What the clutch? Why do we carry six different kinds?
Published on March 11, 2019
Clutches are a slippery point in scooter tuning. If your stock one is worn, you should replace it. If you want to go faster, you should probably focus on your carb, engine and variator. If you want to go faster faster, then we should have the clutch talk. A properly fit clutch will optimize your engine’s output while balancing it with your preferred riding style. Think of a blocking sled in football. Your scooter is the sled, you are the engine, and how your clutch is set up determines the running head start you have leading up to impact. If your clutch engages right away because the spring tension is too low or the arms are too light, you are starting right in front of the sled and you will have a harder time pushing the sled. If your clutch engages too late because the arms are too heavy and the spring preload is too high, you are starting too far away, and you will hit your top speed before you hit the blocking sled- meaning you are wasting time and energy to get off the line. The right clutch will put you at the right distance from the sled based on your speed and weight (the engine’s output).
We know that dialing in the clutch is a matter of engine output and riding style, so there isn’t a one-size-fits-all solution. This is why we currently carry six different GY6 clutches. The principles discussed here also apply to QMB139 and Minarelli/JOG engines. How am I supposed to choose? Some of the things you’ll want to look at in choosing a clutch are the weight, pad size and adjustability. A lighter weight clutch reduces rotational mass and the initial energy required to spin it. Bigger pads mean more contact with the clutch bell, which translate your engine’s power to your rear wheel. The adjustability refers to whether or not the clutch has any built-in adjustments. All clutches can be adjusted by replacing springs, changing arms out and even shaving material off of things, but the clutch needs to be removed or disassembled to do this. For our purposes, “adjustable clutch” refers to clutches with an adjustment that can be made to the clutch itself. We’ll start with the stock replacement. SKU 1100-1209 Current Retail Price $36.99 This clutch is a standard GY6 clutch that doesn’t have any adjustment settings. It does feature a brace along the inside that helps prevent the clutch from warping due to the rotational force applied to the clutch arm posts. You can swap out the springs pretty easily by popping this plate off. It weighs 973 g and the pads are 37 mm x 23.5 mm. This is a good option if you’re just looking to replace your worn stock clutch. It is sturdy and will last as long as your old one did.
Next up is the NCY green performance clutch. SKU 1200-1202 Current Retail Price $52.99 This is the same clutch that comes in the NCY GY6 Super Trans kit. It is not adjustable. It has an inner brace. It weighs 1005 g and the pads are 50.5 mm x 22 mm. The bigger pads are a big reason why this is considered a performance clutch. While they may have added a little weight, they are also adding over 27% more contact area than a typical stock clutch. It is also green, which is one of the faster colors, and the fit and finish of this one are head and shoulders above stock clutches.
NCY also makes an adjustable clutch for GY6. SKU 1200-1029 Current Retail Price $65.99 The adjustment on this clutch is unique to all of our other GY6 clutches. There are actually removable weights in the three arms. With the weights installed, this clutch weighs in at 867 g. Removing the three weights drops it down to 789 g. The pads are 48 mm x 22 mm, and it does not have an inner brace.
The plot continues to thicken with the Malossi Delta Clutch. SKU M 5212487 Current Retail Price $159.99 This clutch is made in Italy, a country known for their love affair with speed. It weighs 1054 g and has an inner brace. The pads measure 48 mm x 23 mm. This clutch features a spring preload adjustment that allows you to fine tune the RPM at which the arms release and engage. To adjust the preload, you loosen the Allen bolt and shift the indexed spring retainer plate in the direction you want. Shifting it to the right loosens tension on the spring and allows the clutch to engage to at a lower RPM. Shifting it to the left increases the tension on the spring, meaning the clutch needs to spin at a higher RPM in order to engage.
Our next contestant also hails from Italy. The Polini Maxi Speed Clutch. SKU 1200-1230 Current Retail Price $89.99 It feels like a sports car made entirely of top grain leather. It weighs in at 925 g, even with its inner brace. The pads measure 48 mm x 21 mm. The Polini Maxi Speed Clutch features the most straightforward spring preload adjustment of all our clutches, utilizing easily accessible bolts that run through a captured nut each the spring. This is the only clutch we carry that can be adjusted while installed. If the stock adjustment range doesn’t suit your needs, we carry Polini-specific clutch springs, as regular clutch springs will not work in these.
Last but not least, we have the Dr. Pulley HiT Clutch. SKU: 1200-1179 Current Retail Price $299.99 This clutch is expensive for a reason. It uses a unique actuating method that no other clutch we carry does. Instead of just angling out the arms to apply pressure to the bell, it first cocks them into place and then locks them into place to apply the full outward force to the bell. The point is that your clutch isn’t initially dragging with much force (wearing out pads prematurely) and it is only fully engaged at the optimal spot in your power band. The arm is also being pressed against the bell from two spots, the weight pin and the pillow pin, instead of one. And, this is the only one we carry that made it all the way through med school.
Adjustments are determined by two sets of springs. The clutch comes with the base set installed- four sets of pillow springs and four sets of clutch springs. It also comes with a reinforced bell, three compression spring washers/spacers/shims and a clutch nut lock washer. This thing isn’t messing around. Despite all of its fantabulous technology, it actually only weighs 879 g. The pads are 55 mm x 21 mm. ?It has an inner brace. The HiT Pulley is definitely everything you’d ever want out of a clutch, but dialing in the right combination of springs out of 25 possible setups can seem daunting. This clutch is for three people only: 1. The daily road warrior who has to tackle a lot of hills on his or her commute and wants only the best 2. The track warrior who has already put a big bore, variator, carb, exhaust, etc. on their bike and they’re looking to maximize all of it. 3. The person with too much money who doesn’t ride much anyways. So, if you haven’t already started upgrading your transmission, this clutch is probably overkill. If you have already made a bunch of upgrades, this clutch will kill it.
tl/dr Your clutch setup should be determined by your engine’s power band and your riding style. An engine that peaks around 1000 RPM should have a clutch that engages sooner than one that peaks at 3500 RPM. An improperly fit clutch will either waste your engine’s power by engaging too quickly, making your scooter work harder, or engaging too late and ripping your face off. We carry six different kinds and you should just buy all of them because one of them will work for you. No returns.