Technique: Playing with the height of your dirt bike
Your dirt bike frame is designed to work in a specific way, and when the geometry of the frame is changed, the motorcycle's handling characteristics change. Sometimes you do well, but often you make it worse than it was. Be careful when changing parts on your motorcycle. Standard isn't always as bad as you think.
Size matters! Over the years, dirt bikes have become increasingly taller. Most modern riders would be shocked at how small, low and short a dirt bike from the mid-1970s was. In 2021, Husqvarna took the plunge and made its dirt bikes lower again. Husqvarna shortened the outer fork legs and inner cartridge rod by 10mm. To lower the rear end, Husqvarna extended the link system arms. Since the first track tests with the new Husky, everyone has been raved about the change.
The upper triple clamps on Japanese dirt bikes have front and rear mounting holes with reversible handlebar mounts that allow the handlebars to be positioned in four different locations. In total, the typical Honda, Yamaha, Kawasaki or Suzuki handlebar mounts offer 35,5mm of fore/aft adjustability. This allows taller riders to move their handlebars forward and short riders to bring the handlebars closer to the body.
Kawasaki equips the KX250 and KX450 with adjustable footpegs. The advantage of a 5mm lower footrest is that tall riders' legs have more space and their legs are not bent as much. Additionally, raising or lowering the Kawasaki footpegs can make the handlebars feel higher or lower when you are standing up. As a rule of thumb, tall riders benefit from lower footpegs because they don't have to bend their knees as much when sitting. For the dirt bikes without adjustable footpeg mounting holes, there are aftermarket footpegs that can be raised and lowered.
The cheapest way to lower a motorcycle is to raise the forks in the triple clamps. If your suspension is set up for your weight, we recommend staying close to your preferred settings (usually around 105mm sag). But if your suspension sags less than 105mm and the bike feels high, try lowering your shock spring preload so the bike sags more than 105mm. A longer shock link lowers the rear of the dirt bike. Longer link systems reduce the seat height to approximately 2,5 cm. If you use a lowering link, be sure to raise your fork legs at least 2mm in the triple clamps to keep the dirt bike balanced.
Most factory riders use sawn-off subframes to lower the rear of their machine. To lower a subframe you must shorten the aluminum support points by 5 to 10 mm. This allows the seat height to drop approximately 2,5 cm. The carbon/plastic subframe of a Husqvarna cannot be lowered because no machining is allowed in finished carbon. In other words: carbon is strong as a whole, but if you saw into it it loses its strength.
Shock absorbers can easily be shortened at your local suspension specialist. Please note that shortening the suspension affects the damping of the shock absorber. This changes the rebound and stiffness of the suspension. So that must be compensated. Shortening a fork is more difficult because when you limit the suspension travel with a spacer, the distance between the fork bushing and the center valve becomes smaller. This causes a spike in damping, which is why Husqvarna shortened the outer leg when it shortened the cartridge rod on the 2021 motocross model.
You understand that all of the above changes affect the geometry of your motocross bike. Even the smallest change can have major consequences for the driving characteristics of your beloved machine. Before you put the saw in your dirt bike: look before you leap!
Photos: Wikihow and archive
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