| ial engines. They are still used by several | | | | What’s the difference between the |
| manufacturers (most notably Blata on their entry | | | | series I’ and series II’ |
| level bike) and typically produce between 2.5 and | | | | crankcase?. Fuel is drawn from the carb into the |
| 3.5 horse power (hp). All are air-cooled. Tuning and | | | | crankcase via a one-way valve known as the |
| performance parts are very limited. | | | | reed valve’. The intake port (where the |
| The Chinese 47/49cc. These engines are used in | | | | reed valve and carb join the engine) on the series |
| the Chinese made mk2, and mk3 minimotos. | | | | I engine will only accommodate a reed valve |
| They are air cooled and produce between 2.5 and | | | | assembly with one reed petal’ whereas |
| 3.5 horse power (hp). This engine is different from | | | | the series II will take a reed valve |
| the industrial engine that is used in the Blata, as it | | | | cage’ that accommodates two reed |
| is specifically created for mini moto use. | | | | petals. A two-petal reed valve will allow more fuel |
| Polini 4.2 engine. This is the basic Polini engine and, | | | | mixture to flow into the engine and, therefore, |
| as its name suggests, it produces 4.2 hp in | | | | produces more power. |
| standard form. It is air-cooled and uses the | | | | Polini Super engine. The super also uses the series |
| series I’ crankcase with the 3-port | | | | two crankcase but with a 5-port cylinder. It is only |
| cylinder. There is plenty of scope and parts for | | | | available in water cooled now but used to come |
| tuning but few people bother because most racing | | | | as air cooled as well. To compete with Polini, |
| classes for the 4.2 won’t allow any | | | | Mallossi manufacture an alternative 5-port cylinder. |
| modifications. | | | | There are no restrictions on tuning supers and |
| Polini 6.2 engine. The top end of this engine is the | | | | with engine porting’, bigger carbs and |
| same as the 4.2 (3-port) but is available with | | | | other performance parts they can be turned into |
| either water or air-cooling. The bottom end uses | | | | awesome machines (for their size) easily |
| the series II’ crankcase. This helps to | | | | producing 12hp. |
| make it more powerful. Race regulations | | | | What is meant by 3 and 5 port?. This refers to |
| don’t allow modification to the engine | | | | the amount of transfer’ ports built into |
| internals but do allow performance parts, the | | | | the cylinder. The transfer ports draw the fuel |
| most significant being the exhaust. There are a | | | | mixture up from the crankcase and |
| wide range of alternative exhausts that year | | | | dump’ it above the piston prior to |
| after year manage to extract more power from | | | | ignition. A five-port cylinder has potential to |
| the engine. Consequently the 6.2 tag’ | | | | produce more power. |
| no longer means anything, these little rockets | | | | 40cc or 50cc. The 3 port engines are only |
| (more often referred to as production’ | | | | available in 40cc. The 5 port cylinder comes in |
| nowadays) claim power outputs of up to 9hp. | | | | both 40 and 50cc. ZPF offer a tuned 5-port polini |
| The Chinese made water cooled engine. This | | | | cylinder with their own special’ cylinder |
| engine is very similar to the Polini 6.2 however it is | | | | head. The extra cc gives 25% more displacement |
| a series 1 crankcase engine. The engine is water | | | | and, therefore, has the potential for more power. |
| cooled and is used in the Origami B1 replica. The | | | | 50’s are more common in the USA but |
| engine produces around 7.5/8.5 horse power (hp) | | | | they're catching on fast in the UK. The UK now |
| Many of the parts on this engine are | | | | allows them to race in championships. |
| interchangeable with the Polini. | | | | |