There’s a special kind of thrill in finding a classic machine like the 1987 Polaris Trail Boss 4×4 sitting in a barn or listed for a bargain. You see past the faded plastic and cracked seat, envisioning the trails it once conquered and the adventures that still lie ahead. It represents a pivotal moment in off-road history—one of the very first 4×4 ATVs that set the stage for everything that followed.
But bringing a vintage quad back to its former glory can feel daunting. You might be wondering where to even start, what common issues to look for, or how to keep it running reliably. You’re in the right place.
We promise this comprehensive guide will give you the confidence and know-how to tackle common issues, perform essential maintenance, and get that two-stroke beast roaring back to life. We’ll cover its unique history, walk through a pre-ride inspection checklist, dive deep into the most common problems and their fixes, and share some best practices for keeping it running strong for years to come.
What Makes the 1987 Polaris Trail Boss 4×4 an Off-Road Icon?
Before we grab the wrenches, it’s worth understanding why this machine is so special. The 1987 model wasn’t just another ATV; it was a game-changer. It brought true, on-demand four-wheel drive to the masses, forever changing what riders could expect from a utility quad.
The benefits of 1987 polaris trail boss 4×4 ownership today are rooted in its simplicity and historical significance. Unlike modern, computer-controlled machines, this quad is almost entirely mechanical, making it a fantastic learning platform for the aspiring DIY mechanic.
Key Features That Defined a Generation
- The 2-Stroke Powerplant: The 250cc two-stroke engine is simple, lightweight, and delivers a snappy powerband that’s just plain fun. It has a distinct sound and smell that screams vintage off-road.
- Polaris Variable Transmission (PVT): This was Polaris’s pioneering automatic CVT system. It eliminated the need for manual shifting, making the ATV incredibly easy to operate on tricky terrain. Just gas and go.
- On-Demand 4×4: With the flip of a switch, the rider could engage the front wheels. This early system used electromagnetic clutches in the front hubs, a technology that was revolutionary for its time.
Owning one is like owning a piece of off-road history. It’s a testament to a time when machines were built for function, and their raw, unfiltered performance created a connection between rider and trail that’s hard to find today.
Your Essential Pre-Ride Inspection: A 1987 Polaris Trail Boss 4×4 Care Guide
Before you even think about firing up that engine, a thorough inspection is non-negotiable. This is one of the most crucial 1987 polaris trail boss 4×4 best practices. A few minutes of checks can save you from a long walk back to the truck or a costly repair.
Follow this checklist every single time you ride.
- Fluids, Fluids, Fluids: Check the two-stroke oil level in the reservoir under the seat. Ensure the transmission fluid is at the correct level via the dipstick. Lastly, check the brake fluid reservoir on the left handlebar—the fluid should be clear, not dark and murky.
- Tires & Wheels: Check tire pressure (typically 3-5 PSI). Look for cracks in the sidewalls or objects embedded in the tread. Grab each tire at the top and bottom and try to wiggle it; excessive play could mean a bad wheel bearing.
- Brakes & Controls: Squeeze the single brake lever. It should feel firm, not spongy. Make sure the throttle lever snaps back cleanly when released. Check that the choke cable moves smoothly.
- Chain & Sprockets: Inspect the drive chain for rust, stiff links, and proper tension (about 1 inch of slack). Look at the sprocket teeth—if they look hooked or sharp like a shark’s fin, they’re worn out and need replacing.
- Lights & Electrical: Turn the key on and test the headlight (high and low beam) and taillight. Most importantly, test the engine kill switch to ensure it works instantly.
- Fuel Check: Open the gas cap and take a sniff. If the fuel smells like old varnish, it’s bad and needs to be drained. Old fuel is the number one enemy of a two-stroke engine’s carburetor.
Tackling Common Problems with the 1987 Polaris Trail Boss 4×4
Every old machine has its quirks. This 1987 polaris trail boss 4×4 guide wouldn’t be complete without addressing the issues you’re most likely to encounter. The good news is that most of them are straightforward fixes for a DIYer with basic tools.
Engine Won’t Start or Bogs Down
This is the most frequent complaint. Remember the three pillars of a running engine: fuel, spark, and air.
- Fuel System: The carburetor is almost always the culprit. Ethanol in modern fuel can gum up the tiny jets inside. The fix is to remove the carburetor, disassemble it carefully, and clean every passage with carb cleaner and compressed air. A carburetor rebuild kit is cheap and a great way to replace old gaskets and seals.
- Ignition System: Start with the easiest fix: a new spark plug (an NGK BPR7ES is a common choice). If that doesn’t work, check the spark plug wire for cracks. A weak or non-existent spark could also point to a failing CDI box, though this is less common.
- Air Supply: Pull out the air filter. If it’s caked in dirt and oil, it’s choking the engine. Clean it thoroughly with filter cleaner or replace it.
