Topic: Engine Bearing Replacement

[Kickstart]

One thing I'd like to add: the bearing #22 in this picture is a #6205 Extra Clearance bearing. While standard bearings will work, they will make the shifting of gears 3,4 & 5 stiff when the engine is hot or under power because of the twisting of the crankcases. The Extra Clearance bearings can be had from any bearing house: they are usually associated with very tight press-fitted holes, but here they serve a different purpose. The Extra Clearance is about 0.0004" in the races, to prevent bind and power loss (and extra heating). 
[/quote]

I know this is an old thread, but others will probably find this when searching, and I think there's a mistake here.

Mark, I believe it's bearing #23 6304NR that is the HS (extra clearance) one.  You specify this in your book, and I also noticed the part description on bikebandit shows HS for this bearing.

I believe the correct list should be:

2 x HK2520 Needle Rollers
1 x 3206ATN9 Roller Bearing
1 x 6003 Roller Bearing
1 x 6008NR Roller Bearing
1 x 6204 Roller Bearing
1 x 6205 Roller Bearing
1 x 6205NR Roller Bearing
1 x 6304 Roller Bearing
1 x 6304NR/C3 Roller Bearing


I don't mean to point out mistakes, I just want to make sure others who search for this get the correct information.

[HondaMan]

You're correct about the "C3" designation for extra-clearance bearings. Today, I am finding that many bearing-house employees don't have a clue about that designation, though.

However...if you ask them for an "electric motor shaft bearing", they will [accidentally] get you the very same C3 part.

[Kickstart]

You're correct about the "C3" designation for extra-clearance bearings. Today, I am finding that many bearing-house employees don't have a clue about that designation, though.

However...if you ask them for an "electric motor shaft bearing", they will [accidentally] get you the very same C3 part.

Funny... I think I ran into this problem just this morning.
I went to my local authorized SKF distributor with bearings in hand. I mentioned I wanted the one bearing as an "extra clearance - C3" and the guy was confused.  He asked me if I was sure about it being a C3, because "C3 is the standard clearance".  We then discussed getting C2 for the others, but they gave me nervous looks and said something about it possibly being too tight.  I didn't end up ordering because now I was confused.

What is the standard clearance for our bearings?... I'm guessing if c3 is extra clearance, maybe c2? [Edit - c2 is less clearance than normal... normal is just "Normal"]

[Kickstart]

I was just on the SKF website.  C2 has less clearance than a "normal":
http://www.skf.com/skf/productcatalogue/jsp/viewers/tableViewer.jsp?tableName=1_1_t3&maincatalogue=1&lang=en

So you need to state "Normal" for most of the bearings and "C3" for the 6304NR (and the 6205 if you're following the recommendation in HondaMan's book).

I guess if the bearing shop you go to confuses you by saying C3 is normal... you should politely leave as I did

[Kickstart]

Has anyone had trouble with the standard snap-ring groove dimensions?
I thought I saw another post where someone said they couldn't get the retainer ring to fit into the groove.

I mic'd the thickness of the retainer ring on my 6008 bearing:  it was 0.0787 inches (1.99898 mm).
Per the SKF specifications, the standard groove is only 1.9mm
http://www.skf.com/skf/productcatalogue/Forwarder?action=PPP&lang=en&imperial=false&windowName=null&perfid=105033&prodid=1050330008

Also, the depth of the groove seems a little too deep.  Spec shows 1.59mm.  I didn't measure the depth on mine, but per the diagram in HM's book it's only 1.25mm deep (although, I assume that measurement isn't as critical).

[Kickstart]

OK... I haven't been on the board in a while.

But I did get my new bearings about month ago.  I ordered one of them with the the groove and snap-ring just to see if the groove would work with the existing retaining half ring.

Unfortunately, the retaining half-ring does not fit in the new bearing's groove.  The new bearing's groove is just a little too narrow. 

It's not that big of a deal for me since I still need to have my machinist cut the grooves in the other two bearings anyway... I'll just have him enlarge this one as well.  But for those of you ordering new bearings I would suggest ordering them without the snap-ring and find a machinist to cut the groove to the correct specification for our bikes.

[Terry in Australia]

Your machinist is gonna have fun trying to cut a groove in a bearing's outer ring mate, I doubt if his cutting tools will be harder than the material that he's trying to cut.

He Might be able to grind a slot into it if he's got a thin cutting disc and a steady hand, but otherwise, I can't see it happening.

Not wanting to rain on your parade mate, but I've tried cutting hardened steel before, with limited success. Cheers, Terry.

[bert96]

I know it's an old thread BUT i can't find a place where i could buy C2 bearings,they simply don't have these bearings!?

Canadian bearings don't have it either .They only have C3

Where do you guys find these bearings?


