Matching shells to crank and cases.

Sp!ke · Post by **Sp!ke** » Wed Sep 19, 2007 1:07 pm

Does anyone know how to interpret the markings on the back of the cases to establish which shells are required?

There's a guy on one of the S10 forums that has put a TDM900 crank and whole top end onto/into a XTZ engine. I quizzed him on what shells he used and he used the TDM900 ones without checking if they would be OK with his crank cases.

Just wondered how to use the markings on both engine cases to find out if his shells are definately wrong before he goes down the route of stripping it all down again.

Anyone?

See http://supertenere.proboards20.com/inde ... 848&page=3

youngy · Post by **youngy** » Wed Sep 19, 2007 1:17 pm

Error you must login to access this forum.

But I would have thought that when you put the crank into the cases, you would check the oil clearance with Plastigauge or similar. If it's out of spec you'd select another bearing size.

This would be regardless of any markings on the cases.

Post by **phuk72** » Wed Sep 19, 2007 1:24 pm

If memory serves me correctly, there should be some numbers etched on the crank and the shells are colour coded.

youngy · Post by **youngy** » Wed Sep 19, 2007 1:31 pm

Indeed so. The crank and cases are numbered. You need both numbers. Subtract the crank number from the crankcase number to get the bearing size code.

Sp!ke · Post by **Sp!ke** » Wed Sep 19, 2007 2:07 pm

Thats pretty much my understanding - thanks guys.

Would the crank numbers not be etched onto the back of the crank cases?

Just wondering if he can do the calcs without stripping down the engine again.

Below is said engine, its apparently XTZ cases with TDM900 everything else. Apparently in his country law dictates that he cant just swap engines so to remain legal he has to retain the XTZ cases.

youngy · Post by **youngy** » Wed Sep 19, 2007 2:19 pm

The crank numbers are specific to the crank.....so they're stamped on the crank, not on the cases.

No idea if they're scratched on anywhere.

Incidentally, what would he do if, say, his chain broke and smashed the cases? Could he put a complete new engine in the bike then?

Sp!ke · Post by **Sp!ke** » Wed Sep 19, 2007 2:49 pm

Good question, not sure, I'll have to ask him.

Maybe it would be a write off.

wicky · Post by **wicky** » Wed Sep 19, 2007 4:07 pm

oil dig out some pics fer ye to peruse regarding numbers etched onto the cases, Emmett had TDM 900 barls, pistons and rods fitted to his TDM 850 and mentioned summit about the Yamaha mechanic struggling to see some numbers etched on the crank webs or such like and apparently having to use a small right angled extension mirror to view them ??

Greg · Post by **Greg** » Wed Sep 19, 2007 8:10 pm

Yuppers, those are the numbers, but I was buggered if I could de-cipher them when I needed shells, I gave up in the end and just swapped the whole motor over...

I admire the engine builders confidence in chancing to luck with his method of shell selection, I wonder if he's a Euromillions lottery winner as well?

Having spoken to the tech guy at Yamaha (years ago now though) the correct bearing size should be correctly determined by the etched numbers - if those numbers don't make any sense (as mine didn;t) then it's out with the micrometer and bore-gauges. IIRC the shells are colour coded according to their thickness, the tables are in the manual somewhere...

Greg

HansJ · Post by **HansJ** » Wed Sep 19, 2007 10:45 pm

Can confirm the above, the numbers on the crank minus the numbers on the back of the engine (between upper and lower engine mount bolts, for Your convenience...) and then check the manual. I tried desperately to understand which colour codes responded to thicker/thinner shells, but never got any good answers. Ended up selecting shells according to the manual, and confirming the play with Plastigage. Funnily enough, I switched shells to see what the difference between two colours would be, and the difference was neglible, more or less...
Engine has run plus 5000 kms with no problems so far.