Crank Bearing Calculations

[mack]

This has to be the worst narative I've ever had to follow.
Anyway so my case is stamped with five (4's) and my crank has 1,1,1,1,2 stamped into the left crank web. So if I interpret the directions correctly, I need Browns for 1-4 inclusive and one black for the fifth.
Any plastic test would only reveal if the existing bearings are with in tolerance, if they aren't then you don't move up or down in color like valve shims but rather replace what was installed originally. Correct?
Issue I have is that I'm using the upper case off one motor and putting it on a lower case and crank of another. I'm sure I'm not the first to have to do this, for those that have; what are the odds that both motors will have the same colored bearings and if not how do we marry a possible different color requirement between the upper and lower case journals? Is this a case of sticking in a set of bearings that will fit, then milling the crank to fit the bearings?

[motoman]

This has to be the worst narative I've ever had to follow.
Anyway so my case is stamped with five (4's) and my crank has 1,1,1,1,2 stamped into the left crank web. So if I interpret the directions correctly, I need Browns for 1-4 inclusive and one black for the fifth.
Any plastic test would only reveal if the existing bearings are with in tolerance, if they aren't then you don't move up or down in color like valve shims but rather replace what was installed originally. Correct?
Issue I have is that I'm using the upper case off one motor and putting it on a lower case and crank of another. I'm sure I'm not the first to have to do this, for those that have; what are the odds that both motors will have the same colored bearings and if not how do we marry a possible different color requirement between the upper and lower case journals? Is this a case of sticking in a set of bearings that will fit, then milling the crank to fit the bearings?

Upper and lower case halfs not being a matched set throws another variable in there for sure. I'm sure many here have opted for that, even tho not the best case scenario. I would think if you plasti-gauged the crank bearings and were gonna 'turn' the crank for an individual fit, should be fine, even tho a future owner would be left with some head- scratching if ever gone back into..

[crazy steve]

Ah, deeper yet into the can of worms....

If you're looking for surety on this, I don't think you can get it. Yamaha simply doesn't give enough information to go outside their 'procedure' for bearing replacement. They don't even give the crankshaft bearing journal diameters, so you have no way of knowing what's 'acceptable' if measuring them. As to which bearing to install to hit a target clearance, unless someone has accurate measurements of each bearing size (to .0001" accuracy; unlikely as those tools are horribly expensive), at best it's all a semi-educated guess. Bottom line, install/torque everything and check to see if you're within spec and hope you got the right bearings.

Machining the crank is out due to the lack of specs and true undersized bearings; replacement is the only option, which may or may not correct your problem.

Mixing case halves? Possibly doable, but personally I'd never do it. You'd probably want to be within one 'number' on bearing saddle size or you may have issues with 'roundness' of the bearing saddle, not to mention alignment of the holes which may be the killer. Yamaha only sold the cases as a matched set, I'm sure for that very reason. I'd very carefully check 'register' of the two halves; if it's off at all, that's a no go. I'd mix case halves only as a very last resort... Keep in mind that all the bored holes have to line up, although you may have a bit more latitude with the trans bearings. You can usually get away with mixing cases if they're split vertically, bad idea if split horizontally.

Not what you wanted to hear....

[Yard Dogg]

Yikes. Do you have access to the numbers from the upper case halve that was married to the lower one that you are using? Probably not as you would already have these numbers. Have you considered using plasti gauge near the seams of the case halves to find out if there is a difference in the bore sizes? Probably not the defined way to use plasti gauge but could reveal something about it scientifically if you do it 3-4 times to make sure it's consistent.

I have a friend of a friend who is an expert machinist and he has a shop full of tools. I would bet that he has calipers capable of measuring in the 100 thousand range. When I get my brown bearings in the mail I could take one of my best old green ones to him and one of the new brown ones to find out what the difference in thickness is. That's the best I can do from here.

[mack]

Restore

This restore is certainly testing my patience. If there could be a problem, I've found it. Great learning experience having to get down to smallest nut and bolt issue it seems. I can't wait to get to the wiring harness, If it's anything like the rest of the bike, it maybe easier to build a new one. Not sure how I'm going to tackle this crank issue and the witnessing Steve refers to, something I've never done before but I've been mulling it over and rice paper seems a likely candidate for the mating half's general accuracy. Figure I'll be going through a lot of plastic gauge over the weekend.

[Yard Dogg]

What was wrong with your other case half? Maybe you can find a donor bike and use the parts from both motors to build one.

[mack]

This was

the one that sat for 15 years on a guys lawn uncovered with no plugs in the cylinders and the filter cap was hanging down. he'd cross threaded the bolt and couldn't get it in all the way. The motor was completely seized. After I got it apart, some of the internals looked ok but the lower half can't be saved. Sat full of water for too long. Actually had large rust stelagtites hanging down from the bottom of one and two pistons right to the crank. One solid mass of rust.
I have a spare motor but I'm trying to keep the serial numbers matching. I've spent a great deal of time salvaging the upper case to this end. May have been a waste of time though. However, I don't give up easily.

[DGXSER]

Might be easier to have someone weld up and re-machine the serial number in the spare to match the VIN.

[crazy steve]

Yep, that may prove to be the easiest fix if you're determined to have matching numbers. Cut/trim the number pad off the 'original' case, then machine the pad off the 'new' case. Tig weld the pad on, smooth the welds, and repaint.

If the only damage to the 'original' lower case is the oil filter bolt threads, that could be repaired. Bead-blast or hot-tank any rust out of there (protecting machined areas) and you won't have to deal with any register issues from mis-matched halves....

[mack]

Well it

may very well come down to that, Although the cops up here are very suspicious of that sort of thing. Probably impound it everytime they saw it.
The rust had actually hardened into some kind of molten metal. I tried metal rescue for a few weeks in it but it didn't do anything.
If it had just been the filler bolt thread I'd have just helio coiled it.

[crazy steve]

Mack, I sent you a PM....