What's this number?

[soonerbillz]

Started cleaning parts...
Inside the upper case is this number
What's it mean?

[SoCal250]

It's the Yamaha part number family "278"   (i.e., model code)

CRANKCASE ASSEMBLY 278-15100-02-00

[soonerbillz]

It's the Yamaha part number family "278"   (i.e., model code)

CRANKCASE ASSEMBLY 278-15100-02-00

Ok..cool. thanks
Do all YDS7 R5 and RD'S have the same  stamp there?

[SoCal250]

Yes, I believe all the 250/350 models in that era used the same case. The 400s would have "1A100"

[soonerbillz]

I learn, I learn..

[m in sc]

ds7/r5 cases are different in at least one way: no groove for crank seal lip. also different transmission bearing retaining bracket (as in none? cant remember), i think (behind clutch). but otherwise interchangeable.

[soonerbillz]

ds7/r5 cases are different in at least one way: no groove for crank seal lip. also different transmission bearing retaining bracket (as in none? cant remember), i think (behind clutch). but otherwise interchangeable.

I remember reading that somewhere about the crank seal. Supposedly you have to trim the new seals to remove the lip.

[SoCal250]

ds7/r5 cases are different in at least one way: no groove for crank seal lip. also different transmission bearing retaining bracket (as in none? cant remember), i think (behind clutch). but otherwise interchangeable.

Good info. Thanks Mark

I thought there may be a difference, but Yamaha now lists the same part number for all models. The most recent part numbers show that it was first used on the R5 (red text below) but it's the 2nd revision (purple text below). I bet those revisions account for the differences you pointed out.

And I have a '73 parts manual that shows revision "01". I found the tech service bulletin where the change to 01 was announced for the RD250/350 but the specific change is not called out.

278-15100-02-00   CRANKCASE ASSY
278-15111-02-00   CASE, CRANK UPPER
278-15121-02-00   CASE, CRANK LOWER

[m in sc]

yup.

fyi, rds show this on the fiche in the transmission, its that 3 hole bearing plate behind the clutch:

PLATE, COVER
360-17471-00-00

whereas the r5 fiche does not. so, that is def a confirmed difference as well.  this is also where the stepped clutch washer on the input shaft, etc come into play. but thats another thread.