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Putting power to the groundground power

Speed's Secrets, October 2008

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Fuel re-mapping and performance tuning, Stage I kits, Stage II and III big-bore packages, specialty engines…it’s all great stuff. Taking a stock 60-horsepower Harley-Davidson up to 80-, 90- or 100-plus horsepower opens up a whole new world of motorcycling. More power always means more fun. Speed’s Performance Plus builds and tunes plenty of those high-performance Harleys, too. They do it at events all over the country all the time.
But all the power in the world, the guys at Speed’s are first to caution, won’t mean much if that added oomph doesn’t get where it belongs. That’s to the rear wheel. Add enough power to a Harley and the stock H-D clutch transferring that power simply won’t be up to the job. Fact: A high-performance engine requires a high-performance clutch to go with it, and bagger riders who routinely pack their bikes heavy would be well advised to take a look at their clutches, too, regardless of the engine’s state of tune.
So, do you simply replace the friction discs with some OE-style parts from the dealership, or do you get a little trickier (and generally spend a little more money) and change the size and style of discs for something a bit more performance oriented? Maybe you even change the hub, the basket and style of springs while you’re fiddling behind the derby cover? The truth is there’s no single, definitive answer to any of those questions. Choosing the right high-performance clutch upgrade depends as much on the rider as it does the bike.
“All this doesn’t have to get overly complicated, though,” says Speed’s Wayne Hanson. “Sometimes—a lot of times—all that’s needed is a stiffer, stronger diaphragm spring, and there are lots available. They’re all direct replacements for the weaker, softer OE part.” This won’t be an expensive or time-consuming upgrade, either. Fifty dollars or so and you’ll be in business with all the clutch you need. Now, this is assuming that the stock friction and steel plates are still in good shape, but even replacing them, along with the diaphragm spring, isn’t going to bump the price of this upgrade into the stratosphere. It’s basically a maintenance job and Speed’s does it all the time.

Harleys putting out considerably more power over stock, of course, are going to need more than just a new spring. They’re going to need a completely new clutch and the aftermarket offers many choices. The guys at Speed’s have used and installed them all, particularly liking the Rivera Pro Clutch Kits. Compared to a stock Harley-Davidson clutch, The Rivera Pro doubles the friction surface. There’s a new, special-design hub included with the kit, and to keep things simple and trouble-free the Rivera Pro, just like an OE Harley, uses a diaphragm-style spring. Rivera, and Harley-Davidson Motor Company, feel it’s much easier to keep a diaphragm-type clutch in adjustment and providing equal pressure. There are three different strengths offered for that Rivera diaphragm spring, too; there’s a stock replacement, a medium-strength and for severe use a heavy-duty spring. Rivera offers organic friction material or Kevlar, as well as sintered-bronze plates. Any will fit the stock H-D clutch basket. If you want to get tricky and bulletproof things, Rivera also offers an ultra-strong forged clutch basket. This, of course, is going to cost a bit more than will a new, heavy-duty spring and replacement plates, but when it’s needed it’s needed. As the saying goes, “Speed costs money. So how fast do you want to go?”
When’s the right time to consider a clutch upgrade? If you’ve increased the power of your bike, it’s right now, and if you regularly load that Harley down like it was a Winnebago that time is right now, too. Putting the power where it belongs is critical. The guys at Speed’s Performance Plus make this all-important connection all the time. It’s an essential part of any performance package. Check out their website for the SPP schedule, and when they’re at an event nearby stop in and talk clutches. Don’t let any of that motorcycle fun literally slip away.

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