912 fires 4 to 5 times before complete stop

by miguel acosta in 912 / 914 Technical Questions 13 years ago

Hi,

My 912 UL serial/4.404.781 fires 4 to 5 times before a complete stop
when igniton switch is turned off. IT started to do so last 7 shut downs.

It runs smoothly from idle 1800 rmp all the way to full power to 5600
CHT is ok below 120 Celcius
Fresh air is ok on the Carb intake
I just changed Spark plugs it is using as indicated on the manual: DCPR 7E
Im using a non in flight variable pitch warp drive three blade propeler.
Carburatos service done 20 hours ago.

Any one has experienced this problem any idea to solve it?

Re: 912 fires 4 to 5 times before complete stop

by Roger Lee » 13 years ago

Roger Lee

126 5.14k 4.62k

Hi Miguel,

How many hrs on the engine? I doubt this engine has one, but did you have the slipper clutch installed in the gearbox?
The big question for me is, what size Warp Drive prop are you turning and does it have nickeled edges? If you tell me it is over 68" with nickel edges I would say you need a smaller diameter Warp because the solid Warp Drive prop is heavier than the composite props and having the nickel edge is a double whammy. It will cause pre-mature or excessive wear whether anyone wants to admit it or not. When was the last time you synced the carbs? Another question is what fuel are you using?

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

Thank you said by: miguel acosta

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Re: 912 fires 4 to 5 times before complete stop

by Mike Brown » 13 years ago

Mike Brown

0 39 11

On older 912s the kill switch (mag switch) wires from the Ducati ignition modules have no provision for strain relief and can break. The break in the copper conductor occurs inside the plastic insulation and so the break is not visible. When this happens the engine will not shut down as the kill switch(es) can no longer ground the ignition module(s) through the broken wire(s).

The kill switch wires have flesh-colored plastic insulation and will typically break within one to two inches of the ignition modules. You can check these wires by carefully holding them in both hands and pulling gently on the wire. It will be obvious if there is an internal break in the copper conductor as the plastic insulation will stretch with very little resistance at the location of the broken copper conductor. The fix is to repair the broken wire with a crimp connector or with a soldered repair and then to properly strain relieve the wire.

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Re: 912 fires 4 to 5 times before complete stop

by miguel acosta » 13 years ago

miguel acosta

1 1 0

Hello Mike ,

I thank you for your response. I went yesterday to the airfield and found a false conctact on one of the kill cables. I repair it and now is working fine. Your help was so valuable. Thanks a lot. That wolud had been the last thing I would figured out. Happy flying. ! :)

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Re: 912 fires 4 to 5 times before complete stop

by Mike Brown » 13 years ago

Mike Brown

0 39 11

Miguel:

My pleasure. I'm happy to have been able to help.

Mike

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912 fires 4 to 5 times before complete stop

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