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.
Remove as many parts as you possibly can. Obviously, you need clear access to the bearings, but also you should consider removing anything on the casing you wish to keep from excessive heat and strain.
Clean the casing thoroughly. We're going to be dealing with a lot of heat and potentially even open flames. Clean away oil and other potentially flammable substances.
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, 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 at least 3 or 4 minutes.
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.
For bearings that can be pushed out, take a socket 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. This should remove the bearing.
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.
Fit your replacement bearings in place. Because the replacements should be relatively cool, they should slide in much easier than the old bearings came out. Be sure to do this while the casings are still hot.
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.
Repeat process until all of your replacement bearings are in place.
The primary concerns in replacing the bearings are:
To prevent damage to the casing
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.
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.)
Safety goggles (optional)
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