Topic: Which Crankshaft Bearings? CB750 K3

[odin836]

So many crankshaft bearings to choose from, wanting to replace all during rebuild...
My engine is a CB750 K3, which bearings will suit my needs and what is meant by BLACK, BROWN, GREEN etc?

Thank you!


6   SKU: 13315-300-013
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0190538) (DAIDO)   10   $10.02
6   SKU: 13315-422-003
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0792333) (DAIDO)   10   $10.02
6   SKU: 13315-425-003
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0715961) (DAIDO)   10   $10.02
6   SKU: 13316-300-013
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0190546) (DAIDO)   10   $10.02
6   SKU: 13316-422-003
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0792341) (DAIDO)   10   $10.02
6   SKU: 13316-425-003
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0715979) (DAIDO)   10   $10.02
6   SKU: 13317-300-013
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0190553) (DAIDO)   10   $10.02
6   SKU: 13317-422-003
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0805200) (DAIDO)   10   $10.02
6   SKU: 13317-425-003
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0715987) (DAIDO)   10   $10.02

[voxonda]

Hey Odin,

To determin which bearings you need, check the code on your casing and the code on your crank. These codes give way which size the bores in the casings are and what size the jounals of the crank are.
The color code on the bearing give you the thickness off the bearing.

You'll find good explanation in shop manuals you can download. Look here: http://forums.sohc4.net/index.php?topic=426.msg447970#msg447970

Rob

[CB750F2]

Also read topic 55330.

[odin836]

I reviewed my order from CycleX and forgot that my Lightened and Balanced crank comes with OEM Bearings.
That said, I still need to find "Crankcase bearings" (aka Haynes Manual = "Crankshaft Bearing Shells"?)

As you can see the identifiers listed on page 42 of the PDF are not in existance on either Crankcase or Crankshaft?  Machined off???  If so, given I have the newly balanced Crankshaft on the way, whats my best option?

[754]

Looks like markings are on top crank pic? Move your light around they can be hard to see in some kinds of lighting, they are lightly etched or scribed.

 You can always measure them with a micrometer , wait a second, umm, that would sorta be a bit like engine building ..

What do you mean, you cannot find numbers on your case, are they ground off?

[MCRider]

First, often when you have a crank lightened the codes are machined off. If you're missing one or the other, case codes or crank codes, then that method is off the table. Also, if your crank journals have been polished by CycleX, the crank codes would be meaningless.

The crankcase codes are 5 letters in a row stamped on the outside of the engine in the front on a flat part of the casting. You're pictures are in the wrong place. Nevertheless I suggest plastigage.

I wouldn't use it (the code method) even if i could. Use plastigage, this is a simple operation. The Clymer manual explains how to use plastigage. There are several threads here as well.

A stick of plastigage is less than $2 at auto supply. (edit) There are a few different colors of plastigage based on the clearances you're measuring. Coincidentally, for this purpose you'll need a stick of green plastigage.

Likely you'll end up with all greens, some engine builders just throw in all greens and be done with it. But for peace of mind, use plastigage. Google plastigage and you'll get how to's as well. Simple.

My crank is fairly well used, I ended up with 3 greens and 2 browns. I'm setting it up on the tight side of average.

[754]

You can always measure them, better be used to reading tenths... of a THOU..

I want to see the pic of the engine case where they are missing.

[MCRider]

So many crankshaft bearings to choose from, wanting to replace all during rebuild...
My engine is a CB750 K3, which bearings will suit my needs and what is meant by BLACK, BROWN, GREEN etc?

Thank you!


6   SKU: 13315-300-013
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0190538) (DAIDO)   10   $10.02
6   SKU: 13315-422-003
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0792333) (DAIDO)   10   $10.02
6   SKU: 13315-425-003
BEARING A, CRANKSHAFT (BLACK) (Honda Code 0715961) (DAIDO)   10   $10.02
6   SKU: 13316-300-013
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0190546) (DAIDO)   10   $10.02
6   SKU: 13316-422-003
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0792341) (DAIDO)   10   $10.02
6   SKU: 13316-425-003
BEARING B, CRANKSHAFT (BROWN) (Honda Code 0715979) (DAIDO)   10   $10.02
6   SKU: 13317-300-013
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0190553) (DAIDO)   10   $10.02
6   SKU: 13317-422-003
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0805200) (DAIDO)   10   $10.02
6   SKU: 13317-425-003
BEARING C, CRANKSHAFT (GREEN) (Honda Code 0715987) (DAIDO)   10   $10.02

There are only 4. Black, Brown, Green. Yellow. The latest part numbers are the only ones you can get, the others are discontinued. -425-

Black would go on a journal with the most clearance, and so on. That might be backwards, but you get the idea.

95% of journals I've seen and heard about use Greens.

Use plastigage and you can't go wrong.

[CB750F2]

Your picture and comments suggest to me that you are looking for the crankcase markings on the internals of the crankcase. They can be found externally at the front  of the top crankcase. There is a ledge along the front and this is where the stampings are. Either look from underneath or turn the top crankcase upside down. I suggest as others have to use plasti gauge to check your existing bearings and then go from there. This has been covered recently in a previous post. See my first reply to this post for the number of the post. Pat

[odin836]

Your all correct - I was looking in the wrong place initially.

