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 solutionCam chain guide inspection
Inspect the cam chain guide in the following procedures:
remove the cam chain guides. Refer to “cam chain guide / cam chain
tensioner removal and installation” .
Check the contacting surface of the cam chain
guides. If it is worn or damaged, replace it with a new
one.
...
Starter torque limiter removal and
installation
Removal
Remove the clutch assembly. Refer to “clutch removal” in section 5c .
Remove the washer (1), starter idle gear no. 1 (2)
And starter torque limiter (3).
Installation
Installation is in the reverse order of removal. Pay
attention to the following point:
apply ...
Clutch lifter pin inspection and adjustment
Refer to “clutch removal” and “clutch installation” .
Note
when inspection and adjusting the clutch
lifter pin, it is not necessary to install the
clutch onto the countershaft.
Inspect and adjust the clutch lifter pin in the following
procedures:
assemble the ...