What Are Motorcycle Fork Seals And How Much Do They Cost To Replace?

If you've ridden motorcycles, especially dirt bikes, for a while, you've likely come across leaking fork seals. In our years of amateur racing, my son and I destroyed many sets of fork seals. It happened often enough that changing them became part of the routine when getting our dirt bikes ready for a motocross race. However, just because it wasn't difficult, doesn't mean the job didn't require some insight and specialty tools in addition to your standard motorcycle tool kit.

Motorcycle forks comprise the suspension at the front of the bike. They consist of a pair of aluminum tubes held at the upper end by a triple clamp that also holds the handlebars. At the other end of the fork tubes, caps clamp onto each end of the front axle with the front wheel centered between them.

Depending on your specific model of motorcycle, inside the fork tubes you'll find various combinations of springs, fluid, washers, clips, bushings, valves, and, of course, seals. The springs hold the motorcycle up, compressing and rebounding as bumps in the road are encountered. The bushings ensure the inner and outer fork tubes slide past each other smoothly while the washers and clips hold it all together. The valves (often adjustable) regulate the speed of the fluid transfer to control damping and rebound forces for the smoothest or most effective ride. The fork seals are there to contain the fluid and keep dirt and moisture out of the fork tubes.

Taking your motorcycle to a repair shop for fork seal replacement could cost hundreds of dollars. In addition to an up-charge on the seals and fluids that are required, some shops charge up to $200 per hour. However, with a few basic tools, some ingenuity, and a modicum of DIY skill, you could do the job yourself for the cost of the seals and fluid.

Buying the seals is as easy as heading to the local dealership that services your motorcycle brand, or logging into your Amazon account to have them at your door in a couple of days in most cases. If you order the seals online, you'll need to know the specific model of your motorcycle, and it's a good idea to know the diameter of your fork tubes, typically called out in your owner's manual in millimeters (mm). While you'll find that a particular replacement seal will fit a wide variety of motorcycles. It's not a one-size-fits all scenario.

The good news is that fork seal sets, like the highly-rated Motoku Pack of 4 which also includes new dust boots, cost as little as $11.99 on Amazon. This Motoku set fits several motorcycle models from Harley-Davidson to Honda, Montesa, and Suzuki. For a more intensive fork tube rebuild, consider installing a complete kit that includes new clips, washers, and bolts in addition to the seals and dust boots; however, these kits are more motorcycle specific, and don't forget the fork oil.

You're also going to need some specialty tools, which could include a fork spring compressor, fork seal drivers, and a fork oil level kit, depending on your specific motorcycle model. You can buy all these tools through Amazon or at other retail outlets, but if you're frugal, like me, you can make do with homemade versions.

I used an extra set of hands and a couple of padded screwdrivers to compress the spring enough to get the bolts started. For the fork seal drivers, I used a piece of PVC pipe that happened to be close in size to the inside diameter; I just had to sand the outside of the PVC to fit into the tube. Be sure not to use anything pointy, like a screwdriver, to set the seals in place or you could damage them or the tube.

The fork oil level kit is just a piece of rubber tubing attached to a syringe. The idea is to overfill the fork tube with oil after the tubes are back on the bike and suck out the overage to the specified height. I inserted a stiff wire into the rubber tubing for my DIY kit, but for $12.47, the oil level kit linked above will be tough to pass up if I do another fork seal replacement in the future.

You'll also need a way to hold the motorcycle upright with the forks removed. Check out Harbor Freight's tools for DIY motorcycle mechanics for a suitable jack.