A motorcycle’s gearbox is similar to a manual car in that it allows the rider to input when to disengage the clutch for shifting gears.
As far as most modern bikes are concerned, the difference is that while a car uses a pedal to manipulate the clutch engagement, a motorcycle uses a hand lever.
Still, the fundamental operation should be the same; pull on the clutch lever with your left hand, and the cable disengages the clutch discs, separating the engine’s flywheel from the gearbox so you can shift gears… only this time, your motorcycle clutch won’t disengage?
Here are 16 reasons why!
Table of Contents
1. Clutch Cable Requires Adjustment
This is the most common culprit. Like any metal cable, the more you yank on your clutch cable while you’re roasting roads, the more you’re stretching the cable out.
In time, standard, everyday use will slack out any clutch cable. This is why inspecting, lubricating, and adjusting your clutch cable is a critical part of motorcycle upkeep.
If you go too long without adjusting your clutch cable, it can get slacked to the point that when you pull your clutch lever in, the cable is too loose to disengage your clutch.
- Frequently adjusting your slack is ideal; if you’re having trouble disengaging your clutch, you likely have a cable with too much slake to work the clutch.
- Adjusting the clutch cable is the solution, but be warned: over-tightening your clutch cable can be just as bad.
- Tension stops the friction disks from properly engaging (it causes the opposite problem from the slacked cable, leading to glazed discs, clutch slip, rear-wheel power loss, etc.).
The first step to troubleshooting a clutch that won’t disengage on a motorcycle is to inspect and adjust your clutch cable.
It’s a quick gig requiring nothing more than a wrench and a ruler.
- Measure your clutch cable’s play by carefully pulling on your clutch lever just until you feel it activating.
- Measure the distance between the rear of your clutch lever and its perch to see if the play falls outside of the bike manufacturer’s spec for your year model.
- If the clutch cable’s free-play is greater than the spec in your bike’s owner’s manual, it’s time to adjust your clutch cable. The same goes for if it’s too tight, though that would hinder your clutch on the engage, not the disengage.
- Most bike clutch cables have two types of adjustment devices, a “fine” adjuster up by the hand lever and one down by the motor in the form of a locknut of some sort.
- If your measurement was just a bit off, a few cranks at the fine adjuster up top should be enough to get you where you need to be. Turning it outward decreases the slack (while inward adds to it). That said, if your clutch is failing to disengage, you probably need a more direct adjustment. Head down to the locknut.
- To decrease the slack preventing your clutch from disengaging your pull in your clutch lever, tighten the front nut and loosen the rear to move the locknut away from the lever.
2. Motorcycle’s External Clutch Linkage Is Bent
Your linkage is the setup that connects your shifter to your clutch for gear selection.
If you, a buddy, or your mechanic have ever adjusted the height of your shifter pedal, it was the linkage they were changing. Sometimes applying too much pressure to part of the linkage during adjustments causes bends that hinder its operation.
In other cases, road debris can slam up against it and put a bend in your linkage.
A bend in your linkage can prevent your clutch from disengaging regardless of how it got there.
If you’ve got a bend in your linkage, you’ll either need to readjust it to spec or replace it, depending on how disruptive the damage is.
When adjusting your shifter, take care not to impact your linkage.
3. Failing or Leaking Master/Slave Cylinder (Hydraulic Clutches Only)
Your clutch’s master/slave cylinder is what pressurizes the hydraulic fluid used to engage, disengage, and maintain the momentum of a hydraulic motorcycle clutch.
If your clutch’s master/slave cylinder busts a leak or wears out, your bike’s clutch will fail to disengage.
A broken master/slave cylinder is a big deal on a hydraulic clutch-operated motorcycle, especially if it’s to the point where your clutch isn’t disengaging. It causes a slew of other issues, making it a worst-case scenario and pretty easy to diagnose.
Here are the Symptoms of a Bad Clutch Master/Slave Cylinder on a Motorcycle with a Hydraulic Clutch:
- It’s hard to shift from gear to gear or to find neutral.
- Shifting gears becomes crunchy to the point of it being audible.
- The clutch lever feels like there’s air working against you while you’re pulling it, as if there’s a spongy resistance.
- The bike lurches forward, creeps forwards, or stalls without warning even when the clutch lever is pulled in (AKA your clutch is failing to disengage).
- The fluid in your clutch’s master/cylinder reservoir is low.
4. Broken Motor, Drivetrain, or Transmission Mounts
Here’s another serious problem.
Your bike’s engine, transition, and drivetrain mounts, as the name implies, are the components responsible for mounting the respective systems and keeping them from rattling during operation.
Broken transmission and engine mounts can cause an assortment of issues with your engine, drivetrain, transmission, chassis–including a clutch that won’t disengage–due to the excessive movement and vibration during standard bike operation.
A broken motor mount can damage drive chains and engine hoses, in addition to a variety of other components. IF this is indeed the reason your motorcycle’s clutch won’t disengage, you’ll need to get the piece remounted asap.
