Oil quality is a major contributor to your engine's performance and life. Always select good quality engine oil. Suzuki recommends the use of suzuki performance 4 motor oil or equivalent engine oil. Use sf/sg or sh/ sj with jaso ma in api (american petroleum institute) classification.

Api: american petroleum institute jaso: japanese automobile standards organization
Sae engine 011 viscosity
Suzuki recommends the use of sae 1 ow-40 engine oil. If sae 10w-40 engine oil is not available, select an alternative according to the following chart.

Jaso T903
The jaso t903 standard is an index to select engine oils for 4- stroke motorcycle and atv engines. Motorcycle and atv engines lubricate clutch and transmission gears with engine oil. Jaso t903 specifies performance requ irements for motorcycle and atv clutches and transmission.
There are two classes, ma and mb. The oil container has following classification for confirming the standard.

Energy conserving
Suzuki does not recommend the use of "energy conserving" oi ls. Some engine oils which is api sh or greater has "energy conserving" indication in api classification doughnut mark.
These oils can affect engine life and clutch performance.
Fuel
Engine coolant solutionEngine top side assembly
Assemble the engine top side in the reverse order of
disassembly. Pay attention to the following points:
Cylinder head
Install the dowel pins and a new cylinder head gasket
(1) to the cylinder.
Caution
use a new gasket to prevent gas leakage.
Place the cylinder head ...
Pair reed valve removal and installation
Removal
Lift and support the fuel tank with the prop stay.
Refer to “fuel tank removal and installation” in section 1g .
Remove the air cleaner box. Refer to “air cleaner box removal and
installation” in section 1d .
Remove the pair control solenoid valve (1) along with the ...
Oil jet removal and installation
Piston cooling oil jet
Removal
Remove the engine assembly. Refer to “engine assembly removal” in
section 1d .
Remove the crankshaft assembly. Refer to “engine
bottom side disassembly” in section 1d (page 1d-
49).
Remove the piston cooling oil jets (1) from the upper
cra ...