HSP Atomic Warhead 4WD nitro buggy

This is probably the cheapest 4WD nitro buggy available.

My nephews bought this one on ebay for A$280.

You also need to buy a starter kit with glow plug battery, fuel bottle and tools for about $30, and fuel for about $17 for a litre bottle. We bought our fuel from Tates Toy Kindom www.tates.com.au in Geelong.

I put this page together to address the regular requests for help that come via my YouTube page.

We no longer have this buggy so all this advice is from memory.

PLASTIC PARTS

This is a cheap entry level buggy made with plastic gear cogs and suspension parts which do wear out but are easily replaced. I guess more expensive buggies would be more rugged and durable, but for the money the Warhead is a lot of fun and a great starter.

Spare HSP parts are available from www.myrc.com.au

OUT OF THE BOX, OUT OF CONTROL

When my nephews first unpacked the buggy they fuelled it up, connected the glow plug battery and pulled the starter cord. Chaos erupted.

The buggy fired up, revving at full throttle, totally out of control. It scared the wits out of everyone, stripped one of the gear cogs and probably reduced the lifespan of the engine to some extent. It eventually stopped when someone pulled out the fuel tube.

The boys would not go near it for ages and we had to work out how to replace the stripped gear and gain control of the wild beast.



SET UP CHECKS

Our buggy was not set up correctly in the box.

On the handset the throttle switch was in the wrong position meaning that pulling the trigger reduced the revs rather than increasing revs. It needed to be switched to REVERSE to work in the correct way. Not that this would have made any difference because the carby was sitting in the fully open position and the throttle linkage stops were loose. No amount of trigger pulling would have changed the out of control revs at startup because the linkage could slide freely not operating the carby.

So the first big tip is to check that the controls actually work the way they are supposed to and that all screws and bolts are tightened.

When you pull the trigger the carby should open and when you let it go it should return to the starting position with the brakes just coming on. When you turn the steering knob clockwise the wheels should steer to the right.

On the handset there is a foward/reverse switch and a fine adjustment knob for throttle and steering.

RC receiver units do not like being switched on without a signal to receive. So always turn on the handset first so that a signal is available for the receiver. Also turn the handset off after the receiver so that the signal is always available when the receiver is trying to receive.

Handset on first THEN receiver on. Receiver off first THEN handset off.



CORRECT RUNNING IN

To make these nitro engines run well and keep on working you need to run it in. I’m no expert on his but do a search for “Nitro tuning” on Google or YouTube and you will find heaps of good onfo.

The chaps at Tates told us to use lower percentage fuel to start off, that’s the yellow 5% car and buggy fuel, and don’t rev flat out for the first 1 litre of fuel. Run it rich also for that first 1 litre which means the engine should produce smoke when it’s running, and may sound a bit rough. This keeps the engine running cooler and well lubricated during the running in period.

Then change to the blue 10% car and blue buggy fuel for full performance. To be honest it was plenty fast enough for us using the “slower” yellow fuel.

With our buggy, possibly due to it’s out of control beginning, engine tuning was always difficult. It often cut out due to overheating even though it was running rich and smoky.

FUEL MIX

One of the main adjustments to the buggy performance is the fuel mixture screw. This regulates the mixture of fuel and air going into the carby. A rich mix has higher ratio fuel and a lean mix has less fuel. Screwing anti-clockwise makes the mix richer and clockwise makes it leaner.

Running the engine in requires a rich mix producing blue smoke. To start off the screw will be just poking out above the barrel as in this photo.

Once the engine is run in you need to gradually turn the screw clockwise ¼ turn at a time to make the fuel mix leaner. When the tuning is correct it will only produce smoke at high revs and should run smoother and faster. If you make the mixture too lean the engine will overheat and stop. Try to avoid this, it's not good for the engine.

STRIPPED GEAR

Our first task was to remove the gearbox and replace the stripped gear.
The buggy is very easy to take apart and work on. Make sure you don't lose any screws or nuts and remember which bit goes where. It is quite modular comprising engine and clutch as one unit, gearbox and brakes another unit. The cogs on the clutch housing mesh into the gear cogs and the wheels are driven via 6 drive shafts sitting in slotted cups. Everything is screwed down to the aluminium base. The suspension and fuel tank are and held rigid by the top plate.

Here are some videos covering dismantling and the gearbox.

Dismantling the buggy

Replacing the gear



BROKEN CLUTCH SPRING

The next problem we had was the buggy always wanting to move even when idling. This may be the clutch shoes grabbing when they should be held in by the clutch spring.

Remove the motor by undoing the 4 mounting screws underneath. Then remove the clutch housing by undoing the central screw. The spring that holds the clutch shoes in tighly will probably be broken or unhooked. Mine had just broken the hook off one end so I was able to bend out one turn and hook it back into a loop. Then you slip it back into the groove around the shoes, this takes a bit of force.



Here's a video showing Dismantling the clutch



It's a good idea to make up a mobile garage or carry box like this to keep everything together and make dismantling easier.