HPI Baja 5B: The Classic 1/5 Gas Buggy, Specs and Ownership Guide
The HPI Baja 5B is a 1/5 scale two-wheel-drive gasoline buggy that helped define the large-scale RC class. It’s about 817 mm long, with a 570 mm wheelbase and a dry weight of about 9.6 kg. Standard kits and RTRs use a 23 cc two-stroke Fuelie engine running on petrol mixed with two-stroke oil, and the limited SS kit uses a 26 cc Fuelie 26S. The truck version, the Baja 5T, shares much of the chassis. Huge aftermarket support makes the 5B one of the most modified RC cars ever made.
By Kyle HilsonUpdated: October 20263 min read
Specifications
| Item | Value |
|---|---|
| Scale / drive | 1/5, 2WD (rear) |
| Length | 817 mm |
| Width (F/R) | 460 / 480 mm |
| Height | 255 mm |
| Wheelbase | 570 mm |
| Weight | About 9.6 kg (no fuel) |
| Engine | 23 cc Fuelie; SS: 26 cc Fuelie 26S |
From HPI’s published specifications.
5B or 5T?
The 5B is a buggy with open wheels, lower and lighter, and handles tracks and smoother ground well. The 5T is a short-course style truck with a full body and bumpers that protect it in crashes and rough ground. Many parts are shared. If you want to know whether to buy a 5T RTR, the choice comes down to style and terrain; see HPI Baja 5T.
Speed
A stock Baja 5B is commonly reported around 35–45 mph, depending on engine, gearing and tyres. Bigger engines, pipes and gearing push it faster. See fastest 1/5 scale gas RC cars.
Maintenance
- Clean and oil the air filter after every run in dust.
- Check the spark plug and kill switch.
- Inspect clutch shoes and springs.
- Check brake pads and the brake linkage.
- Re-tighten engine mount and suspension bolts.
- Use the right fuel/oil ratio.
Engine tuning
Baja engines use Walbro-type carburettors with high and low needles. Tune slightly rich for engine life. Carburettor tuning is covered in Walbro 1107 carburettor.
Common upgrades
- Larger engine or big-bore kit.
- Tuned pipe.
- Stronger steering servo and servo saver.
- Aluminium or stiffer suspension parts.
- Better air filtration.
- Different tyres for terrain.
Buying today
New availability varies by region and version. Used 5Bs are common; check the engine compression, clutch, gears and frame for damage. Compatible chassis from other makers share many parts. Large cars are compared in 1/5 scale RC cars.
Safety
At nearly 10 kg, a Baja can cause injury. Run it only in open spaces, test the failsafe and kill switch, and carry the car with the engine off.
History
HPI introduced the Baja 5B in the mid-2000s, bringing a large, ready-to-run gas buggy to a mass market at a time when most RC cars were 1/10 electrics or 1/8 nitro. Its rear-engine layout, huge tyres and simple, tough design made it popular for bashing, and an enormous aftermarket grew around it. Several versions followed, including the 5B SS kit, the 5T truck and the 5SC short-course truck, as well as Flux electric variants. Many other makers later built compatible or similar chassis, which is why so many large-scale parts fit the Baja.
First run tips
Break in a new engine gently with a few tanks of moderate driving, keep the mixture rich at first, and let it cool between tanks. Check all screws after the first session, since new cars often loosen as parts settle.
FAQ
What engine does the Baja 5B use?
A 23 cc Fuelie; the SS kit uses a 26 cc Fuelie 26S.
How heavy is it?
About 9.6 kg without fuel.
How fast is it?
Commonly around 35–45 mph stock.
Should I buy a 5T instead?
Choose the 5T for a protected truck body, the 5B for a lighter buggy.
More on this topic: the complete RC Cars guide covers the basics behind this article.
About 20 years in RC. Mostly boats in the NAVIGA Mini Eco Expert class, with many self-made parts; also a King Motor Baja 5B, a home-built electric plane, home-built nitro planes he has flown, and an RC helicopter. More about SwellRC
