What’s your 912iS idle rpm set to?

Howdy Rotax Wizard,

Hope all is well. It's  been a while.

One thing I have gotten away from are heat guns. They heat or may damage everything in the area and no pin point heat. Now I use a small butane torch that I can pin point my heat and do a better job of heat control and it keeps it from possibly damaging things in the adjacent vicinity. So far so good and no issues. Heat at times really helps break stubborn screws or bolts lose so you don't  damage things.

The Operators Manual Lists a Minimum of 1400 rpm.
Most people set it a little bit higher.
I set mine to 1700-1800 Hot.
It could be lowered a bit as taxi speeds approach 20kts without using the brakes intermittently.

The Idle Screw can be adjusted without any drama.
It just has a splash of Touque Seal / Inspection Lacquer on it. (I just Looked.)
It turns easily with a screwdriver with only mild resistance,
Just enough friction to keep it from drifting in operation.

Once you are happy with it, paint it up again.

I've  seen a couple people break the idle screw on the 912iS by trying to use muscle to turn them. Add some heat and it turns easily. I'm  like many and prefer an idle rpm closer to the 1700+ mark. I think Rotax programed us from all the years prior. LOL We didn't change. ? I'm  not sure if that's  good or bad. ?

This is one area and reason I now prefer a small pencil tip butane torch. I can be very accurate where I apply heat and not over heat items in the surrounding area or I can apply heat around a bolt and not heat the bolt and all surrounding items. Just more accurate and controlled vs a heat all heat gun.

Rotax Wizard wrote:

hi Roger...yes you can but I hate heating that area of the throttle body.  The temperature required to soften Loctite is about 400 F, it worries me at that level and where you have to heat.  For the past 10 years since the iS was introduced all the ones I have seen broken were on OEM adjusting the idle screw to meet what they believed was correct speed.  In the iS is is much less of an issue and given you must run the engine almost immediately to 2500 to switch on the A side of the computer it is much less of a problem.  The iS tends to idle much better since fuel is relatively lean compared to the carb version engines.  

The newest throttle bodys used, starting a few years ago, now have an additional screw to set idle independent of the one that was always there.

I need to be clear, Rotax has 2 versions of the throttle bodys used.  The original had only one screw.  This is fixed with Loctite and set to min idle speed by the factory.  This one is not replaceable and was not intended to be changed.  

Later versions have a second screw, if this is what you have then go at it and adjust away as that is exactly what it is for.  The dual screw version part number is shown in the 915 iPC along with the old version with the single screw.  The 055 was single screw and the 056 is the newer one with the second, adjustable, idle screw.

I hope that helps.

Cheers

See attached for reference. 

Rotax Wizard, quick non sequitur: Why do Rotax manuals say "2500" to switch on the A generator? At least on my 912iS, it's actually 2400. My POH says 2600, Rotax operating manual says 2500, but it actually does the switch after just a few seconds at 2400.

Bill Hertzel wrote:

The Operators Manual Lists a Minimum of 1400 rpm.
Most people set it a little bit higher.
I set mine to 1700-1800 Hot.
It could be lowered a bit as taxi speeds approach 20kts without using the brakes intermittently.

The Idle Screw can be adjusted without any drama.
It just has a splash of Touque Seal / Inspection Lacquer on it. (I just Looked.)
It turns easily with a screwdriver with only mild resistance,
Just enough friction to keep it from drifting in operation.

Once you are happy with it, paint it up again.

Thanks, Bill. My current minimum idle when warm is 1480 (when cold about 1380). Do you recall how many clockwise turns you gave the idle screw to bring it up to your current 1700-1800 warm? Where is the idle screw located on the 912iS? 

And do you taxi at 1700rpm? I thought 1800rpm is the minimum you want to do extended idle for, and really 2000-2200rpm ground idling is most ideal?