch doesn't hold thru RPM range

by Roger Lee » 13 years ago

Roger Lee

131 5.38k 5.44k

Hi Robert,

It can be as Rob suggest, but this is exactly why I tell people to quit using the too low 2500 rpm to set up for the higher rpm sync. It is too close to the idle circuit rpm and doesnt flow enough fule and air to get things setup accurately for the higher rpm sync. Use 3500 + rpm. Then you won't have all the vacuum change as you throttle up. Read this:

http://www.rotax-owner.com/rotax-blog/item/16-the-anatomy-of-a-carb-sync

This should help.

---

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

Re: Carb Synch doesn't hold thru RPM range

by Robert Hirschfield » 13 years ago

Robert Hirschfield

2 16 0

Thank you for the replies. I am doing the procedure correctly, it has worked flawlessly in the past. I am going to take a very close look at my cables and go from there. Thanks again.

Re: Carb Synch doesn't hold thru RPM range

by MARK JACKSON » 13 years ago

MARK JACKSON

12 332 11

Robert

You should set your idle screws so that the vacuum is the same at around 1600-1800 rpm, then set the cable adjusters so the vacuum is the same at around 2500 rpm.

The vacuum should be "near enough" throughout the rev range, and any slight difference is compensated for by the balance tube.

Setting the cable adjusters at a higher rpm of around 3500 can mask underlying problems as to why the vacuum is not stable through the rev range and is not recommended by Rotax.

Mark