Triumph Bonneville Problems: 6 Known Issues (Explained)

When someone says modern-classic, it’s the Triumph Bonneville that comes to mind.

From its stellar handling and world-class handling to its sleek, minimalistic style, the Triumph Bonneville seems so to have it all.

Bonneville owners rant and rave about its upsides, but what do they say about its flaws?

As with every well-built machine, there have been some owner incident reports.

Whether you’re in the market for a Bonneville or the proud owner of one, learning what other owners did to rectify these common complaints could save you some time and money.

Let’s get into it!

1. Downshifting Problems

Comb the Triumph forums, and you hear quite a bit of chatter regarding Bonneville’s downshifting problem. That said, it seems like, for every owner who’s experienced it, there’s another owner who’s never heard of it.

We dug a little deeper and narrowed down the common denominators.

Improper Shifting

Let’s go ahead and get this out of the way. The Bonneville is iconic, partially due to its unique rideability; some of the riders who experienced difficulty downshifting were at the apex of a learning curve.

It’s not uncommon for a motorcycle transmission to get stuck in high gear if the downshifting is rushed on it at a stoplight.

Downshifting gracefully requires subtle shifting through the gears. Release the Clutch just slightly to engine-brake between each gear to slow your RPMs to the appropriate rate before entering the lower gear.

Each bike is different, and learning the sweet spots for shifting cones with experience.

Also, some riders are inclined to keep the bike in first gear when stopped, with the clutch engaged to keep the bike running.

Idling in gear with the clutch lever pulled in can generate a clutch-drag that causes gear selection issues.

Engine braking between each downshift on your way to a stop and putting the bike in neutral while idling is the best way to maintain smooth downshifts on any motorcycle.

Left-Side Bike Damage

Unfortunately,  many of the claims about faulty downshifting pertained to bikes that had dropped on the left side.

The shifter on the Bonneville is rather rigid, and while the footpegs retract to keep from sustaining damage, this leaves the shifter to take the brunt of the fall.

Many of the downshifting issues we’ve encountered resulted from trivial damage to critical parts inside the shifter. 

For example, there’s a spring in the shifter that keeps its arm against the shifter detent. When functioning properly, the detent engages in preparing for the next shift.
If this return spring is broken, the detent spins without engaging, and the shifter shaft would not be able to rotate the shifter drum.


Here is a link to our article that talks on 5 Most-Common Problems With Triumph Thunderbird


Other Parts that may need replacement after a Triumph Bonneville is dropped on its left side:

  1.  The two selector springs.
  2. The shifter detent roller assembly (and its spring, mentioned earlier).
  3. Pivot plate.
  4. Clutch nut.
  5. Spring washer.
  6. Clutch cover gasket.

One popular safeguard we’ve been suggested is to install a dirt bike shifter. On a dirt bike shift lever, the end folds back when the bike drops, yielding to the fall to prevent damage.

We’ve also seen threads suggesting a small Honda bike shifter that, when in place, lets the handlebar take the hit rather than the shifter.

2. Starting Problems

Triumph Bonnevilles have been around for years; used Bonneville’s aren’t hard to come by, but just like with any used vehicle, it’s hard to know what kind of maintenance was done the bike before you took it by the handlebars and made it your own.

More often than not, the culprit for starting problems is a bad battery.

 Signs of a Dead Battery or Draining Issue:

  • Bike not starting
  • Corrosion on battery contacts
  • Unresponsive dash lights
  • Starter clicking rapidly
  • The bike only starts when cold/hot.

Battery drain issues aren’t a Triumph exclusive by any means— compared to a car battery, motorcycle batteries are small.

Modern CPU-related bike technologies put more strain on the battery than the older models, so battery inspection is more crucial than ever.

On newer models, Triumph has made an effort to upgrade its batteries.

Still, all batteries wear out eventually, so it’s important to make battery inspection and replacement, if necessary, part of routine maintenance on any vehicle.

The first thing to look into when experiencing battery issues is making sure the battery terminals are screwed on tight; bikes rattle and screws shake loose, and weak battery connection can cause electrical failure on a whole bike, but it’s nothing a few 90-degree turns on the battery terminal can’t fix.

If replacing the battery doesn’t prevent dead battery symptoms, a bad regulator/rectifier can cause problems that seem to be coming from the battery.

We’ve also met a few instances where the culprit was a worn ignition switch.

Just like on any bike, it’s important to inspect and maintain your Bonneville in adherence to the user manual, as the best offense against starting problems is a good defense.

3. Loud Squealing Brake Pads

A few Triumph Bonneville owners have complained about loud squealing or screeching noise when braking.

Because the brake pads on a motorcycle are more exposed than that on a car, they’re prone to collecting dirt and haveing debris lodged into them.

The number one culprit for squeaky brakes on a motorcycle is debris getting stuck between the pads and the disk.

If there is dust in the brake pads, simply cleaning out the lodged dirt should do the trick of eliminating the sequel.

Break squeals could also be the result of a bent of the damaged rotor.

If brake rotors are warped, riders can expect to hear sounds that range from a low-pitched squeak to a heavy thumping noise upon applying their breaks.

This is usually the situation for bike-owners who don’t keep up with brake pad changes, as worn pads result in the metal to metal contact.

If brake pads aren’t being changed regularly, rotors can incur damage that makes them uneven and causes warping.

