One of the most common problems motorcyclists experience during the course of their riding career is jerking or shaking while shifting.
Shifting problems generally result from failures within the clutch and oil systems, chains and sprockets, or the shifting equipment.
This article explores the most common reasons why a motorcycle jerks while shifting and how to prevent it from happening.
1. Chain is Too Loose
If your motorcycle’s chain is too loose, your bike may jerk while shifting.
A loose chain can result from corrosion due to a lack of routine chain maintenance or improper storage.
That said, even well-kept motorcycle chains wear out over time from the wear and tear of typical use.
Once worn passed a certain point, a motorcycle chain won’t stay tight even with proper cleaning, lubrication, and adjustment.
If your motorcycle chain doesn’t hold its tension due to rust or wear and tear, you’ll have to replace the used chain to restore your motorcycle’s shifting capabilities. This will also prevent the bike from shaking while you shift.
Here are a few quick tips to keep your new motorcycle chain healthy:
- Detail clean and adjust your motorcycle chain and sprockets with moto-manufacturer-recommended cleaner, particularly after long rides in harsh conditions.
- Inspect, adjust, grease, or lubricate your chain per the service intervals outlined in your bike’s owner’s manual.
- Store your motorcycle indoors, under a rugged tarp, where moisture and UV exposure won’t accelerate the rate of chain wear.
Inspecting your chain is a good first troubleshooting step if your motorcycle jerks while shifting, mainly if your bike exhibits the following symptoms:
- Chain teeth skipping over sprockets.
- Erratic power transfer to the wheels, causing uneven movement and shaking while riding.
- Chain slipping, possibly accompanied by a chain slap.
- The motorcycle chain dislodges from the sprocket.
2. Worn or Damaged Chain Sprockets
Damaged sprockets are a common issue that can cause motorcycles to shake while shifting gears.
The chain sprocket, for example, is fundamental to the transmission gear placement, so you’ll notice a clear difference in how smooth your shifting is as soon as the sprockets wear down.
If left unchecked, a failing chain sprocket leads to missed shifts, jerking while changing gears, and can even lead to your moto’s transmission getting stuck in gear.
Fortunately, troubleshooting the chain and sprocket are equally straightforward tasks.
- We suggest wearing gloves while inspecting your chain to avoid soiling your fingers with grease and roar grime or pinching your skin in the chain.
- Tug your motorcycle chain so it lifts away from the rear of your back wheel sprocket.
- A healthy chain will grip the sprocket with force, making it difficult to raise the chain.
- Adversely, a worn chain will pull right off the sprocket, revealing half of the dog tooth.
- Inspect the chain for any rust or inconsistencies in tension, then move on to inspecting your sprocket teeth.
- Spin the back wheel and inspect the whole chain length, watching the sprocket for chips, breaks, corrosion, and worn or missing dog teeth.
As we mentioned in the previous section, loose chains need to be adjusted, and worn chains need to be replaced; the same goes for a broken chain sprocket.
Putting a healthy chain on a damaged sprocket won’t solve your motorcycle’s shaky shifting troubles for long, as damaged sprockets cause uneven wear to new chains.
3. Transmission Gear Interference
A seized or jammed transmission gear is another typical reason a motorcycle vibrates while shifting gears.
The first sign of seized transmission gear is an increase in resistance while you change from gear to gear.
This can be caused by:
- Damaged shifting shafts
- Inadequate gearbox assembly, or
- The interference of a foreign object jammed between gears.
Your motorcycle’s gearbox is composed of multiple parts working together in a dynamic process.
This means that an issue with a fundamental part like a transmission gear is as likely to result from an issue elsewhere in the gearbox system as it is to cause a problem elsewhere in the transmission.
What should you do if you suspect a seized or jammed transmission gear is why your motorcycle shakes while shifting?
In that case, we suggest you take it to the mechanic for a prompt and thorough gearbox inspection before it causes irreparable damage, or you’ll have to replace the whole transmission.
4. Defective Foot Shifter
Your motorcycle can also experience abrasive jerking while changing gears if your foot shifting lever is damaged or the linkage connecting it to your gearbox needs adjustment or is missing hardware.
The shifter/linkage may need to be tightened, raised, or lowered.
In other situations, interference or damage caused by rough roads or debris bends or warps a part of the shifter setup.
Rust, sand, or gravel can also interfere with the shifter action, causing periodic shaking and missed shifts.
Finally, vibrations can loosen hardware until it pops out, causing your shifter’s tension to fall out of adjustment.
It may be that your shifter/linkage is too loose or needs to be raised or lowered to restore proper alignment.
That said, missing or damaged parts in your shifting lever and its linkage need to be replaced before riding.
A compromised shifter risks additional loosening/missing components, stalling, and violent shaking while riding that could cause a crash and injury.
