{"id":43771,"date":"2019-06-17T15:25:42","date_gmt":"2019-06-17T06:25:42","guid":{"rendered":"https:\/\/www.decoboco.info\/en\/?p=43771"},"modified":"2026-09-24T13:45:16","modified_gmt":"2026-09-24T04:45:16","slug":"bimota-sb3-steering-stem-bearing-replacement","status":"publish","type":"post","link":"https:\/\/www.decoboco.info\/en\/20190617\/everyday-events\/bimota-sb3-steering-stem-bearing-replacement","title":{"rendered":"BIMOTA SB3 Steering Stem Bearing Replacement"},"content":{"rendered":"
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Basically, we don’t accept any work on foreign bikes. The vehicles we work on like this are long-standing customers, so please note that.
We’re planning to replace the super heavy steering bearing. <\/figcaption><\/figure>\n\n\n\n\n\n\n\n
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We disassembled the fork earlier, but just in case, I saved images so we can put it back together.
These days it’s normal to take photos, but back then we used to draw diagrams…

Time really flies\u2014that’s what this old guy thinks. <\/figcaption><\/figure>\n\n\n\n
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. . . . . I can’t figure out what’s going on here. Is this hole threaded?
Do I need a special tool to turn it? Why is the top bridge split and tightened like that? There’s a mystery structure packed in here. I’ll be careful not to break anything. . . . Observing and proceeding carefully. <\/figcaption><\/figure>\n\n\n\n
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I’d heard that “the upper bearing on the stem is press-fit,” but it looks like it’s never been removed since it was made. . . .
“Really? It’s okay to tap it from the top?” It’s stuck that tight. (It won’t come out even when tapped\u2014it’s rock solid.)

Of course, I made an aluminum collar with a step that fits the shaft bore before tapping it.
Somehow it came out. . . . I was relieved. <\/figcaption><\/figure>\n\n\n\n
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The owner gave me the parts list, and I checked it many times to make sure I didn’t break anything. <\/figcaption><\/figure>\n\n\n\n
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Finally it came out. It’s more like clay than grease. . . . and the steering feels like clay too. . . . which is why it’s so heavy.
It won’t dissolve in mineral spirits, so I had to wash it with white gas to finally get it clean. <\/figcaption><\/figure>\n\n\n\n
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For anyone working on a BIMOTA SB3 in the future, for reference, I believe it’s SKF 639174 26\u00d752\u00d715.
At first I couldn’t read the first two digits\u2014was it 53? 6J?
I managed to decode it. They look the same top and bottom.

When I searched online, it looks like this bearing. <\/figcaption><\/figure>\n\n\n\n
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There was no wear mark at all, and when I lightly rubbed it with Scotch-Brite, it was still totally usable\u2014so we ended up finishing today!
I thought it would be lifted for about two weeks, so in a way we got lucky. <\/figcaption><\/figure>\n\n\n\n
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I applied Neutech NC100 grease generously to both top and bottom. <\/figcaption><\/figure>\n\n\n\n
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So that mysterious object was a handlebar lock! It’s quite an extravagant design, isn’t it? <\/figcaption><\/figure>\n\n\n\n
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Since the upper side is press-fit, I thought I could just squeeze it in\u2014it’s hollow anyway. . . .
But when I looked, the positioning pin from the handlebar lock was in there, so I gave up.

How did I get it in, you ask? I stood on the bench, put my knee against the stem, and tapped from above\u2014super analog. But since it’s a light press fit, it worked. . . . Phew, I’m glad. <\/figcaption><\/figure>\n\n\n\n
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I also polished it at the same time. <\/figcaption><\/figure>\n\n\n\n
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The handling is so much better now! I wish I’d done this sooner\u2014I’m a bit sorry about that myself.
That’s how it went.
We also did an ELF MOTO 4RACE oil change while we were at it.

That wraps up this job. <\/figcaption><\/figure>\n","protected":false},"excerpt":{"rendered":"","protected":false},"author":2,"featured_media":43753,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"pochipp_cv_data":"","swell_btn_cv_data":"","footnotes":""},"categories":[1924],"tags":[118,76],"class_list":["post-43771","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-everyday-events","tag-bimota","tag-front-maintenance"],"_links":{"self":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts\/43771","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/comments?post=43771"}],"version-history":[{"count":0,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/posts\/43771\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/media\/43753"}],"wp:attachment":[{"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/media?parent=43771"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/categories?post=43771"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.decoboco.info\/en\/wp-json\/wp\/v2\/tags?post=43771"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}