Beware the Grenade Plate

If you’re working on a Big Twin Evo or Sportster with a five-speed transmission that starts having clutch problems, you should know about the “grenade plate.” This generally includes all five-speed XL Sporties (1991-2022) and all the Big Twins through 1999 (with the exception of the weirdo early five speeds with the external clutch arm).

Harley clutch packs include 37977-90, the “spring plate.” Better known to the rest of the motorcycle mechanics of the world as a judder spring, this is a sandwich of steel plates and small, simple flat springs. Its inclusion in the center of the pack is intended to absorb driveline shock, smooth clutch engagement, and help plates disengage, since the primary oil can cause surface tension adhesion between the friction plates and the steels.

And it works! Until it doesn’t. Harley fastens these units with brass rivets. As the rivets work loose, they eventually separate and are free to roam in the clutch pack where they generally cause damage in the form of wrecked clutches. You’ll notice this as a motorcycle that is difficult to shift. If you’re repairing one of these; you may be tempted to reassemble it just like the factory manual's exploded diagram. 

If you walk into the dealer, they’ll sell you a factory setup (which is punishingly expensive) or a Screamin’ Eagle 38002-04. That kit eliminates the plate, but it also includes a heavier clutch diaphragm, making for a heavier clutch pull at the lever, which is about the last thing any Harley needs. And the instructions in the upgrade kits specifically caution the installer not to reuse the factory diaphragm.

But even the MoCo knows removing that pesky judder spring is a good idea.

So here’s the low-buck solution: eliminate the spring plate from the clutch stack and add one extra steel and one extra friction plate. They’re close enough in thickness that the clutch pack height stays within spec and you can get the clutch adjusted nicely.

We keep a new “broken” set (pieces missing) here at the shop specifically as a donor part for this conversion. If you’re working on a budget, though, buying two clutch kits might not make financial sense. One lightly used friction/steel with new items can get you by just fine if you have something laying on the parts pile—or one of your existing plates is in good shape; often one is.

There are some companies offering “extra plate” kits as well, and every now and then over the years we’ve seen companies sell friction plates individually. (Steels can usually be had singly, but the friction plates are the challenge to find.)

The five-speed clutch is generally a good design, but the clutch friction plates are no match for metal fragments. This is a reasonably difficult repair to make on the side of the road, so you might want to eliminate yours before that silly thing frags and strands ya out in the sticks. Make the swap and you’ll have a clutch that will give you years of reliable, trouble-free service.