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912is back to a 912

  • Malcolm Huddart
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3 months 2 weeks ago #14843 by Malcolm Huddart
Can a 912is be converted back to a 912 with proper carburretors & magneto's ?
Our 912is is becoming unreliable and difficult to maintain, it has now got to the
point where the downtime is affecting our operation.

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  • richard Boslaugh
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3 months 2 weeks ago #14846 by richard Boslaugh
What issues do you have with you 912iS. I have a 912iS with 200 hours and would be interested
in what problems could arise

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3 months 2 weeks ago #14847 by Glenn Martin
More info please.
It would be "possible" but I suspect the change back would be for more work than finding a qualified 912IS mechanic or someone whom wants to learn the new technology. I am sure the problems can be solved with the right people working on it. Where are you ? what resources do you have around you ? what are you trying to do that is different.

I "live" at a little field about as far from ROTAX as possible (south Island New Zealand) it has taken time for the support infrastructure to get their head around the new tech, if you are having trouble find a modern race car guy they know ECU's and fuel injection management very well it is their daily bread, perhaps they can help you ?

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  • Bill Hertzel
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3 months 2 weeks ago #14849 by Bill Hertzel
The simple answer is NO.
Converting back to carburetors is impractical and illogical.

The engine will tell you what is wrong with itself.

Do you have the BUDS software and "Dongle"?
They really are required and not optional.

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  • Malcolm Huddart
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1 month 2 weeks ago #15271 by Malcolm Huddart
It appears that 912iS goes through gearboxes whereas all the 912 don't suffer from this as much. We have had 3 gearboxes in 600 hrs. The symptoms are vibration which cracks Exhaust systems. There are approx. 17 Eurofox Glider Tugs on the UK Register only 5 of them including ours is a 912iS. Ours has the highest number of hours, there are Eleven 912 which don't seem to suffer the same gearbox problems.

There maybe some Operating techniques or Maintenance procedures that might help but Rotax are not giving us any help in this matter.

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  • Bill Hertzel
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1 month 1 week ago #15273 by Bill Hertzel
What engine are you referring to?
912 only designates an engine series. The 912 comes in the 912A, F, S, UL, ULS, and iS variations.
A 912UL is way different from a 912 ULS.

Gearbox issues usually point to excessive 'Moment of Enertia' in the Propeller. (Too Heavy of a Prop)
Excessive Moments of Enertia are hard on the gears and can damage the clutch quickly.
What Propellers are you using? Have they been Balanced?

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1 month 1 week ago #15286 by Glenn Martin
I think it must be your specific installation.
we have about 7 912IS engines in my local area and so far no gearbox issues. I would also look at the Prop, inertia, balancing, and any places that are non standard that could setup a harmonic. That is things like rubber isolators of incorrect shore hardness etc.

Check that you have a battery as large as specified in the 912 IS installation manual, it is bigger than a ULS one low voltage on starting is hard on gearboxes and sprag clutches.

Good luck

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  • geoffrey klestadt
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1 month 1 week ago #15293 by geoffrey klestadt
Malcolm, what fuel are you using? I am aware of a commercial user who has done 3 gearboxes - all on 100LL. There is a suggestion that the gear backlash settings on the 912 iS might be a little tight for regular Avgas use with lead buildup.

I don't think there is a general problem with gearboxes, otherwise it would be all over the internet.

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  • richard Boslaugh
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1 month 6 days ago - 1 month 6 days ago #15329 by richard Boslaugh
I have had my 912iS gear box rebuilt 3 times. Engine has 200hrs. total time. I have used 92 mogas all 200 hrs. I am inspecting oil filter every 25 hrs. as at the second rebuild enough metal was found to require the Rotax contaminated oil proceedure including new oil cooler. All rebuilds were rotax warranty.
Last Edit: 1 month 6 days ago by richard Boslaugh.

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3 weeks 6 days ago #15406 by Glenn Martin
I am sure you have it correct,

But can you confirm what UK 92 Mogas actually is ?

there are three common ways of measuring Octane, RON, MON and AKI (RON + MON/2).

In New Zealand the "pump gas" is displayed as RON.

92 RON is NOT high enough for a 912IS engine. The 912IS manual states a minimum of RON 95.

Therefore I need to use "95 octane" in NZ although the placards say minimum 92 as that is AKI not RON .

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  • richard Boslaugh
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3 weeks 5 days ago #15413 by richard Boslaugh
Hi Glen, Richard Boslaugh here. I am located in the US. The normal octane rating in the US is AKI. (average of RON and MON). So 90-94 AKI is equivalent to 95-99 RON. For those reading that have never heard of AKI it is the anti knock index of the particular blend. Also 92 Mogas has no ethanol added.
The following user(s) said Thank You: Glenn Martin

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3 weeks 5 days ago #15414 by Glenn Martin
Thanks...definitely not a fuel problem then,,

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  • geoffrey klestadt
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3 weeks 7 hours ago #15472 by geoffrey klestadt
Malcolm, what propeller are you using? Is it the same as the other injected rotax users? I believe 'Ive heard I knowledgeable Rotax person suggest that unsuitable propellers are often to blame for gearbox problems. its not just a moment of inertia issue, it can also involve blade vibration at certain rpm's.

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