Today’s discussion is regarding Primary Belt Drives. I’m going to give you the basics, and the advantages of an open belt system.
First, let’s lay out the advantages of a primary belt over a chain. Belt technology these days has produced tough strong belts that are not quite as strong as a chain, but are coming very, very close. These are being produced at a fraction of the weight of a chain. Chain drive sprockets are made of steel, while most belt pulleys are hard anodized aluminum. These pulleys are a fraction of the weight of the sprockets (hmmmm, see a trend here?). When a Belt Drive is installed, you are shaving a big chunk of rotating weight out if your driveline.
What does that do for us? When you twist the throttle, your engine accelerates. It has to move all the components hooking the engine to the tranny, the tranny itself, and the rear drive and wheel. There is a law in Physics that states “everything at rest or in motion tries to stay in that state until an outside force works upon it”. Because of this law, it takes a certain amount of force to make that change. Now, going back to our twisted throttle, it takes a certain amount of time (and force) to accelerate the mass of all the components. If we reduce that mass, the engine doesn’t have to work as hard, and it will accelerate faster. If you have 2 bikes set up the same way, except one has the stock chain primary and the other with a belt drive. Put them side by side and accelerate, the bike with the belt drive will pull away every time.
Ok, now that we know what the advantage of running a belt is, let’s talk about Open Belt drives. The first advantage is we are shaving another 20-25 LBS off the bike by removing the inner and outer primaries. Shaving your bikes weight doesn’t make more power, but that law of Physics jumps back in there and accelerates things faster. That makes it seem like there is more power. The next big advantage of an open primary is you are not limited to the space inside the cases as far as belt width. Higher Horsepower applications require wider belts to handle the stress. Today, we can buy belt drives as wide as 4”. If you can break a 4” belt, you have got extra serious power!!