A failing transmission mount can shift the gearbox alignment, negatively impacting the connection between its components and the driveshaft.
One of the byproducts of an unmounted transmission is a clutch that won’t disengage.
Here are the Symptoms of Broken Motor or Transmission Mounts on a Motorcycle:
- Clutch Fails to Disengage
- Engine Noises; Clunking, Rattling, and Banging
- Engine Damage
- Drive Chain or Belt Damage
- Hose Damage
- Shifting Engine, Transmission, or Drivetrain, Depending on Which Mounts Are Failing
5. Hydraulic Fluid Needs to Be Flushed (Hydraulic Clutches Only)
If your bike has a hydraulic clutch, your fluid needs to be replaced every so often to prevent contamination.
If the hydraulic clutch fluid is expired, contaminated with dirt or debris, or gunked up, it may prevent your motorcycle’s clutch from disengaging.
- Hydraulic motorcycle clutches are the fav, as far as some bike nerds are concerned.
- They’re easier on the hand when you’re yanking on the lever, and they don’t require cable adjustments like most moto-clutches.
- That said, they have their maintenance requirements, including fluid inspections and level top-offs.
On a bike with a hydraulic clutch, flushing and replacing your hydraulic clutch fluid is a part of basic upkeep.
Using the wrong fluid in your hydraulic clutch is also a problem that can lead to a clutch that won’t disengage, though this is an extreme situation, to be sure.
Still, it’s essential to know which type of fluid your particular year-model bike uses.
On most hydraulic-clutch-equipped bikes, the clutch fluid is the same as the brake fluid.
That said, other bikes use pure mineral oil; it’s best to consult your bike’s owner’s manual to be sure you’re using manufacturer-suggested fluids in your clutch.
Finally, if your bike has air bubbles trapped in the lines, it’ll affect your clutch’s engagement and disengagement, making shifting clunky.
You might notice your hydraulic clutch fluid muddying with discolorization. That’s a sign that the moisture from an air intrusion leaches into the clutch fluid, triggering corrosion.
Failing to replace the corroded fluid will lead to your clutch failing to disengage correctly.
6. Severe Overheating Breaks your Clutch’s Pressure Plate
If your motorcycle clutch gets hot to the point of causing irrecoverable damage to the pressure plate, your clutch will have trouble disengaging.
Overheating can be caused by:
- Improperly fitting or warped flywheel.
- Over-tightened clutch cable.
- Inadequate pressure plate force.
- Poor rider input/clutch slipping.
- Debris corrodes or contaminates your motor oil.
If your clutch overheats due to any of the reasons above, the warping will throw off your pressure plate’s lift until it’s finally broken for good, causing your clutch to fail to disengage.
7. Deformed or Damaged Tangential Leaf Springs
Another circumstance that results in an inadequate lift from your pressure plate is the impact on your tangential leaf springs.
This can be caused by several things, including:
- Excessive slack in the driveline.
- Improper motorcycle towing or transport.
- Improper shifting string transmission with a thrust load.
- Poor tech installation
Just like above, if your pressure plates lift isn’t what it needs to be, your clutch won’t disengage when you pull that lever.
8. Clutch Facing Breaks Off Due to High Revs in Low Gears
Whether it’s from rip-roaring in the redline in low gears for stunting, pulling your clutch lever in, and revving your throttle past the burst speed, or over-correcting on a downshift, a shredded clutch face is a problem.
If a piece of your broken facing gets stuck in your flywheel or clutch pressure plate housing, you’ll have problems with your clutch disengaging, to say the least.
9. Clutch Disk Interference
This is another issue that interferes with your pressure plate lifting operation. It could be due to expansion from overheating, lateral runout, or a poor replacement, but if your disk interferes with the pressure plate’s lift, your clutch will fail to disengage.
10. Dished or Deformed Clutch Disk
Sometimes, when the techs install the input shaft into the clutch disk hub, they dish its center, negatively impacting how it fits into place.
In other cases, the disk gets dished from extreme overheating. Regardless, a deformity in the hub of your disk will damper your pressure plate lift and stop your clutch from properly disengaging during standard operation.
11. Damaged or Burred Hub Spline
On some bikes, the clutch bell housing and crankcase alignment are offset by wobbling, vibration, missing bearings, excessive slack in the input shaft, etc.
If your clutch hub’s spline is worn or incurs damage, it will jam up on the transmission shaft and wear out. Once it starts to break, your burred-up hub spline will stop your clutch from disengaging, causing quite a racket in the process.
12. Hub Spline Corroded
Whether due to running your motorcycle with too little oil, improper greasing when the tech installed your clutch at the factory or if your clutch is just old and poorly lubricated, rust or corrosion will inhibit your hubs fit and, therefore, its function.
The corrosion interferes with the clutch disk’s sliding back and forth on your transmission shaft, sometimes allowing your clutch’s facing against your flywheel, causing friction.
You might notice some clutch grabs early on if this is happening on your motorcycle. Eventually, though, the clutch will fail to disengage.