Mantis Tiller 7940 2017 Upper Worm Shaft Roller Bearing Replacement Repair Guide

Difficulty

Moderate

Steps

Time Required

                          40 minutes - 1 hour

Sections

Mantis Tiller 7940 (2017) Spark Plug Disconnection
4 steps
Worm Gear
13 steps
Lower Worm Shaft Roller Bearing
8 steps
Worm Shaft
1 step
Upper Worm Shaft Roller Bearing
5 steps

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Introduction

For this guide, you will need to use a hammer to tap out certain components that are friction fit into place. In order to do this, you will need to find a way to brace the tiller in place so it doesn’t move around during the process. You can use a vice, or have someone else brace the part while you use the hammer.

You will need replacement lithium grease for this repair.

What you need

Step 1

              Turn off the ignition switch

Before starting any repair, ensure the ignition switch is in the “off” position, as shown.

Before starting any repair, ensure the ignition switch is in the “off” position, as shown.

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Step 2

              Remove the spark plug housing

Use a 4 mm hex wrench to remove the bolt securing the spark plug housing.
Throughout this repair, keep track of each screw and make sure it goes back exactly where it came from.

Use a 4 mm hex wrench to remove the bolt securing the spark plug housing.

Throughout this repair, keep track of each screw and make sure it goes back exactly where it came from.

Step 3

Remove the spark plug housing from the engine.

Remove the spark plug housing from the engine.

Step 4

              Disconnect the spark plug

Grab the rubber housing at the end of the spark plug wire.
Pull firmly to disconnect the wire from the spark plug.

Grab the rubber housing at the end of the spark plug wire.

Pull firmly to disconnect the wire from the spark plug.

Step 5

              Unfasten the upper handle assembly

Twist and remove the knobs and acorn nuts from either side of the handle assembly.

Twist and remove the knobs and acorn nuts from either side of the handle assembly.

Step 6

              Set aside the upper handle assembly

Remove the upper handle assembly from the lower handle assembly.
Do not pull the upper handle assembly too far from the rest of the tiller as it is still connected to the engine via the throttle cable.
Un-clip the throttle cable from the cable clips on either side of the handle assembly and set the upper handle assembly aside.

Remove the upper handle assembly from the lower handle assembly.

Do not pull the upper handle assembly too far from the rest of the tiller as it is still connected to the engine via the throttle cable.

Un-clip the throttle cable from the cable clips on either side of the handle assembly and set the upper handle assembly aside.

Step 7

              Remove the tine assemblies

Slide off and remove the tine retaining pin from the outer face of each tine assembly.
Caution: Take care when handling the sharp tines to prevent injuring yourself. Wear work gloves if necessary.
The tine assemblies can slide freely once their respective retention pins are removed. Do not let the assemblies fall off the tine shaft as this may damage them or result in injury.

Slide off and remove the tine retaining pin from the outer face of each tine assembly.

Caution: Take care when handling the sharp tines to prevent injuring yourself. Wear work gloves if necessary.

The tine assemblies can slide freely once their respective retention pins are removed. Do not let the assemblies fall off the tine shaft as this may damage them or result in injury.

Step 8

Slide off and remove both tine assemblies from the tine shaft.

Slide off and remove both tine assemblies from the tine shaft.

Step 9

              Remove the gear housing cover

Use a Phillips #2 screwdriver to remove the four screws securing the gear housing cover.

Use a Phillips #2 screwdriver to remove the four screws securing the gear housing cover.

Step 10

Remove the gear housing cover.

Remove the gear housing cover.

Step 11

              Remove the worm housing gasket

Remove the gear housing cover gasket.
We suggest you replace this gasket during reassembly every time you open the worm gear housing to prevent any grease from leaking from the worm drive.
During reassembly, refill the worm gear housing with an adequate amount of lithium grease before installing the gasket and housing cover to ensure smooth operation of the worm drive.

Remove the gear housing cover gasket.

We suggest you replace this gasket during reassembly every time you open the worm gear housing to prevent any grease from leaking from the worm drive.