Bert

[City Boy]

Hondaman,could you respond to Kickstarts note that extra clearance bearing is #23 on mainshaft as opposed to #22 which you mentioned in an earlier post.I am a bit confused. Thanks.   Jim

[Terry in Australia]

Sorry Bert, I've only used OEM bearings in CB750 transmissions, in my experience, they very rarely wear out. Cheers, Terry.

[bert96]

Thanks Mick, I've used SKF bearings before with no issues, they were great. 

You use only OEM bearings?! are you sure

[Terry in Australia]

Yes Bert, I've used SKF bearings for wheels, but not in engines. I'm sure they're fine, I just haven't used them in an engine. Cheers, Terry.

[Kickstart]

I know it's an old thread BUT i can't find a place where i could buy C2 bearings,they simply don't have these bearings!?

Canadian bearings don't have it either .They only have C3

Where do you guys find these bearings?


Bert

nobody?

I need a little bit of help!


Bert

You don't want C2, that was a bad assumption I made - I believe I corrected/edited my statement below.

You just want "normal".  BUT... normal is NOT C3 (also known as JEM).  Your bearing place should be able to order it.  I was able to find a bearing place that knew the difference and ordered mine for me.

[Kickstart]

Hondaman,could you respond to Kickstarts note that extra clearance bearing is #23 on mainshaft as opposed to #22 which you mentioned in an earlier post.I am a bit confused. Thanks.   Jim

I'm pretty sure Hondaman just got those mixed up in his post, as his book mentions the 6304NR one needing to be the HS (or extra clearance one).... you can also double check by looking at the bearings in your engine... I think that original bearing might have "HS" stamped on it as well.

At least, I hope so, because that's what I bought to put back in my bike.

[Kickstart]

Your machinist is gonna have fun trying to cut a groove in a bearing's outer ring mate, I doubt if his cutting tools will be harder than the material that he's trying to cut.

He Might be able to grind a slot into it if he's got a thin cutting disc and a steady hand, but otherwise, I can't see it happening.

Not wanting to rain on your parade mate, but I've tried cutting hardened steel before, with limited success. Cheers, Terry.

My machinist was able to do it... sure enough it was harder than he though it would be... he had to purchase some special bit (he showed it to me, but I don't remember what type it was or anything).

Wasn't cheap - charged me $40 per bearing as I recall.... but yes, I've got the grooves all perfectly cut.

Someday I'll actually put the engine back together. 

[Terry in Australia]

40 bucks per bearing just to get the grooves cut? Ouch! I'd be interested to see the tool that he used, all I could think of was a fine cutting disc, I couldn't imagine a lathe or milling machine tool that could cut a hardened steel bearing case, the case is probably as hard as the bearings? Cheers, Terry.  

[Medyo Bastos]

...the case is probably as hard as the bearings? Cheers, Terry.

or supermans knee caps!

[bert96]

It's more clearer,thanks guys for your help!


Bert

[Justin]

Bringing this topic back from the dead for one important question: Are these bearings for ALL CB750 SOHCs, or just for early ones, just for later ones? Hopefully there is some insight into this. I'm about to order new bearings for my 71 cb750 k1

[wohali]

My understanding is that none of the bearings are different unless you have a CB750A (Hondamatic automatic transmission) which I think has an extra bearing. Don't quote me on that last bit though.

[Justin]

My understanding is that none of the bearings are different unless you have a CB750A (Hondamatic automatic transmission) which I think has an extra bearing. Don't quote me on that last bit though.

I know from Hondaman's book that at least the final drive bearing was different between models, although I think his book also states that they're interchangeable..

[PeWe]

My understanding is that none of the bearings are different unless you have a CB750A (Hondamatic automatic transmission) which I think has an extra bearing. Don't quote me on that last bit though.

I know from Hondaman's book that at least the final drive bearing was different between models, although I think his book also states that they're interchangeable..

See service Bulletine from Honda
Russ Collins used a double row bearing in their Cobra build.

[PeWe]

A very informative site that have a good list of the bearings to a CB750F. I think they all are the same as for the K.
https://wrenchandspanner.wordpress.com/2014/12/16/cb750f-transmission-bearings/

[Justin]

My understanding is that none of the bearings are different unless you have a CB750A (Hondamatic automatic transmission) which I think has an extra bearing. Don't quote me on that last bit though.

I know from Hondaman's book that at least the final drive bearing was different between models, although I think his book also states that they're interchangeable..

See service Bulletine from Honda
Russ Collins used a double row bearing in their Cobra build.

PeWe, where are you getting the copies of the service bulletins? I thought that they were available on sohc4.net but I think the links were bad last time I checked...?

[Badluckhonda]

So if you get these bearing from a bearing dealer you have to have grooves cut into them for the half moon clips ?