Matching upper and lower crank cases

[FreddaAbborre]

By a stupid mistake I cracked the lower crank case. Found another lower crank case but got the information that the upper and lower crank cases are matching. That they were bored toghether to fit the crank bearings. Is that so? And by that, is it impossible to use non-matching crank cases? Can my crank cases be "adjusted" in some way to match - how?
The numbers on the upper case "matches" the frame so I would love to keep it that way.

I've had some sleepless nights about this issue so I hope there are some way out of this.

[z1bman]

yes the crankcases are machined as a set as is the cylinder head & cam caps that why they come as a set

[FER]

Get it welded .
fer

[zed1015]

If the lower case is irreparable (which would have to be very bad damage) then bolt the mismatched cases together with the outer crank bearing races in situ but without the hollow case locating dowels and mic them up.
The cases are machined very consistent from engine to engine, especially within the same production run so chances are that the bearing housing bores will be spot on but the dowels may throw alignment off when fitted.
There's a good chance that you will get away with it as is but you need to do some careful measuring and of course know what you are doing.
If everything measures up but the dowels throw it off it's possible to relocate them.
Using odd cases was common practice in racing circles will no ill effect and I bet there's quite a few zeds running around just fine with odd cases without the owners knowledge.

[FreddaAbborre]

If the lower case is irreparable (which would have to be very bad damage) then bolt the mismatched cases together with the outer crank bearing races in situ but without the hollow case locating dowels and mic them up.
The cases are machined very consistent from engine to engine, especially within the same production run so chances are that the bearing housing bores will be spot on but the dowels may throw alignment off when fitted.
There's a good chance that you will get away with it as is but you need to do some careful measuring and of course know what you are doing.
If everything measures up but the dowels throw it off it's possible to relocate them.
Using odd cases was common practice in racing circles will no ill effect and I bet there's quite a few zeds running around just fine with odd cases without the owners knowledge.

I'm not sure if I understand what you mean with "mic them up"?

However I did some testing. I used one of the outer bearing races and tried it in place with the cases pushed together. I tested both sides on both the cracked case and the mismatched case. With the hollow dowel pins in place. It felt like a realy snug fit and I could feel no difference between the cracked case and the mismatched case.
So I went on for a second test.
I used the same method again, but instead of only the race of a crank bearing I used the whole crank. Same result.
And as a third test I followed the same procedure but with both the crank and the grear box in place. Same result.

So, can I draw any conclusions from the tests?

The crack is pretty big but locaded just infront of the starter (meaning a weld wont be visible).
However I discovered that previous owner made some engineering on two lost threads holding the cover for the chain sprocket. He drilled out approx 8-10 mm and filled the hole with polyester plaster and put a threaded pin which would hold the cover. So in order to use the cracked case i will need to have further more welding to be done.

[zed1015]

I'm not sure if I understand what you mean with "mic them up"?

However I did some testing. I used one of the outer bearing races and tried it in place with the cases pushed together. I tested both sides on both the cracked case and the mismatched case. With the hollow dowel pins in place. It felt like a realy snug fit and I could feel no difference between the cracked case and the mismatched case.
So I went on for a second test.
I used the same method again, but instead of only the race of a crank bearing I used the whole crank. Same result.
And as a third test I followed the same procedure but with both the crank and the grear box in place. Same result.

So, can I draw any conclusions from the tests?

The crack is pretty big but locaded just infront of the starter (meaning a weld wont be visible).
However I discovered that previous owner made some engineering on two lost threads holding the cover for the chain sprocket. He drilled out approx 8-10 mm and filled the hole with polyester plaster and put a threaded pin which would hold the cover. So in order to use the cracked case i will need to have further more welding to be done.

I meant use an internal Micrometer to accurately measure the bores eccentricity.
If the cases easily slot together with no force and the dowels in situ it sounds like you may be able to just swap the case.
You need to ensure that the outer faces where the side casings sit are in line where they meet and ideally do some further measurements to check for ovality of the case bearing bores.
I've done this a couple of times and after all the checks they have been a straight swap but can't be too careful.

