Surging is pretty bad on the single spark engines (pre 2005)

you can somewhat fix them with the following fixes:

Use 87 gasoline only and not higher

Get a different sparkplug:
If you are still having some surging issues with your fuel injected F650, try this: change the regular spark plug to an NGK #DPR8EA9 spark plug (found at any H*nda Dealership). The only difference between this spark plug and the DR8EB (currently in the bike as per BMW specs) is that this is a "projected tip" spark plug. What it does is move the explosion deeper in the combustion chamber (2 or 3 millimeters). I've been riding with this DPR8EA9 spark plug for over 400kms, and its like riding a brand new bike, one that has just about no "surging" or "bucking" when riding at a steady throttle. This fix as also improves mid throttle acceleration. It is a "racing" inspired fix originally meant to improve performance. So, it will not hurt your motorcycle and at worst will only improve performance. It's dirt cheap, more or less $3us


Denso projected tipped plug X24EPR-U9)

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