When a motorcycle speedometer stops working, the cause is usually one of four things: a broken or disconnected cable, a speedometer drive at the wheel that’s no longer engaged (often right after a tyre change), a faulty or dirty speed sensor, or a wiring or fuse fault. If it reads wrong rather than dead, look at recent changes to tyre size or sprockets. Work from the wheel up to the gauge, and until it’s fixed, a phone running a GPS speedometer on a solid mount will show your true speed, because satellites don’t care about cables or sensors.
Your service manual has the exact specifications for your model. This guide gets you to the right page.
What does the symptom tell you? #
| Symptom | Likely cause | First thing to check |
|---|---|---|
| Needle and odometer both dead (cable bike) | Broken or disconnected cable, or failed drive | Cable ends, then spin the wheel |
| Odometer counts but needle is dead | Fault inside the gauge | Gauge repair or replacement |
| Needle bounces or swings | Dry, kinked or damaged cable, worn drive gear | Lube or replace, check routing |
| Stopped right after a front wheel or tyre change | Drive tabs not engaged, or sensor unplugged | How the wheel went back in |
| Digital speed reads 0 while riding | Sensor, wiring, fuse or air-gap fault | Connector, sensor tip, air gap, fuse |
| Speedometer dead and the ABS light on | Wheel-speed sensor shared with the ABS | The same sensor; a shop can read fault codes |
| Whole dashboard dark | Fuse, dash connector or battery voltage | Fuses and connectors |
| Reads wrong after a sprocket change | Sensor on the gearbox output | Recalibrate or correct |
| Reads wrong after a tyre size change | Rolling circumference changed | Recalculate and correct |
How do you fix a cable-driven speedometer? #
Older bikes and many simple modern ones drive the speedometer with a spinning inner cable from a small gearbox at the front wheel, and the odometer runs off the same cable, which is why both die together. With the bike on a stand:
- Disconnect the cable at the gauge. It’s usually held by a knurled nut.
- Spin the front wheel and watch the square tip of the inner cable. If it turns, the cable and drive are fine and the fault is in the gauge.
- If it doesn’t turn, disconnect the cable at the wheel end and spin again. If the drive’s socket turns, the cable is broken. If it doesn’t, the drive is worn or not engaged.
- Pull the inner cable out. If it comes out in two pieces, that’s your answer. Look for fraying and kinks too.
- Lubricate or replace. Use a cable lubricant along the inner cable but keep it off the top few inches, because oil that creeps into the gauge causes problems of its own.
- Check the routing. Tight bends make the needle bounce, and a cable near the exhaust can cook.
After a tyre change: on many cable bikes the drive unit has tabs that must sit in slots on the hub, and the unit has to locate against a stop on the fork leg before the axle is tightened. If the wheel went back in with the drive misaligned, the tabs get crushed or simply don’t turn. It’s one of the most common reasons a speedometer dies right after new rubber.
How do you fix an electronic speedometer? #
Most newer bikes read speed from a sensor: a magnetic pickup next to a toothed ring or the rotor bolts, a sensor on the gearbox output, or the ABS wheel-speed sensor.
- Connector. Check it’s plugged in, especially after wheel or fork work, and look for corrosion on the pins.
- Sensor tip. Magnetic sensors collect metal filings and road grime. Clean the tip.
- Air gap. The gap between sensor and ring has a specification in your manual. A bent bracket or a spill can open it up.
- Tone ring. Look for missing or damaged teeth.
- Fuse and wiring. Check the fuse, and look for chafed wires where the loom passes the steering head.
- Warning lights. If the ABS or traction-control light is on with the speedometer dead, suspect the wheel-speed sensor, and have it checked soon, since the ABS may not work while the fault is present.
Why does it read wrong after a sprocket or tyre change? #
Where the sensor sits decides what affects the reading. With a sensor at the front wheel, sprocket changes don’t matter but tyre size does. With a sensor on the gearbox output, sprocket changes do, because the bike still assumes stock gearing. The error ratio is (new front teeth ÷ new rear teeth) ÷ (old front ÷ old rear).
| Change | Ratio | Effect on the speedometer |
|---|---|---|
| 15/45 to 16/45 (one tooth up front) | 1.067 | Reads about 6% low: indicated 60 is really 64 |
| 15/45 to 14/45 (one tooth down front) | 0.933 | Reads about 7% high: indicated 60 is really 56 |
| 15/45 to 15/42 (three teeth off the rear) | 1.071 | Reads about 7% low |
Reading low is the dangerous direction, because you’re going faster than it shows, and your odometer under-counts too. The fixes: return to stock gearing, ask a dealer whether your model can be reprogrammed, fit a plug-in speedometer correction module (made for many models), or on cable bikes fit a drive unit with a different ratio. For measuring an error that isn’t this dramatic, see motorcycle speedometer vs GPS: why your bike reads high.
