Othen

There are lots of possible causes.
Sometimes it is a good idea to trace one’s steps since the fault first occurred. Did it start suddenly? Is it intermittent or permanent? Is it getting worse? Try to think back and be methodical (make a list of all the things that have changed and try to correlate causes and effects).
When you try to diagnose the fault only change one thing at a time, and make a note of what you do and whether it affects the bike. Try the cheapest and simplest things first (plugs, impedance of the caps and coils, continuity of the wires and connections and so on).
It might be a good idea to post any results you get as you check the bike here, the chances are someone will have had a similar experience and so will be able to save you lots of time.
Good fortune,
Alan


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