Up to this point, I had not found any options that looked suitable for my situation.  I needed a way to beef up the clutch without significantly increasing spring force.  That limit on spring force dictated more friction area (i.e. more plates).

I knew that the early model (1990-1995) DR650 had a few clutch parts that were interchangeable with our LS650.  Some of the fiber plates had the same part number, as did some of the steels.  That implied that the splines on the hub and pressure disc were the same as the LS.  The hub lock washers had the same part number, so the splines in the hub for the input shaft should be the same.  The early DR650 clutch has thirteen plates (seven fiber plates and six steel plates).  Maybe there’s some options buried in the old DR.  I ordered a well-used DR clutch assembly on eBay to see what I could learn.

The DR hub and pressure disk are the solution to the problem.  This shows the DR hub (21410-12D01) next to the LS hub.  You can see that the splines look the same.  The DR hub fits the LS transmission input shaft, and the steel plates fit also.  Note that the boss in the center of the DR hub is a lot bigger than the LS.  The DR pressure disk must be used, or the LS pressure disk must be bored out to suit the DR hub.

Here you can see that the LS pressure disk won’t just drop on to the DR hub.  The hole in the center of the LS pressure disk is too small.  It would be easy to bore out, or just use a DR pressure disk.  Other than the hole in the center, the two pressure disks are identical.

It didn’t take long to figure out that the old DR hub was in bad shape.  It had been rode hard and put up wet.  The steel insert in the center of the hub was loose.  I think I could have run it, but mockup seemed to be a better role for the old hub.  I found another one on eBay and ordered it.

The bottom disk gap was .170”.  No problems there.  The basket was free to jiggle so no binding on the fiber plate tangs.

The spring installed height dropped to 24.4mm.  That might need some attention.  It wasn’t going to present a problem with coil bind (that occurs at 19mm), but the spring preload will be increased significantly.  Seemed like a good idea to trim back the release plate a bit to increase the installed height closer to 26mm.  I used a 7/8” end mill to increase the depth of the spring sockets in the release plate.

With the new 13 plate clutch fully assembled, some clearance checks were in order.  I installed the clutch cover and placed the transmission in 5th gear.  The output pulley turned easy and there was no audible indication of rubbing.
 
A quick check with some modeling clay showed that there was clearance all around, but the spring bolts were a little closer than I would like.

I left the waver washer assembly out.  It counteracts the clutch springs during engagement and release, but I don’t think it changes maximum spring load which is achieved at full release (when the clutch lever on the handlebar is pulled all the way in).  Leaving out the wave washer should provide a bit more clamping force at full engagement.  Replacing the special outer fiber plate with a standard fiber plate should add about 2% more friction surface.

This modification adds about 17% more friction surface while keeping spring load reasonably close to stock.  The lever arm position fell right between the marks with a 46.5mm pushrod, so geometry is unchanged.

I’ve put about 100 miles on the hybrid clutch.  It holds WOT just fine.  Not even a hint of slippage.  That’s with stock clutch springs.  It’s much easier to find neutral than the Barnett clutch, and it might even be easier to find neutral than the stock clutch.  Lever pull is light, just like the stocker.

It does have a couple of minor glitches.
 
The stock LS clutch has very progressive and predictable clutch engagement.  This hybrid clutch is not as progressive.  It requires a bit more finesse, especially with a three-inch flywheel.  Anyone with just a bit of experience will have zero complaints about clutch engagement, but a brand-new rider will have a harder time.  I suspect this is due to leaving out the wave washer.

It clunks a bit when shifting from neutral into 1st gear.  That mostly disappears once the oil is fully warmed up.

For those of you who are pushing the limits, this is a practical approach to beefing up your clutch.  In my opinion, it is safer than installing stiffer springs or shimming springs, and a lot easier than trying to thin out your clutch plates.

I hope you find this report informative.  As usual, I welcome your questions and comments.

Stay safe, stay well.

Mike