I was going to start a new thread but figured this info is best posted here. This will be a comparison of the type D and type E tensioner assemblies and also an explanation of why I feel that if you have a type D, you should upgrade it to the type E. First, a little tensioner assembly history. As noted at the beginning of this thread, there were several versions over the years, five to be exact. If you study them, you will notice all have a lock nut to hold the adjuster's setting while installing the cover nut, except the type D ......
Therein lies the problem with the type D. Yamaha decided the cover acorn nut could and would act as the adjuster screw's lock nut. Well, it does lock it down but it can sometimes turn the adjuster screw in too as you're tightening it, and there's no way to tell if this has happened. You may end up with a chain that's too tight and that can stretch it out prematurely. Yamaha realized the "error in their ways" after a few years and came out with the type E adjuster, putting a lock nut for the adjuster screw back on there. When comparing the two assemblies, the major difference is quite obvious. The plunger on the type E is longer. The length was added to the plunger head so the same amount of tension can be achieved with the adjuster screwed in less. More of the adjuster screw hanging out the back provides room for the added lock nut .....
When I first compared the assemblies a few years ago, all I had available was my original '78 type D and a type E from an '80 parts motor. All the components appeared the same (spring, adjuster screw, housing, acorn cap nut) except, of course, the plunger. This made upgrading easy - simply swap the type E plunger and lock nut onto my type D. Since then, I have acquired more type E assemblies, some from later models, and have discovered another small difference or change ......
A 2mm thick copper damper washer was used on the type D and some of the earlier assemblies. This copper washer was carried over and used on the first type E assemblies as well. Then, probably around '81 or so, Yamaha came out with a new, upgraded metal/rubber damper washer. This new damper washer is also 1mm thicker ......
But, adding a thicker washer presents a problem. The plunger will now no longer come out flush to the end of the adjuster screw. This would make adjusting per the manual instructions, making the plunger end flush with the screw head, impossible. It also makes observing the plunger for that little bit of needed in-out movement very difficult because it's inset into the adjuster screw head. Something had to change and well, it did. When Yamaha introduced the new thicker damper washer they also shortened the adjuster screw by 1mm .....
So, that means there are actually six tensioner versions, the type A through type D, and then an early and late version of the type E.