Gen 1 standard fuelling

[GrahamB]

I had similar symptoms with an old FZ750 I rebuilt. Tick over fine, spluttering under load until high revs reached where it seemed fine again. Cause was corrosion in the HT leads where they screw into pug caps. Connection wasn't bad enough to cause problems unless the engine was under load.
Where plug access is a problem it always makes me wonder how many "mechanics" decide that replacing them is too much trouble & just don't bother. Solution? Change them yourself.  8)