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Gear set for Rotax 912 Engine

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4 weeks 1 day ago #20299 by mvigliassi
Gear set for Rotax 912 Engine was created by mvigliassi
Hello

I have a motor 912 with serial number 4152411 and I need to change the two gears set but there are three P/Ns
866125
866517
866518

What would be the P/N for my engine?

thank you

Marcos

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4 weeks 1 day ago - 4 weeks 1 day ago #20300 by admin
Replied by admin on topic Gear set for Rotax 912 Engine
4152411 was produced way back on 14-July-1993 and the factory has no record of the original gear set used. The one you choose depends on which gear ratio you want... most usual is 2.43:1 - but there are wide and narrow variants...
Last edit: 4 weeks 1 day ago by admin.
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4 weeks 1 day ago #20302 by mvigliassi
Replied by mvigliassi on topic Gear set for Rotax 912 Engine
Hello

Thanks for listening.

Would the 2.43 gear ratio below be compatible with my engine and could it be installed?

886517 GEAR SET I 2.43 narrow
886518 GEAR SET I 2.43 wide, 7 °

What would be the difference between narrow and wide options?

Best Regards

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4 weeks 1 day ago #20306 by RobSeaton
Replied by RobSeaton on topic Gear set for Rotax 912 Engine
The narrow 2.2727:1 is standard for the 912UL 81Hp.
You can install a narrow 2.43:1 p/n 886517. You will have to pitch your prop a little more as it will be going slower. You will have to be careful of detonation/overloading the engine (Use good fuel and stay above 5300 takeoff RPM).
No advantage to using the wide gears. Plus you would have to change the gearbox housing and the crankshaft.
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4 weeks 22 hours ago - 4 weeks 22 hours ago #20307 by mvigliassi
Replied by mvigliassi on topic Gear set for Rotax 912 Engine
OK, I understand that I can use reductions 2.27 or 2.43.

How can I know which gear is currently installed in my engine (narrow or wide) and the reduction?
Measurement, reference...

If I miss the purchase of narrow and wide it will not fit ...

Thanks!
Last edit: 4 weeks 22 hours ago by mvigliassi.

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3 weeks 6 days ago #20327 by Bill Hertzel
Replied by Bill Hertzel on topic Gear set for Rotax 912 Engine
What is the Gear Box Part Number? (Engraved on the Gear Housing)
8872xx and 996xxx are 2.27:1
8877xx and 888xxx are 2.43:1

The best way to guarantee what you have is to open it up and look at it.
Count the Teeth.
A 21 tooth gear driving a 51 tooth gear will give a 2.43:1 gear ratio. 51/21 = 2.43 ... and 50/22 = 2.27.

If it is a 912UL(80hp), it is almost certain to be a 2.27:1 Narrow
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3 weeks 5 days ago - 3 weeks 5 days ago #20330 by mvigliassi
Replied by mvigliassi on topic Gear set for Rotax 912 Engine
I opened the box and I have these attached photos. What is my gear box setting?
Is it possible to determine which of the three PNs below do I have to acquire?

886125 GEAR SET 2.27 narrow
886517 GEAR SET 2.43 narrow
886518 GEAR SET I 2.43 wide, 7 °

Thank you for your help!

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Last edit: 3 weeks 5 days ago by mvigliassi.

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3 weeks 5 days ago - 3 weeks 5 days ago #20331 by Bill Hertzel
Replied by Bill Hertzel on topic Gear set for Rotax 912 Engine
What was the part number on the gear case housing?

I count 50 teeth. 2.27 What did you get?
2.27 wasn't made in the wide variation.

You can confirm narrow by measuring the width of the gear.
22mm (Just under 1") = Narrow
27mm (Just Over 1") = Wide

All of this can be found in the Parts manual.

2.27 Narrow is still looking like the answer.
- - - - - -

Why do you think you need new gears?
Last edit: 3 weeks 5 days ago by Bill Hertzel.
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3 weeks 2 days ago #20366 by mvigliassi
Replied by mvigliassi on topic Gear set for Rotax 912 Engine
The TBO of the engine was made and the bearing of the reduction box was changed. After that the engine is attrition and is not spinning freely the propeller (I'm not sure if these are the correct English terms).

I thought the mechanic had changed the gears set and mounted it wrong, but I guess the problem was not that then.

I do not know where the problem might be. :(

Thank you for your help.

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