81 kz650 Upper fork bearing Gap

I had to change mine as they were worn out. The tapered races had slight indentations making the steering notchy. This is not supposed to happen with tapered rollers, but with 10 to 15 years, and a lot of miles on streets that are mostly potholes with the occasional 10 foot long smooth area, they developed notches.

If the races are perfectly fine, they will probably match the new bearings so you might not need to change them.

On mine, after cleaning off the grease, I could see a pattern in the races. I couldn't really feel it with my finger, but I could see it. After replacing the races, the steering felt like new again.

There is no other way I can see to get them out easily. A chisel or punch would have nothing to bite onto.

The dremel required a lot of side to side switchback cuts to get across the surface. Each one has the risk of cutting through to the frame tube. I did put some scratches on the frame tube, but no serious cuts. Then you have to put a chisel into the cuts, as a wedge, to hopefully break the last few thousandths. Then there's bearing material dust everywhere, which won't do the new bearings any good, so you have to really clean everything spotlessly. It's doable, but not recommended.

A cheap wire-feed, flux-core, mig from Harbor Freight is probably all you need . They are about $90. Then a mask and gloves and little practice. Bearing races weld silky smooth and easy as long as it's clean.

EDIT: this was for removing tapered bearings which have no way of removing with a punch. The OP photos shows he has tapered races already. I assume they probably match the taper of the new bearings, if not they need to be removed. With it disassembled, I would clean the races and paint them with a Sharpie marker. Then roll the bearings in the races to see if the wear pattern on the ink is even. If only one area makes contact, then the taper may be different. I've never done this, so may be try it with the new bearings and races to see if the ink wear pattern is uniform.

Out of curiosity, if the bike already had tapered bearings, and the races look perfect, why are the bearings being replaced?


Stock ball bearing races can be removed with a punch.

KZB2 650 wrote: Been slowly gathering all the goodies I need for a rebuild from the front tire to the brakes and tapered bearings....... glad I saw this as I could see me making the mistake of leaving the stock races alone if they look good. I take it they come with the bearing kit from all balls ? and has anyone beat them out another way as the dremel scares me and I don't have a welder. Suppose I should look through the manuals but you guys usually have all the answers.

If your bike has the stock ball bearing races you must replace them with the tapered roller bearing races if you install tapered roller bearings. This is because the tapered roller bearing races are very different than the ball bearing races. The All-Balls kit comes with the correct races and bearings.

Removing the old ball bearing stock races is not particularly difficult and does not require a welder or Dremel. The inner circumference of the stock ball bearing race is slightly smaller than the inside diameter of the steering stem tube, so there is an edge of the old race that you can tap against to remove the race. The way I did it was to use a metal rod that would reach through the length of the steering stem tube. I put the rod through the steering stem tube and against the inner edge of the bearing race and gently tapped the race out of the tube. Be sure not to tap repeatedly against the same spot on the race; move the metal rod to opposite spots on the old race so you don't jam the race in the steering stem tube. Just gently work on it until it comes out of the tube; no need to beat on it with a lot of force because doing so might jam it. Once it is removed clean the steering stem tube and apply a small amount of grease to the area where the new race will seat. I used a piece of PVC pipe against the face of the new race when tapping it into the steering stem tube; that way I didn't hit the race with the hammer. Be sure not to repeatedly tap on the same spot when installing the new race or it will jam in the tube. Another tip for installing the new race is to put the new race in the freezer for a couple hours before installing it. That will cause it to temporarily contract a little which should make it easier to install in the steering stem tube. I read that tip after I had finished installing mine, so I didn't try it, but it sounds like a good idea. Ed

In his last reply he said the conversion had been done already. Is the bearing properly seated? I would carefully measure & compare the old stuff to the new. Maybe the previous conversion was done using Kawasaki steering bearings & perhaps the oem race is different than the All-Balls. From the diagrams at Partzilla the KZ750-L3 for example came stock with roller bearings, so you could use eebbaayy pics for comparison. I would think they'd be the same, though.



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I did mine in the 80's with Timken tapered bearings I got from Kaman. It was a common upgrade at the time. The bike sat 15 years so the steering was notchey due to condensation. I had to use a piece of rebar that had a lip from cutting to catch what little area that stuck out. I heated up the outside of the bottom race and drove it out little by little. The All Balls was slightly smaller than the one I installed decades ago. I used the old one to drive the new one in so when it was seated it was easy to drive the old one out.
Steve.

martin_csr wrote: In his last reply he said the conversion had been done already. Is the bearing properly seated? I would carefully measure & compare the old stuff to the new. Maybe the previous conversion was done using Kawasaki steering bearings & perhaps the oem race is different than the All-Balls. From the diagrams at Partzilla the KZ750-L3 for example came stock with roller bearings, so you could use eebbaayy pics for comparison. I would think they'd be the same, though.

He stated he has a 1981 KZ650 and stated ".....glad I saw this as I could see me making the mistake of leaving the stock races alone if they look good." The 1981 KZ650 came with ball bearings in the steering stem (see image below), so assuming his statement that the bike has stock races is accurate it would have ball bearing races rather than tapered roller bearing races. Ed

My mistake. The comment was in regards to the op. doh. I didn't notice that this topic had gotten kind of hijacked. :laugh:

I realize now, the photos the OP were using are Ed's. But the OP does say he already has tapered races in the frame.

Thanks for the knowledge guys. I took it all apart again and accidentally found the old bearing, thought it was lost! They are exactly the same size but the inner race on the new one for some reason is 3mm or so larger. I have no idea why this is the case, might just clean up the old one for now repack it and that should be alright!

Look for good-quality bearings in Rolek store. I got some items from them, they have a wide choice of products and the delivery is quite fast.