Benelli Bella 25 / S50

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INDEX

Specifications

Property Specification
Engine type 2 stroke (1:50 mix) membrane intake
Engine content 49cc
Bore size 40mm
Factory carb jet size 50
Fuel tank capacity 3L
System voltage Either 6V 17W or 12V (17W?)
Ignition system Either mechanical or CDI
Rated speed Bella 25: 25kph / S50: 45kph

Ignition timing

Property Specification
Points opening distance 0.4mm
Spark plug gap 0.6mm
Ignition advance on flywheel (17 degrees?)

Gearbox

The Benelli 50cc gearbox takes 600cc's of oil.
Originally it would have taken 30w20, but this type is hard to find. SAE 30 monograde has proven to work well from experience and is widely available online.

Performing oil changes isn't difficult as you only have to loosen a 6mm inbus bolt at the bottom right of the gearbox cover.
The bolt is ealily identified as all other bolts are slightly smaller (5mm inbus). Removing the bolt entirely of course speeds up the draining process.

If you are removing the cover entirely, mind that the gasket can be quite stuck to the engine and cover and is easily torn. Finding or making a new gasket is a rather dificult proces.

Cylinder and piston

The Benelli 50cc engine has a 40mm piston. The cylinder is made of cast iron.
After some investigating I found that Minarelli 40mm pistons and 40mmx1.2mm rings fit without issues.

Engine exploded view


Click the image for full size

Documents and media

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