For preventing rotor surface wear, the best offense is a good defense.

Make sure you’re changing your brake pads regularly in adherence to your bike’s maintenance schedule. Nothing reduces a rotor’s lifespan quicker than riding on worn-out brake pads— keep those brake pads fresh and fresh and clean!

4. Exhaust Popping On Deceleration

Exhaust popping, or backfiring, is a symptom of a rich fuel mix.

Backfiring is what we call the popping that shoots from the exhaust during deceleration.

Some owners don’t mind it, while others can’t stand it. Regardless of preference, it indicates an issue with too much fuel entering the combustion chamber.

On the modern Bonnevilles, fuel injection is regulated by the bike’s CPU.

If the CPU allows an excess of fuel into the exhaust header, the unused fuel burns off during combustion. The burning off of that extra fuel causes the backfiring that creates the loud popping noise.

Owners should regularly inspect fuel and air systems for leaks. During routine service maintenance, the mechanic will read your Bonneville’s CPU. Any variations to the air: fuel ratio can be adjusted with a quick remapping, yet another case closed by good old-fashioned routine maintenance and inspection.

5. Cam Cover Gasket Oil Leak

Although not particularly widespread, the cam cover oil leak is a problem a handful of Triumph Bonneville owners have faced.

At first, the oil appears to be leaking from the valve cover or its gasket. but further, inspection usually proves that this isn’t the case

While the gaskets do wear out, hence their routine replacement around 12,000 miles, more often than not, the gasket isn’t actually to blame— it’s the washers used to bolt down the cams that are leaking.

The strength of the factory washers on many of the leaking Bonnevilles has reportedly dissipated much earlier than the manufacturer anticipated, weakening their torque onto the cams, and, eventually, the washer starts to weep oil. Replacing those washers often seals the leak.

In addition to upgrading those rubber washers, pop opened the cam cover and cleaned any oil on the head surface and the rubber gasket.

Some will recommend lightly oiling the gasket before installing, while others suggest assembling it dry to prevent oil between the gasket and the cover.

Tighten those four bolts with your new rubber washers. They need to be snug but not overly tight, or they’ll strip and could leak all over again.

Whether the issue is the gasket or the washers, the dealership can fix any of the Triumph Bonneville’s oil leaks under warranty if the warranty is still valid.

6. Corrosion Issues

Here’s a section useful to any motorcycle owner, especially those who live in rainy areas or next to a beach.

Oceanside areas tend to cause more corrosion because of the salty air and ocean water.

Like on any bike in these areas, a Triumph Bonneville’s rusting ordinarily starts at the wheels, exhausts, and around any bolts exposed on the bike.

The most significant contributor to corrosion on a bike tends to be where and how it is stored.

For example, storing a Bonneville in a garage full of pool products and paint can is more prone to causing corrosion.

Using metal polish on the bike’s rusted areas is one way to deal with corrosion once it’s taken place,  and keeping the bike lubricated with WD-40, ACF 50, or corrosion block is a good way to play defense.

Corrosion and rust are not significantly dangerous, but since Bonneville is such a good-looking bike keeping it shiny makes for s happier rider.

General Pros And Cons For The Triumph Bonneville


“Bobbers” are typically one of the best bikes to ride out there. Not only does the Bonneville engine sound like a well-made machine, but it also delivers a classically comfortable ride.

The Triumph Bonneville is very flexible in customization with multiple choices for accessories. This also makes it easy to find parts for the bike, whether aftermarket parts or stock.

The iconic Bonneville features a classic design with modern technologies such as traction control, ABS, riding modes, and torque-assist clutch. It’s great for everyday riding and highway cruising with maximum power at 40.5kW at 5 900rpm and torque at a steady 80Nm at 3 230rpm.

The Triumph Bonneville T100 is much lighter than the T120 model, but both models offer a responsive ride for both back-roads and normal roads.


  • Downshifting Problems
  • Starting Problems
  • Loud Squealing Brake Pads
  • Exhaust Popping On Deceleration
  • Cam Cover Gasket Oil Leak
  • Corrosion Issues

What Do the Reviews Say?

It’s a more mature Bonnie for riders who don’t mind taking the scenic route. The 1200cc engine is tuned for maximum comfort and high-torque practicality.

“As long as you’re above 2000 RPMs, you don’t need to consider changing down to accelerate with ease.”

“The salty old guy in me wanted to hate this bike because of the name, but the new 1200cc engine and unique mono-shock chassis on this bike are just SO nice. I never had a choice but to love it.”

What Is The Resale Value On The Triumph Bonnevilles?

Bike Model Year Mileage(miles) Price
Bonneville SE 2009 16,300 5,000
Bonneville T100 2010 12,500 5,300
Bonneville T100 2011 21,818 4,500
Bonneville T100 2012 10,000 5,000
Bonneville T100 2013 14,629 6,695
Bonneville T120 2018 2,241 9,600
Bonneville T100 2019 515 7,300

NB: The above prices may vary according to the bike model and mileage, as well as your location.


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ⓘ  The information in this article is based on data from National Highway Traffic Safety Administration (NHTSA) recall reports, consumer complaints submitted to the NHTSA, reliability ratings from J.D. Power, auto review and rating sites such as Edmunds, specialist forums, etc. We analyzed this data to provide insights into the best and worst years for these vehicle models.