How To Install a Clutch Kit on a 1981 Kawasaki KX125 Dirt Bike

How To Install a Clutch Kit on a 1981 Kawasaki KX125

Why replace the clutch on a 1981 Kawasaki KX125?

The 1981 Kawasaki KX125 is a lightweight 125cc motocross twostroke built for aggressive starts and tight, technical riding. Over time the wet multiplate clutch wears from heat, repeated slipping, and oil contamination. Symptoms that justify a clutch kit include slipping under throttle, dragging or grabby engagement, inconsistent lever feel, hard shifting, or a lever that requires excessive travel. Proper replacement restores direct throttle response, consistent power transfer, and crisp shift quality so the little twostroke accelerates like it should.

Clutch system notes for a 1981 KX125

The 1981 KX125 uses a cableoperated wet multiplate clutch with friction plates, steel drive plates, coil springs, a pressure plate, clutch hub, and clutch basket. Because it's cable actuated, check cable free play and condition when finishing the job – a stretched or binding cable can mimic worn plates. Also inspect oil condition; clutch performance depends on correct, clean engine oil for a wet clutch.

Tools & basic supplies

• Socket set and metric wrenches
• Phillips and flat screwdrivers
• Clutch holding tool or strap for hub
• New clutch kit (friction & steel plates, springs as applicable)
• Fresh engine oil and filter or screen cleaning supplies
• Drain pan, clean rags, and parts tray
• Light lubricant and oil for soaking plates

Preparation

Park the bike on a level stand with the engine cool. Create a clean working area and remove the seat and side panels for access. If you prefer to drain the sump before opening the clutch cover, catch the oil; for many riders it's easier to remove the cover then drain oil through the drain bolt after reinstall. Disconnect the clutch cable at the lever to relieve tension.

Removing the clutch cover & initial disassembly

• Clean the area around the clutch cover to prevent contamination.
• Remove the clutch cover bolts and loosen the cover evenly. There may be a small amount of oil seepage – capture it with your drain pan.
• With the cover off, note the orientation of the clutch pushrod, thrust washer, and any keeper or alignment marks. Photographing the assembly helps on reassembly.

Removing the pressure plate, springs, & plates

Loosen the clutch springs in a crisscross pattern to avoid bending the pressure plate. Remove all springs and the pressure plate. Pull out the friction and steel plates one at a time, noting the order and orientation – they typically alternate steel, friction, steel. Keep parts in sequence so you can compare old vs. new. Inspect the thrust washer and pushrod for wear or scoring and set them aside for inspection.

Inspection checklist & what to look for

• Friction plates - look for glazing, uneven wear, burnt surfaces, or thinning. Slight surface darkening is normal; deep grooves or hard spots mean replacement.
• Steel drive plates - check for discoloration, blueing, or warping. Test flatness against a known flat surface; heavy heat marks or warpage require replacement.
• Clutch basket & hub - inspect basket fingers for notching or grooves where plates engage. Notching causes rough engagement and can usually be felt as drag or chatter.
• Inner hub splines - check for play or rounded splines that allow plates to slip on the hub.
• Springs - compare free length and straightness to new springs; if they're fatigued or uneven they should be replaced with the kit springs.
• Thrust washer & pushrod - ensure washers are smooth and pushrod ends are not mushroomed or scored.
• Oil condition - dark, gritty oil accelerates wear. If oil is contaminated, change it and the oil screen or filter.

Preparing new plates

Because the KX125 uses a wet clutch, soak new friction plates in the correct engine oil for at least 15-30 minutes before installation. This reduces initial slipping and helps them bed in quicker. Lightly oil the steel plates as well to prevent dry starts.

Reassembly installing the clutch kit

• Begin reassembly with the correct starting plate as you removed them – many KX setups start with a steel plate against the basket, then alternate.
• Slide each plate fully home into the basket lugs and hub splines, checking for smooth seating and correct orientation.
• Install the pressure plate and then fit clutch springs fingertight to hold everything in place.
• Tighten spring bolts evenly in a crisscross pattern to compress the plate uniformly. Tighten progressively until snug – do not use force that would damage threads or deform parts.
• Reinstall the clutch cover with a clean gasket surface and new gasket if needed. Tighten cover bolts in a cross pattern.

Final oil & cable adjustments

If you drained oil earlier, refill with the proper grade for a twostroke wet clutch and any required premix. Reconnect the clutch cable and set free play at the lever to a small, specified amount of slack at the lever perch – a correctly adjusted cable prevents drag and false slipping symptoms. Operate the lever several times to confirm consistent engagement and check for any leaks at the cover or cable anchor.

Breakin and test riding

After installation, ride gently for the first few tanks to allow the new plates to bed. Avoid aggressive launches and long slipping during initial heat cycles. Expect improved throttle response, firmer engagement, and smoother shifts once the plates seat. If you experience chatter, grabbing, or continued slipping, reinspect basket notching, hub splines, and spring condition.

Maintenance tips specific to a 125cc motocross twostroke

• Aggressive starts and clutch slipping in sand or woods wear plates faster on a 125 motocross bike inspect the clutch more frequently if you race or ride hard.
• Keep oil clean and change it regularly; contaminated oil shortens plate life.
• Check the clutch cable for smooth operation at least monthly – replace if frayed or binding.
• When installing a new kit, also fit new springs if they're included – fatigued springs diminish pressure and cause slipping.

Wrap up

Installing a clutch kit on your 1981 Kawasaki KX125 restores the direct connection between that punchy 125cc twostroke and the rear wheel. With careful inspection, correct plate soaking, even spring tightening, and proper cable adjustment you'll return crisp engagement, reliable power transfer, and better shift feel for trail days or track sessions.

Related Shopping Categories

Shop Clutch Kits for a 1981 Kawasaki KX125 Dirt Bike.

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Shop Clutch Springs for a 1981 Kawasaki KX125 Dirt Bike.

Shop Inner Hubs and Pressure Plates for a 1981 Kawasaki KX125 Dirt Bike.

Shop Clutch Covers for a 1981 Kawasaki KX125 Dirt Bike.

Disclaimer: This guide is provided for general informational purposes only and is not intended to replace your motorcycle's official owner's manual. Always refer to your manufacturer's documentation for model-specific instructions, torque specifications, safety procedures, and maintenance requirements. If you are unsure or inexperienced, consider seeking assistance from a qualified mechanic or technician.