The Honda VT125C, or the Shadow 125, is a cruiser motorcycle manufactured by Honda between 1999 and 2007.
Although the VT125 only had a V2, four-stroke 125cc motor, it looks like one of its beefier Shadow siblings.
The unique design of this small-displacement America-medium-cruiser-inspired little ripper put out 15 horsepower at 11,000 RPMs for a max speed of 69 mph. Since only used models are available, you’re probably wondering about the common problems with the Honda VT125?
We dove into the forums and brought you the inside scoop on the slightest Shadow!
1. Lack of Power Leads to Baffle Removal Leads to Exhaust Problems
All over the VT125 forums, you hear stories like this:
A kid’s bike was running fine, right—so good that they decided to upgrade their exhaust into something that’ll shake the leaves off the ground and wake the neighbors.
The overconfident moto-meddler takes the vacuum system apart and removes the baffles or cuts his pipes off to try to “retune” their Shadow, and now they’re experiencing a loss of power.
The meddling kid can’t figure out why his bike is losing power during long rides and sells it to you.
You experience a power loss, so you pull off your exhaust to compare it to spec only to find out the 0.2 opening on the front header is now 0.6, and the 0.15 air intake is blown to a 0.3 since the previous owner removed the baffles.
All they wanted was a unique sounding bike, and that’s exactly what they gave you; the engine sound ranges from a tinny taunting tone to a wild roar that sounds like it’s on the verge of dropping its valves.
Or maybe it sounds standard one second, then sounds like it’s revving high the next, but not in a good way.
And finally, you’ll notice a ticking sound coming straight from the engine, and when you ride, you see your bike going in and out of losing power.
The simple fact is that the Honda Shadow VT125C might look like its older siblings; it’s probably the beefiest 125 of all time and certainly the most American-looking.
That said, no aftermarket pipes or dyno jet tuner will change any 125 into a 500, but the 125 Shadow already has a few things working against it.
- The VT125’s beefy body is heavy.
- It’s the same body the 250 uses, although the 125 is half as powerful.
- The VT125 is underpowered even with a factory tune—making it louder by meddling with your vacuum and exhaust systems will only make it less powerful.
We’ve included this section specifically because the VT125 is a great starter bike if what you’re looking for is a small motor hidden in a stylish, medium cruiser package. But the engine specs aren’t following anyone.
Honda eventually discontinued the VT125, but there are a ton available used—it’s a popular choice for learners.
The loss of power results from an affected air-fuel ratio at the hands of the previous owner, probably from meddling with the exhaust or the air intake vacuum systems to make it louder or boost its specs.
If you bought a used Honda VT125 and you think the previous owner tampered with your exhaust, take it to the dealership and have them investigate and retune your ai-fuel ratio.
Or, you can try a few of these tips:
- Put new plugs in and put the original exhaust back on, and I hope you haven’t burned a valve out.
- The previous owner probably wanted the VT125 to sound ‘cool’ and removed the baffles.
- If you do replace your exhaust or intake systems, don’t up-jet or retune at all when you fit on the new exhaust or you risk running lean and overheating.
- Check your valve clearance. If the previous owner made a mess tampering with your vacuum, chances are they weren’t capable of retuning things, and your valves have gone massively out of spec; hence the ticking/tapping sound I referenced in the exhilarating reenactment above.
- Seriously, though. Valves out of spec are probably the cause of any sudden loss of power.
- Also, try running a compression test on both pots while the motor is still hot.
You might have to take the heads off and see what’s going on with the valves and their seats, and without a pretty extensive home-mechanic setup, you may have to go to a shop for that.
If the previous owner had wide-open pipes on your VT125 for a while without ever re-jetting the carbs, it’s pretty likely that, in addition to the valves being wacky now, you’re also running too lean. Running lean is concerning on a lil 125 motor that revs to 11-12k.
As to pipes themselves:
- Is there potential for a power gain by opening things up? A tiny power gain, sure if you replace your pipes with aftermarket that are fabbed to fit your bike, is the ideal length, or tuned 2-1, but only if you want to spend a week setting up the fueling on a dyno.
- An open-air filter might also change the airflow and fueling. Still, you’ll have to spend time retuning, rejecting, and taking extra precautions to ensure no debris enters your engine for a nominal gain in throttle response.
- But for the most part, back pressure on any four-stroke motor is a myth. Flow velocity is the crucial thing in exhaust system design on the VT125.
