Are the jet settings stock? Are you using the airbox? Make sure the filter is clean.
Check the settings against the table in the Technical Resources section. (Make sure use identify the correct carburettor for your bike - MC21 will either be TA22A or TA22B.)
It's very important to synchronise the carbs and to get the air screw settings correct for a smooth idle. You should also have a good, well charged battery, and start the motor with the lights turned off to reduce the drain on it.
Make sure the oil pump is set correctly as per the instructions on the Tech pages.
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Andy.
NSR-WORLD.COM
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Please DO NOT PM me for technical advice. My time is precious, and you will probably receive a faster response on the Forum anyway.
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