However the markings are that faint that the only way I could get them to show was to rub grey pencil over the ledge and give it a quick wipe with a damp cloth.... 

The PDF confused me, i was looking for a stamp of some kind inside the case.

Attached is a photo of their location, I hope this helps someone in the future.


There are definately no markings on my crank, despite how it looks in the photo (poor focus, sorry).

Also, if your crank journals have been polished by CycleX, the crank codes would be meaningless.

Guess I'll have to use plastiguage anyway...

Thank you all for your assistance, again this is certainly the forum has proved invaluable!

[MCRider]

Now to further the conversation, as the wife is gone and I have some time... what colors are the main bearings from your bike, prior to the teardown?   (Likely all green, with possible exception).

They are marked on the side edge of the shell with a swath of paint.

YOu'll need to buy a new set of 5 those colors to plastigage. No point in gauging the old ones as they are worn though you can for practice.  Then gauge the new ones to be sure they are in clearance.

Likely you'll have 4 or 5 out of five the same color as the originals. THen you'll return whichever set may not work, if any,  and buy the remaining set if necessary.

I was a little off in my memory, but I had 3 greens and 2 browns. After 50k hard miles and a crank polishing, I went to 2 greens and 3 browns. They don't change much unless you or someone has really abused them.

ITs one of those skills like lacing a wheel (easier actually) that is actually easy and very satisfying.

[odin836]

I'll grab some plastigage and wait for the Crankshaft to arrive from CycleX.

Guess I'll have to go with the markings on my case (BBBBB) as its a replacement case I've no idea of what was on prior to breakdown.... 

[MCRider]

I'll grab some plastigage and wait for the Crankshaft to arrive from CycleX.

Guess I'll have to go with the markings on my case (BBBBB) as its a replacement case I've no idea of what was on prior to breakdown....  

I may not have been fully clear. If you don't have both the crank and case codes, then they are worthless to you.

What I was asking for was a visual on the bearings themselves. Since they are replacement cases, there are no old bearings to see.  So simply use new greenies as your starting point.

Rather than ordering the bearings, if you have a friendly dealer with some in stock, he may let you try them out.

[754]

I just can not see a see a dealer, take back a tried out bearing... just can not even imagine that

 First thing that should be done, is check the crank with a mic. It is possible for it to be worn out of code spec.  The valve stems, pistons, bores, rocker shafts all get measured, so why not the crank..

 Also with hi-strength studs, people are talking about only using the nuts several times, so why use them up to avoid measuring.

 FWIW

[MCRider]

I just can not see a see a dealer, take back a tried out bearing... just can not even imagine that

 First thing that should be done, is check the crank with a mic. It is possible for it to be worn out of code spec.  The valve stems, pistons, bores, rocker shafts all get measured, so why not the crank..

 Also with hi-strength studs, people are talking about only using the nuts several times, so why use them up to avoid measuring.

 FWIW

Its not something I've done very often, but in 1980 I had the cases in the back of my Opel kadette, pulled into Greenwood Honda, told them what i was doing and they said fine go for it. I plastigaged the crank in the trunk of my car. Involved a few swaps of shells. Everything is clean, the shells aren't turned, the crank isn't turned, just wipe out the gauge material and hand it back, good as new.

Never hurts to ask.

It only takes a couple, maybe just one try to get them right. In my case, I gauged them with the old main bolts, and set them aside. I will be installing new HD studs and fresh nuts. So no fatigue.

Its easy, cheap, to each their own, but I know how I'd do it and have done it.

[CB750F2]

Ok, if the crankshaft main journals have been polished and so their diameter may have changed then I would measure the journals and use this data to determine if they are an A,B or C. The table in the service manual can then be used to select your bearing colour. Plasti gauge can then be used to confirm the clearances. I think this would give you a very good chance of getting the clearances right first time. Pat

[CB750F2]

Another comment. If you are not experienced in the use of micrometers ask someone who is to do it for you. CycleX may do it for you if they still have the crank. The table in the service manual lists the range of diameters for each group letter. Pat

[754]

The last 2 posts, outline the procedure quite well.

 If you do have an unmarked crank or journal that went under, you may want to mark it, with the codes.


To the OP, the case numbers which you thought were hard to see, are many times easier to see than the crank ones.. you may only see them holding it a certain way, in the right light.. they are quite faint.

 If the innards of the motor are quite black from use, they would be even harder to see.

[john campling]

I am in the same stage at the moment I have Hondaman's book which has been a great help but my maths are sketchy.
Dont go below 0.0012" (0.030mm) is the advice
Mine are 0.0015"  (0.038mm ) to  0.0019" (0.050mm)
so taking the smallest reading 0.0015" and stepping up to the next shell 0.0004"
will give me a clearance of 0.0011" if I am correct.
(Or is it 2 times 0.0004")
So conclusion stick with original colour bearings taking into account they could be worn
Just don't want to order the wrong size
Thanks for any input in advance

[Jerry Rxman Griffin aka MuthaF'er]

My advice would be to Plastigauge the original size bearings and start from there. In all likelihood they will be fine.

[john campling]

That's what i did to get the readings the issue here is just the oil clearances. The original bearings are a bit worn I intend to replace them anyhow whilst I'm in there
cheers