Tips and Tricks: Engine Case Bearing Installation

With the right tools and basic mechanical skills, engine case bearing installation isn’t as difficult as you might think.

With the right tools and basic mechanical skills, engine case bearing installation isn’t as difficult as you might think. (Mark Williams/)

For most of us, it’s wise to leave a job as delicate and critical as installing engine case bearings in the hands of a professional mechanic. But for those of you brave or skilled enough to give it a try, here are a couple of quick tips and tricks to get the job done.

Before You Get Started

Once the old bearings have been removed from the cases and you have cleaned everything, make sure you have the correct bearings. You also want to make sure you know which bearing goes into the right-side case and which goes into the left-side case. We recommend marking them with a Sharpie to keep them straight. It is also important to know which side goes up and which side goes down. Refer to the service manual as this may vary from machine to machine. Usually, the bearings are marked on one side. The markings can be used to denote either up or down, but in most cases the marks go up.

Step 1: Freeze the bearings.

This is an essential but easy task. Simply put your bearings in the freezer overnight. Most ATV main bearings are press fit, meaning there is very little tolerance between the bearing and the bearing surface. When metal is frozen it shrinks slightly, which makes installing the bearing a little easier.

Step 2: Clean the bearings.

Clean the bearing race surface with a cleaner that removes all of the dirt, oil, and grease and make sure there is no debris present. Use brake or parts cleaner that will not leave any residue on the surface area. Be sure to check for any high spots, which may need to be leveled before installation of the new bearings. You need a clean and even surface for the bearings to rest on.

Step 3: Heat the case.

Be careful with this step, as heating the cases incorrectly can ruin them. Also, make sure to wear gloves and eye protection during this step. Heating the cases can be done several ways, such as placing the case half in the oven at low temperature for 10 to 15 minutes. But it’s not recommended that you try it in your home oven as the process could stink up your entire house with the smell of burned oil.

The second and most popular method we have seen is using a propane or MAPP gas handheld torch, available at your local hardware store. Lay the cases on a metal even surface and heat the bearing area up evenly using a circular motion (see video below). Don’t keep the torch in one spot for too long, as you just want to heat the area up. Why is this step important? As metal is heated it expands slightly, just as freezing shrinks the metal. This will make the next step much easier.

Step 4: Drop in the bearing.

This step is critical and you don’t want to waste any time. Remove the bearing from the freezer and drop it into the bearing slot. You want to do this when the surface is hottest, and the bearing is the coldest. Position the bearing in its slot as evenly and quickly as possible. In some cases the bearing may drop all the way in, which means you can skip the next step.

Step 5: Drive the bearing in.

To drive the bearing in, you’ll need a hammer and bearing installation tool. Before you start to push the bearing in, make sure it’s seated evenly so you don’t drive it in crooked. This can damage the case and render it unusable. If it does not go in evenly, pop the bearing back out with your bearing installation tool and repeat the process.

Drive the bearing in evenly by tapping the bearing downward, keeping the bearing seated evenly as you drive it in. In most cases, you won’t need to use much force, as heating the case and cooling the bearing has opened the tolerances enough for the bearing to just slide in. Make sure you drive the bearing all the way in. Once it’s installed, let the case sit for a while at room temperature. Finally, oil the bearings with assembly lube and repeat the process for the remaining case bearings.

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