During reassembly, refill the worm gear housing with an adequate amount of lithium grease before installing the gasket and housing cover to ensure smooth operation of the worm drive.

Step 12

              Remove the tine shaft

Use an adjustable wrench to turn the right half (in the orientation pictured) of the tine shaft clockwise, as shown.
Continue to turn the shaft clockwise until it is unthreaded from the worm gear inside the housing.

Use an adjustable wrench to turn the right half (in the orientation pictured) of the tine shaft clockwise, as shown.

Continue to turn the shaft clockwise until it is unthreaded from the worm gear inside the housing.

Step 13

Use a dead blow hammer to tap the right half of the tine shaft towards the worm housing until it can be removed.
If the shaft won’t budge with the dead blow hammer, you can try using a ball-peen hammer instead.

Use a dead blow hammer to tap the right half of the tine shaft towards the worm housing until it can be removed.

If the shaft won’t budge with the dead blow hammer, you can try using a ball-peen hammer instead.

Step 14

Slide the tine shaft assembly out from the left side of the worm housing and remove it.

Slide the tine shaft assembly out from the left side of the worm housing and remove it.

Step 15

              Remove the worm gear

Slide the worm gear up out of the worm gear housing about 1 cm.
Use a flat head screwdriver to separate the right worm gear thrust washer from the worm gear.

Slide the worm gear up out of the worm gear housing about 1 cm.

Use a flat head screwdriver to separate the right worm gear thrust washer from the worm gear.

Step 16

Remove the worm gear and left worm gear thrust washer from the worm housing.
Separate the left thrust washer from the worm gear.
During reassembly, insert the worm gear into the housing before inserting the thrust washers next to it on either side. All three will be aligned properly once the tine shaft is reinserted.

Remove the worm gear and left worm gear thrust washer from the worm housing.

Separate the left thrust washer from the worm gear.

During reassembly, insert the worm gear into the housing before inserting the thrust washers next to it on either side. All three will be aligned properly once the tine shaft is reinserted.

Step 17

Remove the right worm gear thrust washer from the worm gear housing.

Remove the right worm gear thrust washer from the worm gear housing.

Step 18

              Remove the retaining ring

Though the worm gear and tine shaft are shown to be installed in these photos, they should already be removed from your tiller by this point in the procedure.
Use a pair of snap ring pliers to remove the retaining ring from the bottom of the worm housing.
During reassembly, ensure the worm shaft is sufficiently tapped up into the worm housing before reinstalling the worm disk and retaining ring so that the ring properly sits into its recess.

Though the worm gear and tine shaft are shown to be installed in these photos, they should already be removed from your tiller by this point in the procedure.

Use a pair of snap ring pliers to remove the retaining ring from the bottom of the worm housing.

During reassembly, ensure the worm shaft is sufficiently tapped up into the worm housing before reinstalling the worm disk and retaining ring so that the ring properly sits into its recess.

Step 19

              Remove the worm disk

Though the worm gear and tine shaft are shown to be installed in these photos, they should already be removed from your tiller by this point in the procedure.
Use a magnet to remove the worm disk from the worm gear housing.

Use a magnet to remove the worm disk from the worm gear housing.

Step 20

              Remove the engine

Use a socket wrench with an 8 mm socket to loosen the 3/4 inch-long flange bolt from the engine flange. It is not necessary to completely remove the flange bolt.

Use a socket wrench with an 8 mm socket to loosen the 3/4 inch-long flange bolt from the engine flange. It is not necessary to completely remove the flange bolt.

Step 21

Remove the engine from the worm gear housing.

Remove the engine from the worm gear housing.

Step 22

              Remove the drive shaft

Remove the driveshaft from the worm gear housing.

Remove the driveshaft from the worm gear housing.

Step 23

Insert a properly sized bushing driver into the top of the worm gear housing.
If your bushing driver is too short to reach the worm shaft or too large to fit into the housing, You can use a socket extension or large punch instead/in addition the the bushing driver.

Insert a properly sized bushing driver into the top of the worm gear housing.

