Top Cam chain tensioner/sprocket

1976 Kz900 with 1015 block. Rebuilding the top end and replacing varios bit while I go. I have a number of these tensioner/sprockets available and wondered if anyone had a preference as to which version they would use.

I have a couple of what I believe to be the original 73 versions, very sturdy but the sprocket appears unremovable without grinding off the factory burred over end of the shaft. One is pretty shot but the second is in pretty good shape. I Also have a very servicable, very good shape lighter weight version which appears to have the same sprocket but the shaft is actually a bolt with a collar. the lighter version has smaller rubber pads and spacers/collars for the four hold down bolts.

Do I use the ok heavy one or the very good lighter one?

Both look to be the same height and will fit. Any thoughts. Thanks.

The gizmo you are looking to install is called the cam chain idler assmembly I think. Set the one that looks best to you on the head in place... you can put a couple of the bolts in place and then set your valve cover down on the cylinder head. First thing you will notice if you try using a late 80s idler is that the valve cover WON'T FIT down on the head. The earlier idlers fit fine on the later head with the later cover; that is, the head with the smog ports. I think you can also swap the rubber pads out and I suggest using the pads that are softest. Along those lines, use NEW rubber dampeners on the front and rear cam chain guides. One is the roller type and the other has the chain pusher hanging down. Get new damper pads for the round rubber roller that sits between the chain in the top engine case. Also, buy a NEW chain bumper. That is the bit that sits in the block and is held by a phillips screw and use loctite on the bolts that hold the idler and this screw.

WG, Strangely enough, the "rubbers" are not interchangable from one to the other. the lighter idler has somewhat smaller rubbers and smaller collars that go through the rubber. My inclination is to use the heavier duty version but it does have a little wobble in the bearing. The lighter one is in almost perfect.

Good info! I had never paid much attention. Jeff at Z1enterprises.com can get the rubber parts if you want to use the later/heavier one. I know the KZ900 valve cover won't sit on the later one as I have tried bwhahaha