Topic: Crankshaft & rod bearings... making me crazy...

[Gustlock]

These things are making me crazy!
Can't seem to figure out how it works...

This is what I found so far in my CB750 F1 (1976) engine (56.000km):
Crankcase journal ID: B = 39.008mm - 39.016mm  (1.5357" - 1.5360")
Crankshaft journal ID: A = 36.000mm - 35.995mm  (1.4173" - 1.4171")
Main bearing shell installed: 5x brown: 14.994mm - 14.998mm  (0.5903" - 0.5904")

The rods show "F" on one side and "2" on the other.
The marks on the Crankshaft say: "J L AAAAA"   -  "P L..."          No numbers after P?... (some very faint marks there use to be something there but I can't tell what they were)...

Crankcase clearly shows B.

Using plastigauge I measured the clearance on the big ends: all about 0.075mm. I figure I have to install black bearings to reduce the clearance as much as possible?

Also using plastigauge I measured the rod bearings: all about 0.050mm. Problem is I don't know what bearing is installed? Can't find any colour marks on the bearing sides... Maybe brown but it could be caused by oil...
What to do what to do? It's all a bit blurry to me...
The 0.050mm clearance is not bad but since I heave the case open I figured I might as well replace the bearings.

A few pics to illustrate everything:

Marks on crankshaft:



Crankshaft bearing clearly showing the colour brown:


various rod bearings, can you see what colour they are (I wiped of the side using a rag)?:

[Jerry Rxman Griffin aka MuthaF'er]

Journal Left AAAAA
Case =                           BBBBB

Matching A with B in the table gives a Green bearing 13317-300-013 with an oil clearance of 20-41 microns

The 2nd letter "P" should also have a "L" next then 4 numbers which are 1 to 5 with 5 not likely

Wish I could see the crank in person. You're doing great so far.

Book says "color code on the bearing end surface"

   

[MCRider]

Never seen a bearing with the color on the "end", always on the side. In my experience. Seen a fair number of shells, others have seen more I'm sure.

[Gustlock]

Thanks for the quick replies
Have been checking the crank markings in the meantime over and over but I can't see any numbers behind the PL... Have tried various light set-ups but no success I will try again tomorrow in daylight

Combining the letters A and B indeed shows a Green bearing but there are 5 sets of brown bearings installed?
 
Quickly checked 2 rod bearings and it maybe looks like a brown colour mark on the 'end surface'? Is this the correct place for the colour marks?

[voxonda]

I have rebuild and build 11 complete engines, and some topends, and never used plastigauge or whatever. Always used the card from Honda and always found to use the green shells, and never had an issue with them. Have witnessed people trying to alter clearances but got into trouble with it. Just my experience.

Rob

[Gustlock]

Hi Rob,
So you are saying stick with the green bearings as prescribed in the manual? Since the clearance is almost at it's max. by installing green ones the clearance will only get bigger? Is that correct?

What do you think about the rod bearings? How can I determine the correct bearings if I can't read the numbers on the crankshaft?

PS nice to seen your website back online

[MCRider]

I guess I'd have to concede I don't know the "right" place for the markings. Book says "end", you may have one marked on the end. I've only ever seen it on the sides. You have a very good example with that brown one. Its usually a very clear and unmistakable swatch about half inch right at the center of the curve, with shiny metal on either side.

As to colors, if the motor was low mileage <30K, I've always seen that hard to go wrong with a full set of greens. But if you've already got some browns, I'd wonder if someone else has been in the engine before you?

[MCRider]

I just fitted my crank and used plastigauge. It took 3 browns and 2 greens. But my crank has over 70K on it, a little wear expected.

[Jerry Rxman Griffin aka MuthaF'er]

When I put my bottom end together the letters all matched up to green and the Plastiguage proved it correct. 30,000 hard miles. Not likely the crank will wear with good lubrication and the nature of the soft bearing shells. Hasn't been that long ago but I do not remember where the color actually was. Guess we need to find someone that has a new bearing in the plastic bag.

Many builders have taken the easy way out and just used bearings with larger clearance irregardless of letters, etc.

[MCRider]

When I put my bottom end together the letters all matched up to green and the Plastiguage proved it correct. 30,000 hard miles. Not likely the crank will wear with good lubrication and the nature of the soft bearing shells. Hasn't been that long ago but I do not remember where the color actually was. Guess we need to find someone that has a new bearing in the plastic bag.

Many builders have taken the easy way out and just used bearings with larger clearance irregardless of letters, etc.

It was just weeks ago for me, 10 new shells, in the bag, all were colored on the side. But there could be some done otherwise I suppose.

[wrenchmuch]

All the bearing I have seen have been coloured on the side as MCRIDER says . I have never seen colour on used bearings but there it is on yours . It might be wise to concede that heat could have made green look like brown . There are different ideas with regards to fitting bearings . BryanJ a Honda tech for years puts blacks in and goes real easy on the break in . Others select bearings by the chart in the manual . Still others plastigage .I used the chart method which called for all green , but when I plastigaged I found I needed (from left to right): 1 grn ,2 brn ,3 blk ,4 blk ,and 5 grn . The 2 black bearing sets  were on either side of the chains . This combination gave me consistant clearances across the engine . Now I have extra greens . You might consider buying only one set of greens for your rods so you can plastigage with a new set, if the numbers for the rods can't be read on your crank . If green is wrong then at least you'll be able to figure out which bearings you need and will only have shelled out for one set .
Mike