Air filter (for Minarelli Horizontal engines)

The Minarelli Horizontal is one of the most popular scooter engines (used in the Yamaha Aerox, MBK Nitro, Aprilia SR, Malaguti F12 and others). As these engines are often modified, choosing the air filter is a critical step towards getting the engine to run properly.

The main types of air filter for the Minarelli engine

1. Original style (airbox):

   • Intended for: Standard engines or mild "Sport" tuning.

   • Advantages: Gives the best protection against dust and dirt, runs quietly, and the engine is less sensitive to changes in the weather.

   • Tip: If your airbox is intact, the best option is to fit a quality performance sponge inside it (e.g. Malossi Red Sponge). This gives better flow without changing the design of the original box.

2. Performance (open / pod filters):

   • Intended for: More powerful projects (70cc and above).

   • Advantages: Maximum airflow, aggressive sound.

   • Tip: These filters "eat" far more dirt. If you ride on dusty roads or in rainy weather, they are not the right choice, because the engine will wear faster and a soaked filter can "choke" the engine.

Technical notes and important details

• Carburettor tuning (essential!): If you replace the original airbox with an open performance filter, you must re-jet the carburettor. Much more air will enter the engine, so the mixture will go "lean". This causes the engine to overheat and the piston to seize.

  • What to do: You will need to fit a larger main jet (main jet) – usually 10–20% larger.

• Oiling: Any sponge (whether in the original box or a performance filter) must be oiled with dedicated air filter oil. Without it, the filter simply lets fine dust straight through into the cylinder.

• Mounting diameter: Before buying a performance filter, measure the diameter of the carburettor intake (usually 28 mm, 35 mm or 42 mm). Minarelli engines with the original Dell'Orto carburettor usually use a 35 mm connection.

FAQ: frequently asked questions

Does the Minarelli Horizontal airbox fit all versions? Yes, the Minarelli Horizontal airbox mounting points are identical, but there are two types: the "old" type (with a simple tube) and the "new" type (usually with a longer, more shaped intake tube). They are interchangeable, but the carburettor sometimes needs a little adjustment.

What if the scooter cuts out in the rain? If you are using an open performance filter, this is a normal consequence – water gets into the filter and upsets the mixture ratio. The only solution is to go back to the original airbox or make a splash guard that protects the filter from direct dirt and water thrown up by the rear wheel.

When should the air filter sponge be replaced? If the sponge has started to crumble, has gone "soggy" or cannot be washed clean – replace it. Minarelli engine cylinders are sensitive to abrasive wear (dust).

The air filter is the "lungs" on which the service life of your Minarelli engine depends.