912ULS Soft Start

by Gary Taylor in 912 / 914 Technical Questions 8 years ago

Hi Guys,

Could anyone tell me if all new 912ULS with slipper Clutches, have a soft start kit installed within its ignition, or is this something you add at a latter date

GT

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Re: 912ULS Soft Start

by Roger Lee » 8 years ago

Roger Lee

126 5.14k 4.58k

Hi Gary,

The newer 912ULS does have the setup for soft start. You do need to connect two wires from the ignition modules to the starter solenoid, but that's all. The soft start is mainly the newer ignition modules and a newer style flywheel.

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

Thank you said by: Gary Taylor

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Re: 912ULS Soft Start

by William Taylor » 7 years ago

William Taylor

0 4 0

Our Zlin Savage has a 2010 model 912 ULS and is prone to kickback on starts. I've seen some posts on a soft start module that changes the timing during the start sequence. Where can I learn more about the model and perhaps acquire one?

Bill Taylor

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Re: 912ULS Soft Start

by Roger Lee » 7 years ago

Roger Lee

126 5.14k 4.58k

Hi Bill,

You need to stop starting the engine until those kickbacks are stopped or you will ruin the sprag and then you'll have to tear down the back end of the engine and replace it.
here is a couple most common causes;

Weak battery. This can easily be checked by either replacing a battery with a good one or by just jumping the existing battery to make sure it has good voltage at start. Many have claimed they thought they had a good battery when it wasn't. This needs to be ruled in or out.

Poor carb sync and it may be in conjunction with improper spark plug gaps. (.023 to .027) The colder the climate the narrower the gap.

Old spark plugs

Improper start up technique. Do you use a primer system or the standard choke system? If it is a primer system get rid of it and install a choke setup.

Old black painted starter. The gold colored one is a higher torque starter

These are the most common. Rule each in or out as a player in your problem.

Rule out the battery, plugs and starter first because you'll need to run the engine for a carb sync.

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

Thank you said by: Awod Alahmari

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Re: 912ULS Soft Start

by William Taylor » 7 years ago

William Taylor

0 4 0

Thanks for your quick response.

We learned about weak batteries last spring. We had a three year old battery, it would spin the engine but not start it. We learned it had to spin the engine faster than 240 rpms (maybe faster?) to get the mags to spark. We replaced the batter and solved that problem.

The carbs were synced by a qualified Rotax mechanic last fall as part of regular maintenance, plugs replaced at the same time, gapped at 25.

We have the conventional choke system and use it when the weather is cold. In the summer the engine starts with the throttle closed and perhaps half choke on cooler days, with slight throttle and no choke on warmer days.

Maybe I am overstating the kickback issue. If you crank the engine to start it and it fires but doesn't start, the prop kicks back an eighth turn or so. Usually it only occurs the first time the engine is run for the day, and then only maybe one in ten starts. When the engine has been run that day, or when the engine is warm, it starts smoothly and quickly.

The engine is on a Zlin Savage on floats, so it only flies in the spring, summer and fall. The other five-six months our Minnesota lake is frozen.

I recently read about the soft start module and thought installing it might help with the occasional kickback.

Maybe we already have it….a local home builder who professes to know about Rotax engines said that if the labeling on the black electronic ignition box was yellow, the soft start feature was built in. Is that accurate? If there is a way can identify whether the engine has the soft start feature I would like to know it. Assuming it does not, I would appreciate any advice on whether adding it would be useful to “soften” the occasional kick-back, and where we can get the module.

Bill Taylor

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Re: 912ULS Soft Start

by Roger Lee » 7 years ago

Roger Lee

126 5.14k 4.58k

If you have the yellow lables on your ignition modules you already have soft start, but maybe they aren't hooked up. When then engine starts does it run a little rough time for about 6 seconds and then run smooth all of a sudden? If your engine is new enough to have soft start it also has the better starter.
If you dont have the soft start the answer is yes it will help.

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

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912ULS Soft Start

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