mag test low rpm

by Awod Alahmari in 912 / 914 Technical Questions 13 years ago

hello every body
i have rotax 912 uls and when i do the mag test at 3800 rpm it should drop only 150 rpm but mine drops 700 rpm on each side #1 or#2.

i replaced the spark plugs and cleaned the filters and it did the same.
so where can i start my tests. :blink:
best regards

Re: mag test low rpm

by Conrad Beale » 13 years ago

Conrad Beale

3 66 22

A drop of this magnitude indicates the loss of one cylinder on each mag. I would guess you have two plug caps incorrectly connected.
The 912ULS enggine has the ignitions connected as:
Circuit A - 1,2 Top 3,4 Bottom.
Circuit B - 1,2 Bottom 3,4 Top

If you have accidently connected the plug caps incorrectly (for example cylinders 1,3 bottom, which are on the same side of the engine) you will get about 600RPM drop on both mags.

Please note this applies the same to the 80Hp engine , but not the 115Hp(914) engine as it has the mags connected differently.

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Re: mag test low rpm

by Roger Lee » 13 years ago

Roger Lee

128 5.28k 4.98k

I agree with Conrad. You have some wire swapped some where.

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

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Re: mag test low rpm

by Awod Alahmari » 13 years ago

Awod Alahmari

10 31 66

THANK YOU VERY MUCH MY FRIND
I WILL CHECK THE WIRES AND LET YOU KNOW .
THANKS FOR THE REPLAY I DEED.

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Re: mag test low rpm

by Awod Alahmari » 13 years ago

Awod Alahmari

10 31 66

Hi Conrad Beale
how are you doing ?
today i went to my plane and looked at the spark plug wires and i found a seally :blush: :oops: thing causes the proplems.
# 3 & 4 wires are swaped i reverced them as it shows on the intake maufuld and i did a n engine run and did the mag test it was pevect only drops 100 rpm in each switch :woohoo: .

i really apreteate all your help from all of you .

best wishes and merry crismes.

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mag test low rpm

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