Originally Posted by
WR6133
Easiest to start with is fuel
Clear the breathers on the fuel cap (unlikely but it takes 5 minutes to do and remove from equation).
Drain the fuel filter in to a clear glass, you are looking for water. If there is any hint of it drain the tank.
If the above don't work then it's time to check the fuelling pipes, pump flow, etc. Was the air filter changed? If it was a line may have been pinched in the process or the airbox may not have been resat correctly.
I'd be shocked if the fuel is "stale". I've got a Novemeber/January mix in the ZZR and it's fine. Heck when I bought the thing it had a full tank of 9 month old and was fine. I wouldn't have thought IACV would have an effect at 4K RPM, I'm not that hot on EFI but I believe it should only effect idle.
If none of the above work then I'd be trying
TPS - When the TPS went on my GSXR I had a similar symptom but it was up at 8k RPM. Scour around the net you'll find a guide on checking and setting the TPS for your model bike. It's an easy but slightly fiddly job.
Coils - Does the tach needle bounce about a bit when it happens? Could be ignition coil related, though I'd check this last as it's a pain in the arse to properly test coils and also I don't think it's very likely as if a coil was dying you'd expect the problem to get progressivley worse under load.
That one is a myth (my old man worked in the industry). Refineries don't store boatloads of spare fuel to go stale. The only difference between supermarket and garage is the detergents (including ethanol) added to the petrol, same base product from same refineries (Anything in this area will have come from the refinery in Fawley). Contamination usually comes from the forecourt tanks and there is a thought (which maybe a myth) that supermarkets wait longer intervals before cleaning the tanks.
