Check the engine oil level as follows:

The engine oil level should be between "L" (Low) and "f" (full) lines.
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Caution The engine oil level must be between the " l'' (low) line and "f" (full) ~i ne, or engine damage may occur. Check the oil level, through the inspection window, with the motorcycle held vertically on level ground before each use of the motorcycle. |
Engine oil
Engine oil and filter changeSpecial tools and equipment
Recommended service material
Note
required service material is also described in the following.
“Front brake master cylinder components” “rear brake master
cylinder components” “rear brake pedal construction”
Special tool
...
Use of sds diagnosis reset procedures
Note
the malfunction code is memorized in the
ecm also when the lead wire coupler of any
sensor is disconnected. Therefore, when a
lead wire coupler has been disconnected at
the time of diagnosis, erase the stored
malfunction history code using sds.
After repairing ...
DTC “c28” (p1655): secondary throttle
valve actuator (stva) malfunction
Detected condition and possible cause
Detected condition
Possible cause
The operation voltage does not reach the stva.
Ecm does not receive communication signal from the
stva. Stva can not operate properly or its motor locked
Stva malfunction.
...