Rotax A drive, Rotax A gear box, Rotax A reduction drive and gear box parts.

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Rotax A gear box parts

Rotax A provision 4 reduction drive parts and prices.

Rotax A provision 4 reduction drive parts

# Part # Description Qty Req.
Rotax A gear box
1 850 430 O-ring  1
2 910 505 Adapter 1
3 841 901 Stud 8 x 91 2
4 841 911 Stud 8 x 103 2
5 841 940 Allen Screw for 532 4
  841 820 Allen Screw for 377/447/503 4
6 850 360 O ring 1
7 910 911 Gear housing 1
8 932 091 Ball bearing 1
9 841 881 Stud 8 x 75 2
10 929 670 Dowel 10x13  2
11 930 532 Gasket  1
12 886 200 Gear set, 2.58:1  1
  886 202 Gear set, 2.24:1  1
  886 204 Gear set, 2.00:1 1
13 827 785 Washer 1
14 945 766 Lock washer VHV 13  1
15 841 656 Hex screw (60NM) 1
16 910 371 Gear cover 1
17 850 055 Oil seal 1
18 837 029 Prop shaft 1
19 827 850 Distance ring 1
20 932 820 Ball bearing  1
21 445 070 Snap ring 62x2  1
22 944 470 Shim 25.5/34/.2 As Req.
  944 471 Shim 25.5/34/.3 As Req.
  944 472 Shim 25.5/34/.5 As Req.
  944 473 Shim 25.5/34/1 As Req.
  944 474 Shim 25.5/34/.1 As Req.
23 847 620 Distance 3 ring  1
24 939 020 Disk spring 850  12
25 958 770 Dog hub  1
27 944 469 Thrust washer  2
28 827 840 Angular ring 1
29 827 860 Ring half  2
30 945 752 Lock washer 6
31 242 201 Nut 8 mm 6
32 552 280 Gasket ring 1
33 840 270 Magnetic plug 1
34 830 890 Gasket ring 2
35 841 781 Capstan screw M6x10  2
36 941 115 Air vent screw 1
38 SW032 Safety wire  As Req.
39 827 830 Cover washer 1
34 LT222 Loctite 222, violet As Req.
35 LT680 Loctite 680, green As Req.
36 PSAS Anti-seize  As Req.
37- 8P Energrease As Req.

Rotax A gear box installation.

1. Clean and degrease the crankshaft end and mounting holes on the crankcase before starting.

2. Using the Rotax fixation tool supplied in the Rotax tool kit lock the engine up by installing the pin into the impulse hole, used to run the fuel pump. With the pin in place rotate the engine, until it locks.

3. Install drive gear onto crankshaft end, with the lockwasher under the head of the bolt, and the flat washer under the lockwasher. Torque to 45 FOOT lbs.

4. Install the rubber O ring (#3) into the back half of the gearbox adapter plate, if necessary use dielectric grease to hold ring in place.

5. Position back half of gearbox (#1) onto crankcase. Apply loctite #242 to threads of bolts (#4) install 4 allen bolts bolts and torque 30 FOOT lbs.

6. Install the rubber O ring (#3) into the front half of the gearbox adapter plate, if necessary use dielectric grease to hold ring in place.

7. Install back half of gear box housing.

8.Install gasket - make sure gasket is not damaged.

9. Install front half of gear box housing and secure with bolts/nuts and lockwashers. Use loctite 242 on threads and torque to 195 INCH lbs.

10. Fill gear box with 90 weight oil until oil runs out the lower of the two side plugs.

11. Tighten then safety wire top and bottom plugs.

12. Tighten then safety wire vent cap and drain plug.

Rotax A Gear box updates:

Updated - Rotax gear, dog hub, washers, shaft.

Aircraft: All ultralight aircraft using the Rotax reduction drive.

Incident report:

We have several reported problems from pilots using the Rotax reduction drive.

1. a hard to start engine, or an engine that will start but has a hard time coming off an idle or runs very erratic at idle.

2. the gears inside the gear box disintegrating, especially on engines using large radius propellers.

3. the gear box retaining bolts vibrating loose and or breaking allowing the gear box to in one case come right off the back of the engine.

4. the output shafts on the gear box especially on the 65 hp engines, severing, or the prop shaft hub cracking.

5. the oil slinger located on the end of the output shaft breaking and then getting messed into the gears.

6. the loss of reduction drive gear oil during flight.

7. the stripping of the bolts used to attach the prop to the hub of the gear drive.


1. There was a problem on early Rotax gear drives where a series of spring washers inside the gear box, over a period of time lost their tension.

This in turn caused the engine to become hard to start, and would not come off an idle. Rotax has an update kit which replaces the eight spring washes, and spacers found in the old style gear drives with a new 12 spring washer system. 

It is recommended that these spring washers be replaced every 150 to 200 hours and that the gear drive oil be checked periodically, and replaced every 100 hours or yearly which ever comes first.

2. The problem with the gears shattering was also an early problem, and there is also a retrofit kit, which replaces the gear with a stronger gear.

3. The problem with the retaining bolts backing off was more common on the 3 bolt pattern adapter plates, the new engines are 4 bolt. This problem was also caused by pilots who were reinstalling the gear box for whatever reason. 

In reinstalling the bolts on the 3 bolt system, there are two different lengths of bolts. Both bolts will go in and appear to tighten the plate against the housings. In fact the longer bolt is bottoming out in the crankcase housing and is NOT tightening up on the adapter plate.

4. The aluminum hub cracking hub cracking problem were also corrected on later model Rotax reduction drives, I am not however aware of a retrofit kit for this at this time. The only suggestion would be to update to the new style steel output shaft and hub.

5. The oil slinger problem has been eliminated by the removal of the slinger completely. New model engines do not come with the oil slinger, and the removal of them is recommended on older style gear drives.

6. The stripping of the prop bolts seems to occur when pilots have taken off and reinstalled their props several times. Some pilot have reported drilling out the holds using larger bolts, with locking nuts, and safety wire.

Other pilots have simply gone to larger bolts and used the other bolt pattern on the redrive. This problem is caused by the pilot over torquing the prop bolts on installation. The recommended torque is 100 INCH LBS.

7. The gear oil existing problem can be cured simply by installing a very small gas line filter on the top of the reduction drive vent cap using a small piece of gas line and some clamps. It is caused by the prop creating a low pressure area above the vent, siphoning the oil out of the gear drive.

Rotax Engine Rebuilding Videos
Rotax engine rebuilding videos, each video is approximately 2 hours in length and takes you step by step through the tear down, clearing, and reassembly of a Rotax engine

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Updated gear, dog hub, spring washers, and shaft.


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