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Koyo main bearings..


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Enessr

 
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Joined: 16 Dec 2025
Location: Rome, Italy
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Koyo main bearings..

Thu Jan 29, 2026 9:31 am » Post: #1 » Download Post

Morning everyone,
Can someone reccomend the proper Koyo engine/gearbox bearings?
Mine are all shagged so whilst I'm rebuilding I'll change the lot.
Problem is that the Koyo codes 6305R refer to atleast 8 different bearings
available...
Some very cheap and the others double the price, €8 to €40. each..
Some have an oil seal on both sides, horrid plastic ball b3aring dividers etc.
So, basically what code matches the high revving mc21 engine?
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ericandchi
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Joined: 03 Apr 2013

Location: Texas
1994 Honda NSR250 MC28SP
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Transmission bearings

Fri Jan 30, 2026 12:44 pm » Post: #2 » Download Post

Im not sure if you have access, but the parts catalogs for all NSRs can be found here:
https://workshop.nsr-world.com/

I've also posted a screenshot here for you just in case. All of the honda part numbers are still available so you can be sure you are getting the correct replacement. If you can't get them in Italy, CMSNL in England has them listed. Prices seem reasonable.

Or if you really want to get fancy like I did on my bike, you can get ceramic hybrid bearings in US from:
https://www.microbluebearings.com/

If I remember, at least one of the original bearings had a seal on one side which effectively just keeps oil on the one side of the bearing, but its not used to contain oil in the case. If you end up getting a bearing with a seal on both sides they pop off very easily. The microblue ceramics are delivered with low contact seals and you have to snap them in if you use them. I remember having to do this.

Hope this helps.
Eric
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Andy
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Joined: 19 Jan 2004

Location: Devon, UK
1991 Honda NSR250 MC21
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Re: Transmission bearings

Thu Feb 05, 2026 11:11 am » Post: #3 » Download Post

ericandchi wrote:
I've also posted a screenshot here for you just in case. All of the honda part numbers are still available so you can be sure you are getting the correct replacement. If you can't get them in Italy, CMSNL in England has them listed. Prices seem reasonable.


CMSNL are in The Netherlands, Eric. Probably ideal for Italy for shipping and tax reasons. I do like the sound of your ceramic bearings though.
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NSR-WORLD.COM

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