Is it legal to ride with a broken speedometer? #
That depends on where you live. Many countries and states treat a working speedometer as part of a roadworthy vehicle, and it may be checked at inspection or draw a ticket. A phone app helps you keep to the limit, but don’t assume it counts as a legal substitute for the bike’s own instrument. Check the rules where you ride and get the gauge fixed promptly. Whatever you use, you’re responsible for the speed you ride at.
How do you use a GPS speedometer as a check or a stopgap? #
A GPS speedometer measures speed over the ground and ignores cables, sensors, tyres and sprockets.
Checking a repair #
You can’t safely compare a phone and the dash while riding, so record the ride instead:
- Open Speedometer GPS before you ride, wait for the accuracy indicator to show a good fix, and press Start.
- Put the phone in a jacket pocket or leave it in its mount.
- On a straight, quiet road, hold a steady indicated speed, say 50 mph, for 15 seconds, then 70 mph for 15 seconds.
- At home, save the trip and open its speed chart. The flat sections show your true speed at each indicated speed.
Riding home on a phone #
- Pick the phone. Apple advises against attaching an iPhone to motorcycles with high-power or high-volume engines, because the vibration can degrade the camera’s stabilisation and autofocus, and recommends a vibration-dampening mount on mopeds and scooters. An old spare phone is sensible on a big bike.
- Mount it firmly in a locking mount with a damper, where it doesn’t block your mirrors or warning lights. A spring clamp that lets go at speed is a hazard to the rider behind you.
- Give it power from a fused USB socket if the ride is long, and keep rain out with a waterproof mount.
- Set everything up while parked: units, a speed alarm for the roads you’ll ride, and keep-screen-on (on by default). Wait 20 or 30 seconds in the open for a good fix.
- Don’t touch it on the move, and keep your eyes on the road. Let the alarm do the work: when you pass the limit, the whole readout turns red and the phone buzzes and beeps every 10 seconds until you slow. You’ll catch the red in peripheral vision even if you can’t hear the beep through a helmet.
How accurate is GPS compared with the bike’s gauge? #
At a steady speed with a clear sky, a phone’s GPS speed is usually within a couple of km/h of your true speed. Your bike’s speedometer, when it worked, probably read higher: motorcycles fall under UN Regulation No. 39 in the markets that apply it, which says a speedometer must never read low and may read up to 10% plus 4 km/h high. So if you cruised at an indicated 110 km/h, the phone might show 104 or 105 at the same real speed. That’s the phone being honest, not a reason to ride faster.
The phone is weaker than the gauge it’s replacing in three places:
- Hard acceleration and braking. GPS speed arrives once a second and is averaged, so it trails by a second or two; why GPS speed lags your gauge explains it.
- Tunnels, dense trees and deep valleys, where it loses the satellites. Speedometer GPS drops to 0 after five seconds without a fix rather than freezing on an old speed; GPS in tunnels and cities covers what to do.
- Track days. One reading a second with smoothing is too slow for lap timing or braking points.
What about the odometer and service intervals? #
If the odometer stopped along with the speedometer, the miles you ride now aren’t being counted, which matters for service intervals, warranty records and resale. Keep a log. Speedometer GPS saves each ride with its distance, and the Trips screen adds up to 100 saved trips into a lifetime odometer, so you can add the total to your service record when the gauge is fixed. At road speeds its distance is close. It ignores steps under 5 metres between one-second fixes, so filtering through traffic below about 18 km/h (11 mph) under-counts a little; for a service log that doesn’t matter.
Frequently asked questions #
Can I use my phone as a speedometer on a motorcycle? #
As a temporary measure, yes. Mount it firmly in a damped mount, power it from the bike, set it up before riding and don’t touch it on the move. Check local rules, since many places require the bike’s own speedometer to work.
Is a GPS app more accurate than a motorcycle speedometer? #
At a steady speed with a good signal, usually yes, because bike speedometers are designed to read high and GPS isn’t affected by tyres or sprockets. The bike’s gauge is better under hard acceleration and in tunnels.
Why did my speedometer stop working after I changed my front tyre? #
Usually the drive or sensor wasn’t reinstalled correctly. On cable bikes, the drive’s tabs have to engage slots in the hub and the unit has to sit against its stop. On sensor bikes, check the connector and the air gap.
Does a broken speedometer cable stop the odometer? #
On cable-driven bikes, yes. The odometer is driven by the same cable, so both stop together. Log your distance with a GPS app until it’s fixed.
Why does my speedometer needle bounce? #
On cable speedometers it’s usually a dry, kinked or damaged cable, or one routed through a tight bend. Clean and lubricate the inner cable (keeping lube off the top end), check the routing, and replace it if it’s frayed.