To be clear, we’ve got nothing against people wanting to up-tune a 125 as long as they accept its high risk for low reward.
So, in summary, the 125 is what it is, an entry-level motorcycle engine hidden in a beefy midsize cruiser. You will undoubtedly outgrow it, and when that happens, you can’t just slap a new part on and expect it to run like a 500.
2. Tail Light Stops Working If Replaced (Solved)
The VT125 is a beginner motorcycle, and it gets the job done while saving you from looking like a gorilla riding a football like some of the other 125s on the market.
One common accident that happens regularly to new riders is dropping their bike, often while at a standstill or at slow speeds when balancing becomes more difficult.
Dropping a bike at slow speeds causes primarily minimal damage, but it’s not uncommon for a flailing foot to, say, snap off a tail light, for example.
That said, a few VT125 owners I encountered in the forums claimed that a simple tail light installation font of the VT125 could be a little more confusing than on other models they’ve worked with.
One rider puts it like this:
I unplugged the three wires from under the seat (1 brown wire and two green-yellow wires).
I did what needed to be done, and now when I plugged the wires back in and turned the ignition on, the bulb lit up. Then I pressed the brake lever to see if the brake light worked, but the bulb didn’t work anymore after pressing the lever. I tried reconnecting the wires, but nothing. Then I noticed nothing but the front light working. The dash, turn signals, odometer, and everything else does not show any signs of life.
I think I blew a fuse, but could anyone tell me how that would be possible since I connected all the wires the way they were before.
Ok, so here’s the deal.
It sounds like this rider had a break in their brake light wire, but not the running light wire, which was grounding out.
If you’re experiencing something similar, check that the whole assembly is still bolted to the mini Shadow’s fender.
If the assembly shifts onto fender rust, the tail light won’t ignite until the rust is cleaned.
- There should be one green ground wire, one yellow brake light wire, and one brown tail light wire. The yellow wire looks green to some people, especially in the sun or in certain garage lights, and some riders reverse the green and yellow wires. This not only prevents the light bulb from igniting, but it could also blow a fuse.
- I googled the wire color codes, and for Honda, it says the following:
- Tail – brown with white stripe
- Brake – green with red or yellow stripe
- Ground – solid green
In summary, if you confuse the green with yellow for the solid green wire, you connect your ground to the brake light wire, which can cause a fuse to blow.
The wire will have to be switched back, and you’ll have to replace any blown fuses.
3. Bike Won’t Start (Solved)
One of the most frustrating experiences for a rider, especially one excited to start learning on the used VT125C they just scored, is when the bike doesn’t start.
This isn’t due to any fault of Honda, mind you, but it happens often enough we figured to include it.
Unfortunately, used beginner bikes often get sold with bad batteries. A bad battery can evade detection by using the last of its juice to start up when you’re test riding the mini Shadow, but once you get it home, nothing happens, as the test ride ignition killed off the last of the battery’s juice.
Let’s look at a few symptoms of a dead battery on a Honda VT125C:
- Running lights are off or dim
- Pressing the ignition switch only results in a clicking sound
- The starter tries to crank over a few times, then gives up, and nothing happens
So now you know it’s dead, but not if it’s bad; it might just need a charge.
Next step, how does your VT125’s battery look?
- Broken terminals
- Battery fluid leaks
- Breaks split, or bulges in the battery case
If everything looks ok, check the voltage with a digital voltmeter or run it by a motorcycle, mechanic, or auto parts store, and they’ll help you out.
General Pros and Cons for Honda VT125s
Here are some pros and cons of the Honda VT125:
- Great learner motorcycle
- Small displacement motor in a medium-cruiser makes it look like you’re riding a full-sized Shadow
- It lasts a long time when well-maintained
- Lack of Power Leads to Baffle Removal Leads to Exhaust Problems
- Tail Light Stops Working If Replaced (Solved)
- Bike Won’t Start (Solved)
What Do the Reviews Say?
If you’re ultimately yearning for a mammoth cruiser but have yet to perfect the art of riding one, the Honda VT125C Shadow is the bike for you.
The littlest Shadow looks the part, is beautifully finished, very reliable and is relatively gentle and forgiving for the novice rider. The Honda VT125C Shadow is a bit lardy, and rather expensive, but an excellent entry level machine for custom fans.
Wide, plush seat, forward footrests and high bars make for laidback riding, California style on the Honda VT125C Shadow. Brakes and suspension are ample; nothing’s too extreme.
What’s the Resale Value of a Honda VT125?