If your bushing driver is too short to reach the worm shaft or too large to fit into the housing, You can use a socket extension or large punch instead/in addition the the bushing driver.

Step 24

              Tap out the worm shaft assembly

Use a dead blow hammer to gradually tap the worm shaft assembly out the bottom of the worm gear housing.
If the shaft won’t budge with the dead blow hammer, you can try using a ball-peen hammer instead.

Use a dead blow hammer to gradually tap the worm shaft assembly out the bottom of the worm gear housing.

Step 25

              Remove the lower roller bearing.

Remove the lower worm shaft roller bearing from the worm shaft.
During reassembly, install the lower roller bearing onto the worm shaft before using a bushing driver and dead blow hammer to tap the worm shaft assembly, from the bottom, up back into place.

Remove the lower worm shaft roller bearing from the worm shaft.

During reassembly, install the lower roller bearing onto the worm shaft before using a bushing driver and dead blow hammer to tap the worm shaft assembly, from the bottom, up back into place.

Step 26

              Remove the worm shaft

Remove the worm shaft from out the bottom of the worm gear housing.

Remove the worm shaft from out the bottom of the worm gear housing.

Step 27

              Tap down the upper roller bearing assembly

Continue tapping the bushing driver down into the worm gear housing to gradually work the upper worm shaft roller bearing assembly into the gear housing cavity.

Continue tapping the bushing driver down into the worm gear housing to gradually work the upper worm shaft roller bearing assembly into the gear housing cavity.

Step 28

              Remove the upper roller bearing assembly

Use a pair of pliers to remove the upper worm shaft roller bearing from the gear housing cavity.
The gear housing cavity will still be filled with grease, so it may take some time to find these parts with your pliers.
Use a pair of pliers to remove the worm thrust bearing and two worm bearing races out of the gear housing cavity.
The grease should cause these parts to stick together, but if they didn’t, you will need to find them one by one.

Use a pair of pliers to remove the upper worm shaft roller bearing from the gear housing cavity.

The gear housing cavity will still be filled with grease, so it may take some time to find these parts with your pliers.

Use a pair of pliers to remove the worm thrust bearing and two worm bearing races out of the gear housing cavity.

The grease should cause these parts to stick together, but if they didn’t, you will need to find them one by one.

Step 29

              Reassembly tip: pre-install the upper bearing assembly

The next three steps describe how the reinstall the worm shaft assembly during reassembly.
Partially insert the worm shaft into the bottom of the worm gear housing.
Use pliers to slip the worm thrust bearing and bearing races, in order, over the top of the worm shaft.
The worm thrust bearing should lie in between the bearing races while on the worm shaft.
Slip the upper worm shaft roller bearing onto the worm shaft so it lies on top of the upper bearing race placed previously.

The next three steps describe how the reinstall the worm shaft assembly during reassembly.

Partially insert the worm shaft into the bottom of the worm gear housing.

Use pliers to slip the worm thrust bearing and bearing races, in order, over the top of the worm shaft.

The worm thrust bearing should lie in between the bearing races while on the worm shaft.

Slip the upper worm shaft roller bearing onto the worm shaft so it lies on top of the upper bearing race placed previously.

Step 30

              Reassembly tip: Reinstall the lower roller bearing

Re-install the lower worm shaft roller bearing onto the worm shaft and push the entire assembly up until you meet resistance.

Re-install the lower worm shaft roller bearing onto the worm shaft and push the entire assembly up until you meet resistance.

Step 31

              Reassembly tip: tap assembly back into place

Use a bushing driver and hammer to tap the bottom of the worm shaft assembly until it is fully seated and there is enough room to reinstall the worm disk and retaining ring.

Use a bushing driver and hammer to tap the bottom of the worm shaft assembly until it is fully seated and there is enough room to reinstall the worm disk and retaining ring.

To reassemble your device, follow these instructions in reverse order.

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Author

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                    Tarun Thiruma

Member since: 11/20/2019

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Introduction#

What you need#

Introduction

What you need