YZ Water pump question

[Coolector]

Hi there I put in a new clutch basket in my 82yz 250 last night and noticed that the water pump drive sprocket was loose on the crank shaft. It looks to me that that is the way it works but i'm not sure. I can press the sprocket on to the shaft and it will stay there but I think it may slide off or turn on the shaft making the water pump stop spinning. I looked pretty close and only see a bolt, locknut but no woodruff key or pin to hold this sprocket from turning.
Hopefully I explained this right and someone can help.
I also looked on the Yamaha parts cateloge online at the sprochet assembly and it looks to be all one peice. Could it have been welded and broke?
Thanks Andy

 

[txkawboy]

andy;
am unsure as to what microfiche u r referring, but here is what i see, and it is not one piece...try it...

http://houseofmotorcycles.bikebandit.com/partsbandit/showschematic.asp?dept_id=653761

 

[Coolector]

Thanks Awboy, the part i'm refering to is actually the primary gear set on the end of the crank, you can see what I mean if you look at the www.worldofpowersports.com site under 82 yz250j and go to clutch assembly the part 3 is 5X5-16110-00-00 It looks like one solid assembly on the pic but the outer sprocket on mines moves around the shaft.
Hope I did'nt confuse you.
Thanks