Mark - You can see all the details of the case changes in my post #5 as notes on the bottom of the Parts Guide. There’s no specifics of the additional circlip but It is displayed in the schematic.

The unstamped case half appears to have 4 bolts for the mag cover which makes it late 69 and on? (i could have this wrong). Not sure of the changes at that stage, but I am sure someone will. 

JGersh wrote: "Mark - You can see all the details of the case changes in my post #5 as notes on the bottom of the Parts Guide. There’s no specifics of the additional circlip but It is displayed in the schematic."

Yes, great pictures and info!  I was just confirming that changes were made to that case half and identifying the serial number ranges... 

(Because as we all know Yamaha parts books aren't the best and the later book could be just a revision/correction but in this case pretty darn sure it's not.)

P.S.  OH!  You said post #5!  I missed that.  Nevermind. 

The last part number for the case supplied is for 15000 and above which would include all the 2 bolt mag cover case sides. Therefore wouldn't there be another part number for the case that uses the 4 bolt mag cover that was somewhere around the 20000's - maybe other changes were also made to the case at this point?

I was discussing RH case half (without snap ring holding seal)

2 bolt vs 4 bolt is LH case half...  there were at least a couple changes there too during 1968.  No specific serial numbers given if I remember correctly.

From what I remember reading, Yamaha discontinues the older versions because the newer versions will work to replace case halves on the older bikes...  perhaps with additional parts needed...  at least through DT1B #34177.

Details in Tech Library manuals...  specifically 71 DT1E appendices. 

Thanks Mark for clearing that up for me.

Sorry, my mistake guys - i better go and make another coffee - it's amazing the difference it makes when you start looking at the right thing. 

Not to worry, Mark is across it.

Really appreciate all the input here, digging into history is something I truly enjoy. Wife and I are raising two girls in a brick schoolhouse in northwest PA that dates back to 1855, have renovated inside and out.
But this 68 ain’t no spring chicken either and here’s a few more tidbits: the left case is four bolt, although I have a two bolt cover painted blue on the inside which came with the bike, ran it with the two bolt over on.

The right crank seal taps in flush with outside surface of crankshaft “ring”. It does seem like a 5-6mm beveled spacer could be fitted around primary drive gear to keep inside perimeter of seal from backing out. Unless that space is needed for play.

Yellowed MADE IN JAPAN label, barely legible.

Bottom front of right case is stamped 3265. VIN on frame is 03325. 

Studs on left case have exposed threads and are ~3mm higher than right side.  

thanks again to all

Your onto something here Mark.  This is the service bulletin that discusses these changes.  It indicates the change from 2 bolt magneto to 4 bolt at #33417 as you stated.  Based on this the replacement left side case half is from a ‘69 DT1B and the new casting is the cause of the misaligned case half’s.  The more interesting part though is the first change notes the elimination of a right side circlip at the same time.  Would that suggest that both of the cases have been replaced with post #33417 case half’s ???

 

Brigsy - My VIN stamps on the frame and left case are matching # DT1-13439 and the # on the bottom right side case is #13944.  I’ve never seen any information on the right side case #. Maybe MartT or others many know more.