Suspension Service

Everyone knows to look for oil on the fork legs. Fewer people know that most "harsh, inconsistent suspension" complaints are actually a sag problem or a dirty wiper seal, not the oil at all — which is why so many riders chase it with clickers and never fix it.

Why it matters

Fork and shock oil breaks down with heat cycles and gets contaminated over time, just like engine oil. As it degrades, damping gets inconsistent — the bike deflects more off square edges, dives under braking, or feels harsh in small chatter even though it's plush on big hits.

Sag: the free adjustment most riders never touch

Before blaming the oil or the valving, check sag — how much the suspension compresses under the bike's own weight and then with you sitting on it in full gear, ready to ride. Get this wrong and the bike behaves badly no matter how fresh the oil is: too little sag makes the bike feel harsh and deflect off small bumps (it's not using its travel), too much sag makes it feel vague, dive under braking, and bottom out on bigger hits. Most full-size motocross bikes are set up around a similar range as an industry-standard starting point, but always confirm the exact figures for your specific bike — sag is set with spring preload, not clickers, and it's the single most skipped free adjustment in off-road riding.

Dirty wipers cause more problems than old oil

The dust wiper seals at the top of each fork leg are the first line of defence — and if they're packed with grit, every stroke drags that grit directly across the oil seal underneath it, wearing a groove into a seal that would otherwise last for seasons. This shows up as exactly the same "harsh and notchy" feeling people associate with old fork oil, which is why a full oil change sometimes doesn't fix the complaint at all: the actual problem was never the oil. Wipe the fork legs and dust seals clean after every ride, not just when you remember — it takes seconds and it's cheaper than a seal replacement.

General service intervals

There's no single number that applies to every fork and shock — it depends heavily on the specific design, spring type, and how hard and how often you ride. As a rough starting point many riders use:

• Fork oil: somewhere in the range of 20-50 hours of riding for a basic oil change.
• Full fork seal/bushing service: roughly every 40-80 hours, sooner if ridden in wet/sandy conditions.
• Shock service (oil, seals, nitrogen): often a bit less frequent than fork service, but again varies a lot by shock design.

Treat these as a starting point for a conversation with your manual or a suspension specialist, not as a fixed rule — the correct interval for your specific forks and shock can be meaningfully different.

Signs it needs attention now, regardless of hours

• Oil visible on the outside of the fork legs (a leaking seal).
• A harsh, "notchy" feeling over small bumps that wasn't there before.
• Noticeably more dive under braking, or the bike sitting lower in the stroke than it used to.
• Clunking or knocking noises from the shock linkage.