Pros and cons of 2 stroke and 4 stroke engines

Pros and Cons of 2 and 4 Stroke Engines

2 Stroke Engines

Pros
Cons
Simple to produce
High noise levels
Easy and cheap to manufacture
High Pollution levels (caused by burning of oil with the fuel)
Relatively high power output for CC
Low fuel economy
Ideal for smaller motorcycles and scooters up to 125cc due to low production cost and good power output
Narrow power band
Due to the way oil is burnt in the cylinder, re-bores are required every so often

4 Stroke Engines

Pros
Cons
More even power spread across the rev range
More complicated to produce than a 2 stroke engine
Good fuel economy
High manufacturing costs due to more complex design
Lower levels of exhaust emissions
More efficient engine system

Please note: As a general rule, due to lower manufacturing costs and simplicity of design, 2 stroke engines have been commonly used in motorcycles and scooters up to 125cc, motorbikes and scooters over 125cc have tended to be mainly 4 stroke.
But, as technology has advanced, most of the problems associated with either 2 or 4 stroke engines have been or are being engineered out.
So, although smaller engines still tend to be 2 stroke and larger motorcycle engines tend to be 4 stroke, engines have remained this way due to manufacturing costs rather then because of limits in design or engineering technology.

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