5. Extreme Tension in the Clutch Cable
If your motorcycle’s clutch cable is too tight or looser than the specified adjustment, your shifting will be noticeably rougher, and the bike may shake while changing gears.
Every motorcycle clutch has a slightly different feel, but the physics are similar across the board; your clutch cable needs a specified amount of free play to call into action when it’s time to move the clutch.
If a metal cable lacks slack, it lacks mobility, and the clutch cable will bind to itself.
If the clutch cable has too much tension, the lack of slack can cause your clutch plates to drag when you release your clutch lever to shift.
The lack of cable slack restricts the movement of the plates, and the dragging clutch can cause jerking while shifting motorcycle gears.
Best advice for clutch cable tension:
- The typical advice for adjusting your clutch cable in the field without a manual is to keep it between 2mm and 3mm.
- If you have the owner’s manual for your year model handy, we suggest you follow the adjustment instructions and stick to the specified measurements.
- Even if the 2-3mm adjustment does the trick, if you are stranded high and dry with a bike that shakes when you shift, we suggest you look up the manufacturer’s spec and adjust accordingly as soon as you get back home.
6. Excessive Free Play in the Clutch Cable
Excessive slack in the clutch cable can cause many of the exact shifting and clutch problems as a clutch cable that’s too tight.
A clutch cable with too much free play doesn’t have the tension needed to shift the clutch plates into position for changing gears, causing the clutch to slip.
A slipping clutch can cause many problems, including rough motorcycle shifting and jerking while changing gears.
Best advice for clutch cable tension, continued:
- Again, the manual for your year model motorcycle includes instructions for clutch cable adjustments that have a specified or spec measurement.
- If you don’t have your manual handy and need your motorcycle to stop shaking while changing gears for the remainder of the ride, start by adjusting your cable’s free play to somewhere between 2mm-3mm.
- Take a test ride and feel out the clutch lever. If the action feels too tight, give it a little more slack
- If it’s too easy to pull in, reduce the slack of hair until shifting feels smooth.
Note: All clutch cables wear out eventually, whether from everyday use, moisture, heat, etc. Once worn, the metal clutch cable won’t hold its tension like a new cable.
If you adjust your clutch cable often to avoid rough shifting, it may be time to replace it.
7. Insuffucent Oil Level
Oil and lubrication are critical to all engines, especially smaller ones like motorcycle engines.
Bike motors are interacting systems of fast-moving metal parts working in close range and coming in contact with one another inside a small space, constantly generating heat.
While some motorcycle designs have separate oil supplied for their primary case, the transmission on many motorcycles is kept cool and lubricated by the main engine oil supply.
The side effects of a low engine include:
- carbon deposits and overheating
- an increase of friction and wear-and-tear on your motor’s cylinders, pistons, valves and clutch plates, and transmission gears
Failing to keep your oil at the spec fill level can cause accelerated damage to your clutch and gearbox, triggering your motorcycle to shake while shifting gears.
- A motorcycle’s engine oil needs to kept at the spec level.
- The spec oil fill level varies from bike to bike, depending on make, model, oil, and moto type.
- Your motorcycle should be checked and topped off before and after every long ride, especially when traveling and riding long distances.
8. Low-Quality, Expired, or Improper Oil
Your motorcycle may jerk while you’re shifting if:
- The engine oil you run through your bike’s motor is a different type or grade than the specifications call for
- The oil quality is diminished from use, overworking your motor
- You fail to service your bike per the manufacturer’s suggested intervals.
There are different types of oil, including mineral, semi-synthetic, and synthetic.
Different styles of motorcycle engines require different oil classes, and using the wrong type of oil can cause engine and gearbox damage that will affect shifting and performance, respectively.
The various types of oils also come in different viscosity grades. They include multiple additives and anti-corrosion agents, which may be ideal for specific engines but cause other problems.
The different types of oils also expire or burn past their point of effectiveness at varying times.
Using expired oil, coagulated oil, or oil contaminated with rust, moisture, dirt, fuel, or coolant can cause severe shifting problems, including aggressive vibrations.
9. Clutch Plates are Damaged
Over time, your clutch plates can warp from the constant friction of everyday use.
Clutch plate friction is increased by:
- Excessive clutch cable tension
- “Power shifting” without using the clutch
- Failing to pull the clutch lever all the way in
- Popping the clutch lever out too fast upon releasing
- An improper clutch plate adjustment.
These situations intensify the rubbing and friction between the clutch plates, which causes grinding noises, rough shifting,m and jerking while shifting.
If you catch the problem soon enough, you may be able to adjust your cable and plates before the friction burns the metal sufficiently to cause warping.
Whether your plates need adjusting or replacing, we suggest you take the motorcycle to a mechanic for assessment, as riding with a grinding clutch can cause further damage and collision risks.