Welcome to William’s Tech Tips!
Need to replace your steering head bearings? Here’s what you do…
The condition of the steering head bearings drastically affects handling and safety. If the bearings are too loose, a dangerous head shake can occur. Often, if you tighten the bearings, the steering will feel notchy, and it will be hard to keep a straight line, especially at low speeds. This can be due to the outer bearings actually having notches worn in, where the bearing rollers make contact. It can also be caused by hardening of the grease, where the stiff grease prevents the bearing rollers from rolling smoothly. Very often, it’s a combination of both, and the steering head bearings need to be replaced for optimal and safe handling. This is a job that you can do yourself with the proper tools.
When changing the steering head bearings on your BMW, the most difficult part is removing the old bearings without doing damage to the motorcycle. Here are some tips and suggestions for this job:
[Refer to a repair manual for detailed information, torque specs, etc.
This is just a generic overview and not intended to describe the entire procedure.]
Begin by removing the handlebars, the front wheel, and the fork assemblies. You may also need to remove the front brake assemblies, depending on the model, or maybe you can leave the brake calipers dangling or temporarily secured somehow. Depending on your particular model, you’ll need some rather large sockets or wrenches, generally 32mm and 36mm. Once the forks have been removed, the center nut(s) of the steering stem is removed and so is the upper triple clamp. Pay close attention to the way that wires, cables, and hydraulic lines are routed so that you can get everything back together the way they came apart. Taking several pictures throughout the process is an excellent idea.
With the top yoke off, there will be one more nut on the steering stem. It may be a knurled nut or one with four notches for a ring spanner. With that removed, you can tap the steering stem and lower fork clamp out with a soft mallet or, if you don’t have one, a piece of wood and a hammer. Never hit the steering stem directly with a hard hammer, or you’re likely to damage the threads!
Removal of Outer Race with Kukko Puller:
With the outer race removed, you ALSO need to remove the inner race. First, break apart the bearing roll cage with some pliers and remove the rollers.
To remove the inner bearing race, we recommend a Dremel tool or die grinder with a very thin cut-off disk.
You don’t need to cut all the way through the bearing race. It’s enough to cut a groove about 2/3 through to create a breaking point. Next, take a sharp chisel and a hammer to crack the bearing race apart. A sharp blow with a chisel should be sufficient to crack the bearing apart on the predetermined spot that you have created with the cut-off disk.
Now, with the chisel wedged into the crack, spread the race apart. It will be very easy to remove the inner bearing race from the steering head shaft. Don’t throw this part away quite yet! This part is perfect for use as a driver to install the new bearing (more about this in a bit)!
Now that you’ve removed the old bearing races, it’s time to install the new parts. Beginning with the outer races, thoroughly clean the openings in the frame. The outer bearing races can be driven into the steering head with a suitable bearing driver. This is an item that we don’t currently offer, but you could use the Harbor Freight bearing driver set, item number 95853, or something similar. Make sure that the bearings go in straight and that they’re firmly seated.
Don’t forget your bearings!
For F650, F800 Street Models, F650 CS, it’s part number 7369440.
For Airheads, F650 GS, Older K Models, F800 GS, G650 X, it’s part number 7711080.
Next, you will need to grease the bearings and, for this purpose, we highly recommend Liqui Moly LM47. This grease will not harden over time, and it will offer the absolute best lubrication.
Press the grease into the bearings and be sure that it fully covers all sides of the rollers. Now you can use the cut bearing from before and drive the new bearing onto the steering stem. Turn the old bearing race upside down and, with a suitable punch, seat the new bearing into position by hammering on the old cut bearing and not the new one. Always only apply pressure to the inner race when installing this bearing!
Install the lower fork clamp into the steering head, and then install the greased upper bearing, tapping on the inner race while holding the lower fork clamp until the bearings are seated. You can also use the old cut bearing in this application so that you are not applying direct force to the new part. Reassemble and tighten all of the components previously removed.
With everything reassembled, including the front wheel, proceed as follows:
Leave the lower fork clamp bolts loose, but tighten the upper mounting points to specification. Tighten the adjustment nut of the steering head fully and then back off just a bit. Tighten the top nut on the steering stem. The forks should move smoothly from left to right and hold a straight-ahead position but, when the bars are turned in either direction about 15°-20°, the steering should fall to the full lock position under its own weight. If not, the bearings are too tight. Loosen the top nut, tighten or back off the adjuster as required, and try again until the steering behaves as described. Now, tighten the lower fork clamp pinch bolts. The steering head bearings should be under very slight tension and not loose.
After final assembly, test ride the bike. You should have very easy to control, straight-ahead handling, and the bike should not weave back and forth or hold a set line; otherwise the bearings are too tight. On deceleration at about 15-20 mph, loosen your grip on the bars and smack one end of the handle bar with the palm of your hand (“Bop Test”). If the steering oscillates once or twice and returns to center, you’re spot on! If the steering oscillates increasingly, quickly grab the bars to regain control and return to your shop and increase the bearing preload. The ideal setting is when you can steer the bike with your knees and there is no weaving at slow speeds and, at the same time, the bike passed the “Bop Test”.
PLEASE NOTE: The “Bop Test”, as described herein, is a diagnostic test, and it is something that should only be attempted by a very experienced rider. Of course, I recommend always having both hands on the handlebar whenever riding a motorcycle. The bottom line is, however, this test really works to check the steering head adjustment. Just be careful!
And there you have it! Share this tip with your friends and call or email if you have questions!
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Watsonville, CA 95076