How-To: Install & Remove Crankcase Bearings With Your BBQ Grill
Sure you could use an expensive press to install bearings for your crank, suspension linkage, & crankcase, but why not take advantage of the thermal expansion properties of the different metals you working with?
Before I get into the easy method, lets take a look at the hard way of doing it.
Hammer & Bearing Driver
During the top and bottom end rebuild of a CRF250R, I did not have access to the easy method I’m about to show you. I ended up using a bearing driver kit and a BFH. I can’t tell you how many negative comments I received using this method, and I’m really not sure why. Sure it looks and sounds bad pounding on the bearing, but that is how some manuals tell you to do it! Also, the force applied from a press are no different than a driver & hammer. At the end of the day, if you apply force to the outer race and drive it in straight, there won’t be any harm done.
The Easy Method
Did you know that the thermal expansion coefficient is 1.5x greater in aluminum than in steel? Therefore it is most beneficial to change the temperature of the aluminum than the steel.
The video shows how heating up aluminum will slightly make the bores expand to where the bearings will drop right in! No tools needed! This method worked great for the KX250F engine rebuild.
I found that the optimum temperature for aluminum should be 140-170°F. Some manuals state do not go over 200°F. I used an IR temperature gun to measure crankcase temp. If you don’t have an IR gun, residual motor oil on the cases will start to smoke, indicating the temp is just right.
What about the bearings? We can shrink them right? You can shrink the bearings by placing them in the freezer or a cooler full of dry ice (haven’t tried that one before). The only thing I do not like about freezing bearings is the moisture in the air will condense on the cold surface of the bearing. In most cases, heating the case will be sufficient.
Here is a funny story and I’m sure many of you may have done this already. Don’t use your mom’s/wife’s oven. You will only be able to do this once and probably never again. You will stink up the house and they will be mad at you. Instead, use your outdoor grill! Place a piece of aluminum foil to protect both the grill and your engine case.
Blind Bearing Removal
The video shows that heat will even get out blind bearings in most cases, which usually requires a special tool. This tool can be expensive depending where you buy it from. I found the Harbor Freight 95987 available at a reasonable cost should you need one.
Other Options to Heat Case
- Propane torch (this method is OK but takes longer and localized heat can warp cases)
- Crock pot (fill with oil and dunk the entire case)
- Hot plate
Comments
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