Motorcycle transmissions have evolved in remarkable ways over the past few decades.
Still, save a few exceptions, most moto-transmissions are still manual, equipping a hand-actuated clutch.
It’s hard for me to imagine riding a motorcycle without using my gear shifts to manipulate my RPMS; shifting is a huge part of how I ride.
The simplicity of most motorcycle transmissions lends itself to easy troubleshooting, and there’s no time like now for Motor and Wheels to bring you 10 reasons your motorcycle could be having transmission problems.
1. Faulty Shift Mechanism
A motorcycle transmission’s shift mechanism is a critical component of the transmission process. If a shift mechanism fails, your bike’s transmission will likely have problems.
A motorcycle’s shift mechanism converts the shift lever’s motion into shift slider motion. Most bikes use either a drum-shaped device that activates the sliders with these shift forks or use a spring-loaded cam to get the job done.
Over time, friction and force can wear up and tear up your shifting mechanism. Corrosions from the elements can get in there and complicate your shifting mechanism into a shifty situation.
In some cases, the mechanism gets so worn that you’ll lose the ability to find neutral. After this happens, it’s just a matter of time until your bike fails to shift at all.
If your shifting mechanism return springs wear out to the point that they don’t retract thoroughly, your shifter goes limp, leaving you somewhere between fluctuating shifts and a non-functioning shifter.
Replace your shifting mechanism, and you should be good to go!
2. Shaft or Gear Corrosion
Corroding shafts and gears is one of the myriad problems resulting from an unkempt, sitting motorcycle, and the result could be transmission problems.
Water vapor permeates through the atmospheric vent and into the transmission case.
It descends onto any parts in your transmission box that are unsubmerged by the engine/gearbox oil.
Corroded gears and shafts will run clunky, and you’ll hear all the sounds and experience all the symptoms we talked about in the above section on faulty shifter mechanisms.
When you open up your gearbox to troubleshoot your transmission, keep an eye out for corrosion on the gears and shafts; you should be able to see it.
3. Gears and Bearings Wear
If your gears and bearings wear down, your transmission will develop a tendency to fail. The easiest way to diagnose a failing transmission is by listening to the sounds coming from your motorcycle’s running transmission.
Worn gears make a distinct noise.
Gear lash is what we call the space between the teeth of the gears, and as your gears wear out, your gear lash increases. Extreme gear lash causes a metal clashing sound to clang out of your transmission, especially on shifts, and when you release your clutch lever and engage your clutch.
If your motorcycle’s bearings are the problem, you’ll hear more of a growling noise associated with the spinning transmission. You’ll hear this growl while your clutch lever is extended and the bike’s in neutral if the main shaft bearing is the root of your problem. If it’s a countershaft bearing that’s faulty, the growl grows when the clutch is engaged, and the bike is in gear.
If you hear the gears snarling regardless of whether your clutch is engaged, the damage was done to your clutch hub bearing.
Bikes with chain-driven primaries (Harleys, for example) can make this noise if the chain is too tight, and the tension pulls on the clutch hub bearing. Ensure your chain tensioner is set according to the specs in your bike’s owner’s manual before assuming your clutch hub gear is damaged.
And that brings us to our next section:
4. Chain Tension Set Incorrectly
Motorcycles with chain-driven primaries incorporate a chain system into their transmission. If the chain tension is different from what the manufacturer suggested in the owner’s manual for your motorcycle, it’ll cause transmission issues.
Chain-driven bikes house a drive chain primary that runs from the engine output sprocket to the clutch hub. When you set the chain too tight, it overloads the clutch with resistance, and the result is that same growl sound we mentioned above, accompanied by poor transmission performance.
5. Faulty Throwout Bearing
A worn throwout bearing is another culprit to inspect when troubleshooting transmission problems on a motorcycle.
If your throwout bearing goes faulty, every time you pull the clutch lever in, you’ll hear what they call “bearing howl,” a high-pitched screech caused by a bad bearing being forced to work.
The throwout bearing is a lot smaller than the bearing we discussed earlier, and, therefore, the sound they make is more of a screech or howl than a growl.
6. Bent Shift Forks
Bent shifting forks are another common culprit for motorcycle transmission problems. Your shift forks are the component that connects your transmission’s sliders to the shifting mechanism, and if it gets bent, it forces the correlating slider-gear cluster to get stuck in gear.
At that point, the cluster’s other gear’s dog-to-pockets won’t engage, and shifting into your other gears is useless.
