Hobao Radio Controlled Nitro-Methane Powered Truck

I now own a Hobao 1:8 scale radio controlled monster truck. It's powered by a nitro-fuel 2 stroke engine and can get up to 30mph+. I've made lots of mistakes, broken a few things and learned some stuff. I'm hoping that if I document them here either it'll help others not make the same mistakes, or perhaps recover from them easier. Also, maybe I won't repeat them (though this is, of course, not guaranteed).

Photo of the Ofna Hyper .21 8port nitro-fuel engine

The Engine

The engine is an Ofna "Hyper 21 8 port". It's a 3.5cc 2 stroke, with 2.5 horse power output and a max rpm of 38k.

It's ABC type piston liner which this stands for Aluminium piston, Brass cylinder liner and Chrome coating on the surface of the brass liner. It has no piston ring and instead and relies on a very tight piston/cylinder fit. This makes it very important that it's broken in properly.

It has an SG crank, also known as a pilot shaft (P-shaft) or european shaft. "the pilot shaft is built into the end of the crankshaft, while standard engines have threaded crankshafts and require a clutch nut with a built-in pilot shaft" - Crankshafts perform dual duty in 2-strokes engines. They transfer the combustion power to the drive train and also regulate the air/fuel mixture that is delivered to the crankcase. As the engine rotates, the port opens and closes beneath the carburetor.

The Fuel

The fuel is a mix of methanol and nitro-methane.

Carburetor

The carb controls the flow of fuel and air into the engine. Slide carbs commonly found in .21 engines provide more bottom power and quicker response. Most .12 engines have a rotary carb which is less responsive, but easier to adjust.

Breaking in a new engine

Starting

Hold finger over the exhaust pipe during first few pulls to force fuel through.