American Motorcycle Dealer AMD 223 February 2018 | Page 52

Variable Pressure Clutch – what, how and why? PARTS AND ACCESSORIES Huntington Beach, California based AIM Corp. (Advanced Innovational Machinery) was established in 2001 as the North American affiliate company of Tamachi Industries, Tokyo, Japan – an automotive and specialist component manufacturer that can trace its roots back as far as 1912. One of its specialties has been the development of clutch assist technology, and following the American V-twin industry launch of its Variable Pressure Clutch (VPC) in 2003, AIM has become the market leader for street, sport and cruiser clutch assist applications. Initially developed in the Nitro Harley AHDRA series by Tak Shigematsu (Tak Performance Products), AIM has continued to develop the system with products such as the patent pending CF2 kit, clutch basket with WPC treatment, an advanced friction resistance metal surface treatment that improves durability and performance of critical components, VP-LT, spacer- free VPCs, and VP-SDR (designed with sliding weights for assist and slip clutches such as those used by Harley-Davidson on some of the heavier tourers. Throughout this process of product evolution, one fundamental series of questions has always been at the forefront of dealer and performance engineer thinking – namely, what exactly is a Variable Pressure Clutch, how does it work, and why does it improve clutch operation so dramatically? In explaining the Variable Pressure Clutch, AIM Corp. President Yasu Watanabe started by explaining that “before the Variable Pressure Clutch (VP Clutch) was brought about, the only way to increase your clutch holding capacity was to increase clutch plates or increase the diaphragm spring pressure. “The drawbacks of increasing the diaphragm spring pressure is that the clutch lever becomes stiffer. This makes it very difficult for riders with smaller forearms to pull the clutch lever with higher horsepower builds (without going to the gym!). On the strip, a few seconds of holding a stiff lever isn’t such a big deal. But having to endure a heavy lever during stop and go traffic is when it gets unbearable.” This is where the VP Clutch comes in. The VP Clutch uses centrifugal force with weights and levers to increase the holding pressure of the diaphragm spring as the revs climb. Essentially, using the VP Clutch allows the rider to use a softer diaphragm spring to accomplish what a heavier spring can do! “This allows riders to enjoy their high horsepower engine without the drawbacks of having an extremely heavy clutch lever. In reverse, this also allows for higher horsepower builds with just a heavy spring and VP Clutch.” AIM offers Variable Pressure Clutches with 68, 84 and 95 mm diameter contact points. The stock Harley clutch plate has a 95 mm diameter. “We have found that changing the contact point of the diaphragm spring allows for an easier to pull clutch lever. Leverage allows for the pull to become lighter, but the side effect is that the clutch holding power will be reduced, which causes slippage. “Our solution was to use the smaller diameter together with a Variable Pressure Clutch to allow for reduced lever effort during idle and increase the clutch holding pressure. When applied to the original 95 mm contact point, it becomes stronger than was previously possible with a just a spring.” AIM Corp. continues to push its boundaries and subject its product designs to the harshest of tests… 2017 saw them return to “The Great White Dyno”, which is the proving ground of the Bonneville Salt Flats, with Hiro Koiso and his Pro Charger supercharged Harley, setting three new records and becoming the fastest naked bike to ever run on the salt flats. “Transferring 378 horsepower and 310 torque to the salt is the kind of test that really shows the power and reliability of a clutch, and our CF2 locked on tight, helping Hiro set 216.818 mph in the AMA 3000 A-PBG class, 226.100 mph in the AMA 3000 A-PBF class and a 227.236 FIM recognized speed.” The company’s CF2 (Constant Force) sells as a complete kit for ‘07 and later Big Twin models (including ‘06 Dynas, except for the models with cable clutch control). The kit includes the CF2 lock- up head, CF2 pressure plate, billet clutch inner hub, billet clutch basket and six clutch springs – just add clutch plates and a CF2 shorter pushrod and “feel the power,” says Yasu. AIM CORP. Huntington Beach, California, USA Tel: [phone] [email protected] www.aim-tamachi.com 52 AMERICAN MOTORCYCLE DEALER - FEBRUARY 2018 www.AMDchampionship.com