4×4 System Not Engaging
You flip the 4×4 switch and… nothing. This is a classic issue with the early magnetic hub system.
The most common cause is a break in the wiring that runs down the A-arms to each front hub. These wires are exposed and can easily get snagged or corroded. Inspect them closely. You can use a multimeter to check for 12 volts at the connector near the hub when the switch is engaged. No voltage means the problem is likely the switch or a break in the wire further up.
Clutch and Transmission (PVT) Issues
If you hear grinding noises, feel the quad shudder on takeoff, or notice it just doesn’t have the “get up and go” it used to, your PVT system needs attention.
Remove the clutch cover and inspect the drive belt. It should be free of cracks, glazing, or frayed edges. If the belt looks good, the clutches themselves are likely dirty. Dust and grime can prevent the clutch sheaves from moving smoothly. Clean them with compressed air and a Scotch-Brite pad—never use lubricants or solvents on clutch faces.
How to Perform Essential Maintenance on Your 1987 Polaris Trail Boss 4×4
Proactive maintenance is the key to reliability. Learning how to 1987 polaris trail boss 4×4 maintenance tasks yourself will save you money and build your confidence. Here are the core jobs you should master.
The 2-Stroke Engine: Oil and Fuel
The oil injection system on these machines can become unreliable with age. Many owners choose to disable it and switch to pre-mixing fuel and oil in the gas can. This ensures the engine always gets lubrication. A ratio of 40:1 (3.2 ounces of oil per gallon of gas) with a quality two-stroke oil is a safe bet.
Transmission Fluid Change
This is an easy but critical job. Warm up the quad for a few minutes, then locate the drain and fill plugs on the transmission case. Use a ratchet and socket to remove the plugs, let the old fluid drain completely into a drain pan, and refill with the correct amount of Polaris AGL or a compatible gearcase lubricant. Don’t overfill!
Carburetor Cleaning
Learning to clean your carb is the most valuable skill you can have for this ATV. As mentioned earlier, it involves removing it from the engine, taking off the float bowl, and using carb cleaner to spray out the main jet, pilot jet, and all small passages. It’s a meticulous job, but it’s the solution to 90% of running issues.
Sustainable and Eco-Friendly Tips for Your Vintage ATV
Keeping a classic machine on the trail is a great form of recycling, but we can do more. Adopting a few sustainable 1987 polaris trail boss 4×4 habits protects the trails we love for future generations.
An eco-friendly 1987 polaris trail boss 4×4 approach starts with responsible maintenance and operation.
- Proper Fluid Disposal: Never dump used oil or other fluids on the ground. Collect them in sealed containers and take them to your local auto parts store or municipal recycling center. Most accept used oil for free.
- Use Modern Oils: Modern semi-synthetic or synthetic two-stroke oils burn much cleaner than the conventional oils of the 1980s. They produce less smoke and fewer harmful emissions.
- Stay on the Trail: The single best thing you can do for the environment is to stay on designated, established trails. This prevents erosion and protects sensitive habitats.
- Keep it Tuned: A clean air filter and a properly tuned carburetor mean a more efficient engine. It will use less fuel and produce fewer emissions, making your ride a little greener.
Frequently Asked Questions About the 1987 Polaris Trail Boss 4×4
What kind of oil does a 1987 Polaris Trail Boss take?
The engine requires a quality 2-stroke injector oil if the stock system is used, or a 2-stroke pre-mix oil if converted. The transmission/gearcase uses a specific fluid like Polaris AGL (All Gear Lubricant) or a compatible 75W-90 gear oil.
How fast is a 1987 Polaris Trail Boss 4×4?
In good running condition, you can expect a top speed of around 40-45 mph. Speed will vary based on engine health, clutch condition, tire size, and rider weight.
Are parts still available for this model?
Yes, surprisingly so! Common wear items like drive belts, brake pads, carburetor rebuild kits, bearings, and seals are readily available from aftermarket suppliers. Major components like engine cases or plastics are harder to find and often require searching used markets like eBay.
What is a common problem with the 4×4 system?
The most common failure point is the wiring that runs to the front hubs. These wires are exposed to sticks, rocks, and moisture, leading to breaks or corrosion. Always check the wires first if your 4×4 stops working.
The 1987 Polaris Trail Boss 4×4 is more than just an old ATV; it’s a rugged, simple, and historically significant machine that offers a pure, unfiltered off-road experience. It demands a hands-on approach, rewarding you with the satisfaction of keeping a legend alive.
By following this guide, performing regular checks, and not being afraid to get your hands dirty, you can ensure your vintage Trail Boss is ready for any adventure you throw at it. Now get those tools out, give that old quad the love it deserves, and hit the trails. Ride safe and have a blast!
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