912ULS Soft Start

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

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Re: 912ULS Soft Start

by William Taylor » 7 years ago

William Taylor

0 4 0

I have a photo of the electronic ignition control module(s) and you can see the part number and the yellow tagging on the top module. The part number is 966727, there is another number embossed on the side of the top module, 10.0425, and the yellow tape on top of the module is marked in black 10.0505. The lower module has the same 966727 number embossed on the side, but 10.1028. Does any of that mean anything to you?

If I could figure out how to attach it, I would send the photo.

Bill Taylor

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Re: 912ULS Soft Start

by William Taylor » 7 years ago

William Taylor

0 4 0

I can't say the engine runs rough for a few seconds on start up, but candidly, haven't given that much thought. When I next go to the hangar I'll crank it up and advise.

We have probably eight-nine foot long fairly small gauge wires from the battery to the starter. I'll measure their gauge when at the hangar next time and advise. Maybe we have a voltage drop from battery to starter that is reducing the starters efficiency.

Bill Taylor

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Re: 912ULS Soft Start

by Roger Lee » 7 years ago

Roger Lee

126 5.14k 4.58k

The longer the wire from the battery to starter the bigger the gage needs to be. If you're really 8-9' away then that wire should be fairly large.

Just a thought,
Is this a brand new engine or does it have some time on it? If it has some time on it and this is a new problem then it isn't likely the wires.

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

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Re: 912ULS Soft Start

by Jerry B » 7 years ago

Jerry B

1 7 0

Kick back has always been a ignition module problem specially on 912uls because of the higher compression. Not battery or wire length . That's why it has now been sorted with new ignition module and flywheel.
The flywheel produces two pulses as it passes the pick up. The first is to run normally, second for starting. When you crank the engine you are well below engine running speed and the module should ignore the first pulse and fire on the second, just before TDC (old flywheel).
Problem is some modules fire on first pulses when cranking, 26BTDC which causes the kick back. Yes you can have a stronger battery/starter motor to try and turn the engine faster through commpression, but if module fires on first pulse, you will get kick back, then sprag clutch problems start.

Using 2 switches for the ignition I could crank my engine, then turn A and B ignition on. I only got kick back when both were turned on or the A module was used first with no problems using B module first.

Yes I then swapped A and B to eliminate pickups and HT leads. Problem stayed with the module.

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Re: 912ULS Soft Start

by Roger Lee » 7 years ago

Roger Lee

126 5.14k 4.58k

You should NEVER have kickback on a start sequence or you WILL damage the sprag in the starter. If you have kickback at start you should stop the flying until you solve the issue. There are some simple solutions to stop kickback.

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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