Still confused on this guys... There are no numbers on the crankcase to size the bearings like the manual says.

 

Mine too. I'm rebuilding my engine also and I'm in the same boat.

 

Highly doubtful the numbers aren't there. Are you positive you are looking in the correct spot? Also, try finding another block to locate the numbers to verify you know where to look.

Not trying to call you out, but I can't imagine they aren't there.

I also doubt you would need all 2's. If you can't locate the numbers you will have to buy a bearing and try it. Plastigauge won't show much change in bearings anyways but just be sure they are't too tight.

Sorry I can't help ya

 

Yep! The manual shows to look on the rear of the lower crankcase. I looked there and found nothing. I even looked on the upper crankcase, oil pan, and cylinder jug and still nothing...

Here is what the manual says on the subject:

-The numbers A stamped into the crankshaft
web and the numbers 1 stamped into the lower
crankcase are used to determine the replacement
crankshaft journal bearing sizes.

- "J1 to J5" refer to the bearings shown in the
crankshaft illustration.

- If "J1 to J5" are the same, use the same size
for all of the bearings.

- If the size is the same for all "J1 to J5" one digit
for that size is indicated. (Crankcase side only)

- For example, if the crankcase "J1" and crankshaft
web "J1" numbers are "6" and "2" respectively,
then the bearing size for "J1" is:
"J1" (crankcase) - "J1" (crankshaft web) - 1 = 6 - 2 - 1 = 3(brown)

The bolded part leads to be believe that since the crank shows all 2's, then I need to use all size 2 bearings. But the manual is very confusing. Perhaps Yamaha stamps the numbers on the side of the crankcase only if the bearings are out of spec, and then they use other colored bearings to compensate.

 

I take it from the manual that if all the bearings are the same size that only one number 2 will be shown. Not that if the case doesn't have numbers that the crank numbers will be the ones to use.

I think you'll have to try bearings. It may be your case was early production or the numbers wore off. Is there even just one number where the 5 numbers should be?

Looks like you'll be doing this the hard way

 

I thought the crankcase numbers were supposed to be stamped in so they couldn't wear off? There is a number to the right of where the journal numbers should be, but it's oriented vertically and is an odd combinations of letters and numbers, almost like and engine ID number.

 

On my original crank, all 2's. On my replacement, all 1's.

 

Bump! So how do I go about getting the correct bearings? Do I need to buy all the colors and then plastigauge each journal?

Anyone know what size the colors mean exactly?

 

I think I figured it out!!! After working on the motor I found a "6" on the back of the lower crankcase. It's not in the spot that the manual says, but it was clearly stamped in and it makes sense. According to the manual, if there's only one number on the crankcase then the size is the same for all the bearings.

If the size is the same for all "J1 to J5" one digit
for that size is indicated. (Crankcase side only)

So, 6 - 2 - 1 = 3 = BROWN

Can anyone else confirm this?

 

Anyone?

 

For what it's worth, I think you're on to something. Mine has a "5" on the right side in the same place as your "6". It also has the other codes similar to yours, but seemingly totally unrelated to the crank bearing sizes.

If this is the case, what will the clearance be using Yamaha's instructions?

 

Good to hear!

0 = white
1 = blue
2 = black
3 = brown
4 = green

You said your original crank was all 2's... so 5-2-1=2=black
If your new crank is all 1's, then you will need brown bearings like me.

My rod bearings are all "brown" too, good stuff. I would still like someone else to chime in here to make sure this is the right number to use.

 

Yeah, but where will that put us? For example, Yamaha's range is .0006"-.0015". So, if we were to use brown would that put us dead center? What's the difference if we were to use say, green? I ask as I have various articles (which I don't have handy otherwise I'd quote them) which suggest a certain clearance for a race engine. So, how would we go about shooting for a specific clearance?

 

Ah, I would like to know what the physical dimensions are too. What I'm guessing is that they machine the blocks and crank and measure the clearances. Then they use their color system to select the correct bearings to get the clearances right. Then they stamp the number into the crankcase so that the bearings can be replaced without re-measuring the clearances. So to kind of answer your question, I'm assuming that using the original color bearings will get you the correct bearing clearances as indicated in the manual.

The only way to know for sure is to measure, or plastigage. I'm curious how the bearings vary between the colors. The manual doesn't say what to do when the bearings are out of spec other than to select new bearings...

I'll plstigage my bearings when I rebuild the motor and post the results.

 

thats the number your looking for. 6-2-1=3= brown. the numbers on the left tell you that your upper and lower case are a matching set and the number on the right is the main journal size.

 

Just put the loosest bearings in for the most power! lolhttp://www.r1-forum.com/forums/images/smilies/badteeth.gif

 

So anyone know what the colors mean???

 

I finally got around to Plastigageing the bearings. I only did the rod bearings today. On all four I got around 0.045-0.060mm (rough interpolation between the widths). They are mostly within spec (0.034-0.058mm), but on the high end of the spec, but well below the "limit" (0.09mm) as specified by the service manual. I'd much rather have the bearings be on the tight end so I'm not losing oil pressure.

So this brings up the question, which bearings to do I use to make the clearances tighter? Or is this even necessary? I don't really feel like spending another $50 on rod bearings...

 

for crank journals , try to set all clearances equal (as much as possible) .for more power ,use more clearance .
those bearing numbers on crank / case dont say much and only good for a new set of cases / crank on assembly line.

I'd much rather have the bearings be on the tight end so I'm not losing oil pressure.

dont worry , u wont loose oil pressure at all.

 

if you go with bigger clearance run thicker oel.