How to Replace Bearings in a Motorcycle Engine and Transmission

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As many Do-It-Yourself believers have discovered, the joys of dismantling and rebuilding an engine and transmission are few and far-between. The stress of "How am I going to remember how this goes back together?!" coupled with the occasional bit of engine that zips off the work bench out of sight presents a task that is not wholly enjoyable. Probably the least enjoyable task is that of removing parts that are tension set within the engine/transmission casings--specifically bearings. Standard ball bearings in the engine and transmission are typically pressed into place, which makes getting them out again, a bit of an ordeal, but there are a few things you can do to ease the removal of even the most stubborn bearing.

Steps

1. 1
   Have a composition book , some index cards , quart or gallon size baggies and a pen handy . Take the time to make drawings and notes at each step . The "how to" manuals are at their best inadequate . See if you can find an exploded diagram of the motor . Place the parts and pieces in baggies with note cards describing what and where they go . Replace all the seals and bearings not just the ones in doubt .

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2. Mosr bearings and seals can be sourced via a bearing distributor at lower cost than the OEM .
3. 3
   Have the right tools and chemicals . Hondabond or Yamabond is the best all purpose sealant for engine case work though gaskets are always 1st choice . Probably need an impact driver , torx bits and a case seperator tool or can make one usually with 8mm X 1.25 bolts and nuts through a piece of 1/4 inch thick aluminum strip/plate . A little torch heat on the cases and moderate taps with a rubber hammer help split the cases .
4. 4
   A blend of 90 % mineral spirits ( a.k.a paint thinner ) and 10 % motor oil is a good final cleaner . Use a WD-40 or comparable pump sprayer bottle for it available at NAPA or most large box D.I.Y stores in the tool section or near the WD-40 display .
5. 5
   Make sure all the bolts holding the cases together are out . Very easy to miss one .
6. 6
   Pay close attention to location of all shims and thrust washers as cases seperate. Seperate cases laying the motor top to bottom , not side to side . Usually side ignition was located is "bottom" and side clutch was located is " top" . A couple 2X4 inch blocks about 10 inches long help offset end of crank making cases want to pivot while seperating .
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   DANGER -- using a torch will ignite cleaner so it most be wiped off and do torch work outside if possible . Fisrt pass is used to burn off any solvent not wiped off .
8. 8
   Heat the casing that has the bearing mounted in it. This can be accomplished with either an oven large enough to hold the casing or with a propane or other gas torch. If you use the oven, pre-heat it to approximately 105 Degrees Celsius (220 F). Leave the casing in the oven long enough for it to reach the ambient temperature in the oven. An estimated time would be half an hour. In some events, the bearings may fall out while still in the oven. For that reason, it is good to put a baking sheet under the casing, to prevent things from falling on the oven element. If you are using a torch, heat up the area around the bearing for 1-2 minutes , moving the torch always and not allowing the flame to touch anything . May take several 1-2 minutes sessions .
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   Start removing the bearings. Examine the casing to see which direction the bearings must go in order to be removed. In most cases, bearings can only be removed from one direction, so you must press it out from the other direction. In some cases, you may only be able to access the bearing from one direction and must pull the bearing out with limited clearance. That is little to no fun at all. Bearing pullers are available at discount tool supppliers such as Harbor Freight . Seldom needed but a worthy $25 investment .
   • For bearings that can be pushed out, take a socket or bearing driver of roughly the same diameter as the exposed outer ring of the bearing. Place it on top of the bearing from the back side of the casing (The side the casing cannot be removed from) and strike the socket with a dead blow hammer. A ball peen hammer can be used , but make sure you eae into the blows and the case is not laying on a heard surface like concrete . Wood is best . This should remove the bearing. Make sure the case is laying flat so the blow does not distort the case or crack it .
   • For bearings that must be pulled, make sure the casing is very hot, turn the casing over and strike the casing from behind with your dead blow hammer. If this fails to move the bearing, try taking an eye dropper of cool water and drip it onto the bearing. (Use an eye dropper as to not get cool water everywhere, which may crack a very hot casing.) and try again. If that fails, you may need a special extracting tool to remove the bearing.
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    Fit your replacement bearings in place. Because the replacements should be relatively cool,especially if you place them in the freezer for 30 minutes and handle with gloves or a paper towel , they should slide in much easier than the old bearings came out. A little WD-40 in the hole helps. Be sure to do this while the casings are still hot and its OK to reheat them .
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    Try to prevent damage to the new bearings during installation. To accomplish this, you must insert the bearing in a way that prevents pressure from occurring on the inside ring of the bearing. A good way to accomplish this is to place your old bearing on top of your new bearing, then , using your dead blow hammer, strike the old bearing, which will somewhat evenly distribute the pressure on the new bearing.
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    Repeat process until all of your replacement bearings are in place. If you have a keen ear you will hear a change in the sound of the blows when the bearing seats fully .
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    Feel the bearing turning it for smoothness . Absolutely no roughness is allowed . If any , start over with another bearing .

    
    

Tips

• The primary concerns in replacing the bearings are:
  1. To prevent damage to the casing
  2. To prevent damage to the new bearings
• In some situations you may want to to preserve the old bearings long enough to get sufficient data about them so you can purchase appropriate replacement bearings.

Warnings

• Work with clean parts.
• Do not apply pressure to the inside ring of the bearings.
• Wear heat resistant gloves that allow for good grip.
• For a variety of reasons, you may find it advisable to wear safety goggles.

Things You'll Need

• New bearings that match the specifications of your old bearings
• An oven or a blow torch (Propane works fine.)
• A dead blow hammer
• Something of a similar diameter to the bearings you are removing (A large socket can suffice for many bearings.)
• Heat-resistant gloves
• Safety goggles (optional)

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