[FreddaAbborre]

I meant use an internal Micrometer to accurately measure the bores eccentricity.
If the cases easily slot together with no force and the dowels in situ it sounds like you may be able to just swap the case.
You need to ensure that the outer faces where the side casings sit are in line where they meet and ideally do some further measurements to check for ovality of the case bearing bores.
I've done this a couple of times and after all the checks they have been a straight swap but can't be too careful.

Sounds good! Time to do some tool shopping.
Thanks for the help! Will update when an internal micrometer has been aquired.

[needaz1100r]

If the lower case is irreparable (which would have to be very bad damage) then bolt the mismatched cases together with the outer crank bearing races in situ but without the hollow case locating dowels and mic them up.
The cases are machined very consistent from engine to engine, especially within the same production run so chances are that the bearing housing bores will be spot on but the dowels may throw alignment off when fitted.
There's a good chance that you will get away with it as is but you need to do some careful measuring and of course know what you are doing.
If everything measures up but the dowels throw it off it's possible to relocate them.
Using odd cases was common practice in racing circles will no ill effect and I bet there's quite a few zeds running around just fine with odd cases without the owners knowledge.

I'm not sure if I understand what you mean with "mic them up"?

However I did some testing. I used one of the outer bearing races and tried it in place with the cases pushed together. I tested both sides on both the cracked case and the mismatched case. With the hollow dowel pins in place. It felt like a realy snug fit and I could feel no difference between the cracked case and the mismatched case.
So I went on for a second test.
I used the same method again, but instead of only the race of a crank bearing I used the whole crank. Same result.
And as a third test I followed the same procedure but with both the crank and the grear box in place. Same result.

So, can I draw any conclusions from the tests?

Yes - the cases are good to use together.

The crack is pretty big but locaded just infront of the starter (meaning a weld wont be visible).
However I discovered that previous owner made some engineering on two lost threads holding the cover for the chain sprocket. He drilled out approx 8-10 mm and filled the hole with polyester plaster and put a threaded pin which would hold the cover. So in order to use the cracked case i will need to have further more welding to be done.

Cheap enough if you find the right welder.

[FreddaAbborre]

Finally got the last measurements.
The mismatched cas has a bit larger offset compared to the matching case.
Left crank side: 0,18mm vs 0,10mm left
Right crank side: 0,20mm vs 0,12mm
Please see scetch below to see how I measured. A vs B above

And the result for the gearbox. Simular to above.

Does the mismatched case pass?

Should I use the center crank clamp from the mismatch case? So the forces from the cases on the crank will be in line?

[zed1015]

Looks like you are good to go.
Use the centre cap that matches the upper case.
As you can see even the matched cases are not perfect , height wise (D / C) they are very close and not tight which would be the main issue,the run out measurements in other axes are comparable to the mismatched ones.
I would dry assemble with the crank and gearbox and bolt it all up as a final check and ensure that the outer gasket faces are reasonably aligned.
Again check this by bolting on the outer cases, clutch cover etc without gaskets to see how they sit.

[FreddaAbborre]

Looks like you are good to go.
Use the centre cap that matches the upper case.
As you can see even the matched cases are not perfect , height wise (D / C) they are very close and not tight which would be the main issue,the run out measurements in other axes are comparable to the mismatched ones.
I would dry assemble with the crank and gearbox and bolt it all up as a final check and ensure that the outer gasket faces are reasonably aligned.
Again check this by bolting on the outer cases, clutch cover etc without gaskets to see how they sit.

Late night in the garage yesterday and everything is now dry asseblmed. It all goes toghether really smooth! Everything from how the crank lies in its position to how the case covers sits tight over both cases. Looking really good.
As a test I let a powerfull led flashlight be in the case and let the rest of the garage be dark to see if any lights would be seen where there should be no light. Not a light leakage to be seen.

I'll take this as the final Good to go on using the "mismatched" case. Not mismatched any longer...

And having the engine almost mounted I couldn't resist to put on cylinder, head and cover to see how it looks. Pretty good in my somewhat biosed opinon...

Thanks for all the useful help!

Can anyone tell me why pics I upload from the phone is rotated here?