Since as far back as the 1960s, Honda has been making Scramblers, a Cafe racer-inspired motorcycle with knobby, off-road tires.
Honda’s line of Scramblers was the predecessor to modern dual-sport motorcycles. However, they weren’t equipped for the adventure bike riding of today’s hobbyists. Honda launched its Scramblers before there was even such a thing as a dirt bike.
Vintage Honda Scramblers are appreciated for how ahead of their time they were, and as such, they’re a hot commodity for moto-collectors, but what are the common problems with Honda Scramblers?
In this article, we’ll take a crack at troubleshooting some of the issues that have plagued fans of these vintage classics.
1. Regulator/Rectifier Failure
The Regulator/Rectifier on an old Honda Scrambler is bound to need replacement multiple times throughout the bike’s life, especially on a Vintage model.
The Regulator/Rectifier is a critical component in a Scrambler’s charging system. First, we’ll look at how the part works, and then we’ll cover some Scrambler R/R troubleshooting tips.
How a Regulator/Rectifier Works on a Honda Scrambler
Any bike with a battery, including the Honda Scrambler, uses a circuit system to charge the battery during operation.
A key charging system component is the Regulator/Rectifier.
The Regulator/Rectifier on a Honda Scrambler rectifies the AC power produced by the stator coil by converting it to DC power, using it to charge the battery.
The Regulator/Rectifier also regulates the power output—the R/R also prevents your battery from incurring damage or exploding by keeping the power output within the 14.5-volt range required by your battery.
Causes of Regulator/Rectifier Failure on a Honda Scrambler
There is a multitude of possible contributors to Regulator/Rectifier failure, the most common being heat.
Until 15-20 or so years ago, Honda’s Regulator/Rectifiers weren’t equipped to handle the heat generated by their four-valve power-house engines.
Some blame the integrity of the part itself. In contrast, others point to Honda’s R/R placement on the Scrambler, theorizing that the location puts the piece in a heat-concentrated area without ample airflow.
A Regulator/Rectifier that overheats regularly is bound to fail, eventually. Considering that most vintage Scramblers are upwards of 50 years old, it’s no wonder why the part needs to be replaced so frequently.
Another possible culprit is a malfunctioning battery, whether at the hands-on unreliable connections or because of the battery being old or weak.
Symptoms of a Failing Regulator/Rectifier on a Honda Scrambler
There are two general ways that a Regulator/Rectifier fails, including on a Scrambler.
If the diode burns out, your Scrambler’s battery will drain, causing all the usual lousy battery symptoms, like:
- Dimming headlights
- Fluctuating readings
- Hard starting
- Scrambler won’t start at all.
At the sign of the symptoms mentioned above, the first thing to do is grab a voltmeter and check your battery. If the voltage reads less than 13 volts, your battery is draining and hasn’t been replenished by your Scrambler’s Regulator/Rectifier the way that it should be.
The second common way a Regulator/Rectifier fails on a Honda Scrambler is if the shunt regulator wears out. This is the component that monitors and moderates the motorcycle’s volt level. Without this capability, the bike’s battery will overcharge, die, or explode.
Just like you used that voltmeter earlier to detect an undercharge, you can use it to diagnose an overcharged battery as well.
The ideal reading for a Honda Scrambler’s battery is 14.5 volts. If your voltmeter reading hits 17 volts or over, it’s possible that your Regulator/Rectifier isn’t converting your extra power as it should, and your battery has overcharged.
Another symptom of an overcharged battery on a Honda Scrambler is your headlights getting brighter than average, getting more and more luminous until your headlights die.
How to Test Your Honda Scrambler’s Regulator/Rectifier
Follow these steps to test your Honda Scrambler’s Regulator/Rectifier:
- Disconnect your Honda Scrambler’s wires.
- Flip your multimeter to the diode setting.
- To check your rectifier, insert the positive lead into your Scrambler’s positive diode and inspect the multimeter’s negative lead to the Scrambler’s stator inputs. There should be no readings on your multimeter at this point.
- Connect the Scrambler’s positive diode to your multimeter’s negative lead and your positive lead to the Scrambler’s stator. The meter should read, but the reading doesn’t matter just yet.
- Repeat for the negative diode by connecting the meter’s positive lead to Scrambler’s negative diode and the negative lead to Scrambler’s stator input. Once again, the meter shouldn’t show any reads when you connect the positive lead and stator inputs.
- Now, check the Scrambler’s regulator by hooking the meter leads up to your Honda Scrambler’s battery while it’s idling. You want a reading lower than 14.5 volts but higher than 13.5 volts. If the reading is higher, this means the battery is overcharged. If it’s lower, your battery isn’t getting the charge it needs. Either way, chances are good that you need to replace your Regulator/Rectifier.
Luckily, replacing your R/R is a straightforward job for any decent home mechanic. If not, Honda mechanics are well-versed in the problems and solutions of their vintage Scrambler model’s failing Regulator/Rectifiers.
2. Electrical System Corrosion
Electrical issues are a common complaint about vintage Honda Scramblers. Everything wears out eventually, and electrical components on an old Honda Scrambler can corrode due to water or sun damage, vibration, or just plain old age.
Finding the root of the problem is the first step towards finding the solution—let’s look at a Honda Scramblers’ essential electrical components to troubleshoot for the weak spot.
