Reply To: Miss and backfire under 5k only after engine warms up – 2009 GT650R
The coils are retrograding , if sparks came out (arc’ing) , replace either SV99 or GT650 pre-2010 coils (same coil maker) and replace the caps as a good measure. Readings may be OK but may be arc’ing when running. SV99 caps should fit OK or another set of OEM hyosung caps for now. However “magnecor” HT wires are recommended over the stock black HT wires.
Pulse sensors are not normally changed on their own , and can be a messy process if not sure how to do it without cutting and chopping wires up , there should be loads of posts online about 650’s burning the stator plugs when the connectors have rust in them (resistance goes up!) Clean the connectors as best as you can and try to avoid the rear tyre thrown stones or water at them.
Go on ebay and type in “SUZUKI HARNESS BOOT” , this MUST be used to hide plugs under the airbox and near the rear shock. I do this on all my hyos and customer ones (rains a lot in UK!)
Hyosung used one boot for the headlight (55 watts down those plugs!) , so you will have seen it.