7. Worn Dogs
Bad rider shifting input, worn gear spacers, a faulty shift mechanism, or bent shifting forks can put wear and tear on your dogs, and this will cause transmission problems.
If your dogs and pockets wear down enough, the slider, though still engaging, tends to slip out of gear, especially if you ‘re ripping on the throttle and roasting hard.
Dogs and pockets shouldn’t wear on their own. If your transmission is experiencing slipped shifts and gear pops, you’re not shifting properly, or you have another faulty component in your transmission, probably one of the components mentioned above.
8. Clutch Drag
Clutch drag is another cause of transmission issues on a motorcycle and can result in rigid shifting and gear clashing.
What Is Clutch Drag?
Clutch drag occurs when you depress your clutch lever properly, but the clutch doesn’t disengage completely. It can cause clanking sounds and noticeably rough gear changes.
Repairing a clutch drag could be as simple as swapping your clutch cable with a freshie, but it could also mean replacing the clutch itself. And if corrosion takes hold of your clutch plates, you’re probably bound for clutch drag.
9. Transmission Low on Oil
Whether your bike uses engine oil in your primary or a separate transmission lubricant, the fact is that running an engine with low oil is a sure-fire way to cause transmission issues on a motorcycle.
The easier way to prevent this is to check your oil level regularly, before and after long rides, at the end of your commuter week, etc., and keep up with the make/model-recommended oil service intervals.
If you don’t check your oil and wonder what early symptoms indicate low oil, it starts with startling sounds.
Your bike’s transmission may develop a whine, buzz, or hum that’s new and unusual.
If your transmission roars with a racket or a raucous, you’ve got to check your oil immediately.
Your transmission is a mechanical system of primary metal parts. The oil lubricates your transmission parts to prevent a level of metal-on-metal friction that could cause warped components. Motorcycles usually use a universal oil blend that functions as engine oil and transmission fluid.
If you’re low on oil, those weird sounds you’re hearing, that’s metal-on-metal friction, and it isn’t good for your transmission by any means.
If you’re low on oil, fill her up with fresh clean, owner’s manual recommended blend, and see if the buzzing stops. If you acted fast, it’s probably that easy.
If you hear a clunking sound, you may have a more severe transmission issue, like a worn dog or damaged gear.
More on that in a minute.
10. Bad Rider Input
Improperly timing your clutch disengagements and shifts not only causes problems in real-time but, if not excessively, can also result in clutch damage.
One of the most common reasons motorcycle transmissions have problems is bad rider input on the clutch-lever or foot (or hand) shifter.
We stuck this section at the end to avoid slapping any troubleshooting moto-vets out there with eye-rolling basics. There’s no such thing as being too good at shifting, so let’s call it like it is and hit up a quick review.
How to Properly Shift a Motorcycle Transmission
Follow these steps to shift your motorcycle transmission properly:
- Start the bike in neutral. If the bike you’re preparing to saddle onto wasn’t parked in neutral, pull the clutch lever in all the way and shift into neutral before firing up the motorcycle.
- Shifting into first gear. Don’t throttle up just yet; keep it closed and idling, and yank in your clutch lever and downshift from neutral into first gear to start your journey.
- Roll your throttle up nice and slow while releasing the clutch lever until you find the friction zone, then increase your throttle as you engage your clutch by releasing the clutch lever
- Upshift to higher gears by throttling down as you start to pull your clutch lever in. Once your clutch lever is completely squeezed back, and your clutch is disengaged, set the toes of your boot beneath the foot-controlled shifter and click it up to shift into the next gear. If your RPMs are high enough, you can shift up multiple gears before releasing the clutch lever and reengaging the clutch. Still, I suggest engaging the clutch and rev-matching your RPMs between every upshift, especially when new to riding. Once you’re in the appropriate gear, throttle up.
- Downshift to lower gears by throttling down until the throttle is closed and yanking in the clutch. Place the tip of your boot-sole on top of the shifter and click it down. You’ll feel it when the gear engages.
- When slowing to a stop, repeat the above action, engine breaking to rev match, dropping your RPMs more and more on each downshift until you’re in first gear.
- Excessive redlining will cause transmission problems on your motorcycle down the road. If you accelerate in a low gear past the point where you should’ve shifted, your RPMs will skyrocket, eventually passing the red-marked RPM numbers of your gauge. This is called redlining, and it will absolutely wear out your transmission.