Inspect Your Honda Scrambler’s Battery
The battery is the first thing you should check if your Honda Scrambler is having electrical problems. First thing’s first, check if your Honda’s Scrambler’s battery is fully charged:
The battery of a Honda Scrambler should hold a minimum of 12 volts when the ignition, lights, and power are off. If your Scrambler’s battery holds less than 12 volts, charge your battery and test it again. If it’s still under 12 volts, your Scrambler’s battery is bad.
A battery with a low charge will struggle to zap your Scrambler’s starter with enough juice to start the bike’s engine. If your battery is charged and healthy, it could be something as simple as ensuring your battery terminal cables are screwed down onto your battery.
Loose terminal cables weaken the battery’s output, sometimes to the point of causing intermittent power loss while riding; tighten those suckers up well!
We already covered Regulator/Rectifier in the above section, but if your battery isn’t holding a charge, or if it’s more than 15 volts, refer to that section and inspect your Honda Scrambler’s Regulator/Rectifier next.
Inspect Your Scrambler’s Main Fuses
Your Honda Scrambler’s wiring harness is powered without its main fuse. That said, your Scrambler doesn’t have to be powerless for the main fuse to be the issue; a faulty primary fuse connection will cause the motorcycle to dip in performance.
And it might not be that your main fuse is blown and needs replacement. The Honda Scrambler’s engine vibration may have just loosened it. Or, if you set your Scrambler’s knobby tires down in the dirt to some off-road ripping, you may have just shaken the fuse a little loose.
That said, enough vibration can short your fuse dead—make a habit of carrying backup fuses, especially during off-road Scrambler adventures.
If you replaced your fuse multiple times and your fuses keep blowing, read on; you probably have an issue elsewhere in your Scrambler’s electronic system.
Inspect Your Scrambler’s Ground Wires
One of the more common issues on vintage Scramblers is faulty ground wires, an issue on any old motorcycle at the hands of corrosion associated with aging.
The first sign of faulty ground wires on a Honda Scrambler is flickering lights. Eventually, your loyal little Scrambler will experience issues starting.
Consult the service manual of your specific year and model of Honda Scrambler to learn the locations of your bike’s ground wires.
If your Honda Scrambler is experiencing electrical issues, inspect your ground wires. Replacing any faulty or corroded ground wires is a relatively inexpensive fix.
Inspect Your Scrambler’s Stator
If you’re having charging problems on your Honda Scrambler, and you’ve ensured your battery and Regulator/Rectifier are both good, inspecting your stator is the next step.
The stator charges your battery by redirecting the extra power generated by the bike’s engine and electronic system.
If your stator is bad, your battery’s charge, and therefore performance, will dive during operation.
How to Know if Your Stator is Bad on a Honda Scrambler:
- Unplug your Regulator/Rectifier from your stator.
- Flick your multimeter into the Ohms setting and test the terminals on the stator by linking A to B with the positive-negative multimeter leads. Your reading should be 1 Ohm.
- Now, the same way, test again by linking B to C. Your multimeter reading should be 1 Ohm.
- Test once more linking C to A. 1 Ohm. If this or any previous readings were higher than 1.5 Ohms, you might have a faulty stator on your hands.
- Now, reconnect your Regulator/Rectifier and your stator and switch that multimeter to test for AC.
- Start your Honda Scrambler.
- Perform all the same tests (A to B, B to C, C to A). You want a reading of 16 volts. If your output is lower than 15 volts, you might have a faulty Stator.
3. Dried Out Slider Diaphragms and Intake Manifolds
The Honda Scramblers, namely the CL350, had a state-of-the-art fuel system for its day.
It stocked two Keihin Constant Velocity carbs and ran them straight through a single petcock from the fuel tank.
The throttle cable extending from your throttle is what yanks on your carb, and on the Honda CL350 Scrambler, that cable is a 1-into-2 split. The wires have to be synced for accurate throttle progression and speed.
Ok, now that you’ve got that picture in your head, you’ll appreciate why dried-out fuel system components are an issue.
See, the slide diaphragms and intake manifolds of a Honda Scrambler have a habit of drying out, and this causes tuning issues. It’s standard practice to rebuild the carb of a vintage bike like a CL350 Scrambler, and when you do, replacing the slides, and the intakes will keep this issue in the bud before it starts.
What Are the Pros and Cons of a Honda Scrambler?
Here are some pros and cons of the Honda Scramber:
Here are some of the selling points of the Scrambler:
- Decent Motor
- Aluminum Crankcase Split Horizontally to Contain Oil in Leakproof Fashion
- Unswept Exhaust Pipes
- Vintage Scrambler Style
- Sporty Chassis
- Fun to Ride
- Collector’s Item
Here are some shortcomings of the Scrambler:
- Regulator/Rectifier Failure
- Electrical System Corrosion
- Dried Out Slider Diaphragms and Intake Manifolds
What Do the Reviews Say?
The CL powerplant was very similar to the CB’s. The parallel twin’s 180-degree crankshaft had four bearings, a ball on the left end and three rollers, with needle bearings on the connecting rods. Keep them all lubricated and that crank could happily go 100,000 miles. The cylinder barrels were alloy, using cast iron liners and alloy heads, with two valves per cylinder. None of this pushrod nonsense, as a single overhead camshaft powered by a chain running between the two cylinders did all the work.https://ridermagazine.com/2018/01/10/1965-1968-honda-cl77-scrambler-305-retro-review/
What Is the Resale Value of the Honda Scrambler?