The Mini Moto is a small scale replica of World Super Bikes used by likes of Valentino Rossi and ex champion Carl Fogarty. The Mini Moto comes equipped with either a two stroke air or water cooled engine which are, depending on model, capable of speeds of up to 60Mph.
In this article I will underline finer points of components that make these speeds possible.
The two Stroke Engine
The two stroke engine produces more hp per pound than four stroke engine. The two stroke engine consists of three moving parts, piston, rod and crank. The piston acts as valve that opens and closes intake and exhaust ports that are located on walls of cylinder. Unlike four stroke engine that fires only every other time of pistons movement, two stoke engine fires every time piston reaches top of its travel. This means that time spent generating power is doubled in two stroke engine than that of four stroke engine, as there is no engine coasting during passive cycles. This is main reason that two stroke engine can rev more highly and produce more power (for its size) that four stroke.
The two stroke engine needs to be run on a mixture of petrol and two stroke oil. This is so that engine is kept lubricated whilst in use.
99% of all starting problems are caused by fuel problems. These can stem from bad or old fuel and improperly mixed fuel (please see mixing chart). Do not use fuels that contain alcohol, as can cause you bike to run ‘lean’. Be advised some racing fuels contain alcohol and are best avoided.. We recommend that you use normal petrol for a garage and a quality two stroke oil.
A mixture that is too lean I.e not enough two stroke oil can damage your mini moto’s engine as moving parts are not properly lubricated. This can cause engine to seize. However a mixture that is too rich can choke engine and effect performance and cause starting problems. You can tell if your mini moto is running too richly by plumes of white smoke coming out of exhaust and lack of performance. A rich mixture (25:1) is needed to lubricate engine during ‘run in’ period, you may experience a lack of performance during this period. The pocket bike may run more slowly and acceleration can be sluggish, however when you change to a mixture of 50:1 you will really notice a difference. The leaner mix ignites in combustion chamber faster and with a more explosive force than richer mix. This means higher revs which means more power and acceleration. We recommend that a fuel mixture of 25:1 is used to ‘run in’ you mini moto, and a mixture of 50:1 is used thereafter.
Your mini moto should be ‘run in’ for first 3-4 tanks of fuel. During this period we recommend that you use a fuel mixture of 25:1. This means a mixture that is made up of 25 parts petrol to 1 part of two stroke oil. During ‘running in’ period be careful to not rev engine to its maximum as this can damage engine. The ‘running in’ period will allow moving parts to become well oiled and clutch and brakes to ‘bed’ themselves in. After you have run minimoto on this fuel mixture for 3-4 tanks, check chain and tighten accordingly, check tyre pressure, tighten bolts on brakes, forks and wheels. You may also need to readjust throttle settings to allow for higher revs that changing to a leaner fuel mix produces. The bike should now be ready for a fuel mixture of 50:1.
The mini moto uses a centrifugal clutch to power drive sprocket, which in turn drives back wheel of your mini moto. When you start your mini moto clutch spins as engine ticks over . The clutch is engaged when you pull back on throttle. The increase in speed of revolution of clutch makes clutch expand and grip inside of clutch bell which turns sprocket that drives back wheel of your pocket bike. The clutch can be set up in different ways depending on type of performance that you want from your minimoto. Adjustable clutches are not standard on mini moto’s but an after market Polani or Blata style adjustable clutch can be used in your new mini moto. These allow rider to adjust mini moto’s set up in according to their preference. Setting clutch to engage too late when engine has built up too much power may cause clutch to slip and never fully engage. This can result in excessive wearing. However setting clutch to engage too early, before power has built up in engine can cause your pocket bike to ‘bog down’, resulting in slow acceleration. The perfect set up is to get clutch to engage just as engine has built enough power to rocket mini moto away, but without making clutch slip, this is achievable through trial and error.
Making sure that your spark plug is fresh is important in a two stroke mini moto engine. You can tell a lot from colour of spark plug. The top part of your spark plug is covered in ceramic insulator which, when brand new is white. This part of spark plug can change colour according to how your engine is running. The plug should appear as a nice tan colour when engine is running perfectly, this indicates complete combustion. A greyish or white colour indicates that engine is running too lean which can result in engine damage. In this case you should clean and check your fuel system for any obstruction, check your fuel mixture, check for loose intake manifold bolts and carburettor mounting leeks, faulty gaskets and leaking crank seals. Anywhere that your engine could potentially leek and suck in fresh air can be source of a lean condition. A blackened or oily spark plug indicates improper combustion and is result of running too rich. This can be caused by too much oil in mixture or spark plug could be faulty and misfiring. Check fuel mixture and replace spark plug.