South West Bikers | Motorcycle Forum

So the superduke has been a naughty little f##ker lately, under about 4k it was stuttering like a good un, felt like fuel starvation but pretty sure it wasn't.
the bike was only rideable if you kept it about 5k ALL THE TIME, drop the revs for a corner or traffic and it would buck and twitch like a junkie going through withdrawal.

checked the plugs
cleaned the air filter
checked the various electrical connections
changed the fuel filters
disconnected quickshifter to make sure it wasn't iinterferring
adjusted throttle
found the throttle tube was coming undone from cam so fixed that

then i had run out of ideas.

Next was to call in the tech expert (jug inspector) and get his big brain working.

Took the bike up to him and the testing began, he'd already done a ton of research, got the TunECU sorted to see what the Austrian zx81 level ecu was sharing, figures made some sence but not definitive with an answer. Out came the multimeter and component testing began.
Eventully it was tracked down to a TPS (throttle position sensor), instead of a noce linear resistance as the unit was opened up, it was all over the place)
A new one was ordered, which took an age (still waiting for 2 seals ordered on June 5th) and thenthe fitting and setup could begin. Installation is not too tricky although setting it up to .6v would of sucked had it not been for TunECU as you can see the result straight away from any adjustments.
Installed, rebuilt and up and running i took it for a spin, no stuttering! Such a relief.

Still had to do a TPS setup (15 mins tickover to allow it to settle itsself) and then another test ride. This showed that the idle speed was too high(throttle stop had been raised by a local dealership trying to smooth out the low rev problems but didn't realise it was the TPS), that's been backed off now so the next test ride awaits......

Big thanks to Jug for his big brain, tech help, time and coffee making skills.

Glad we got it sorted and I learned more about the 990 along the way, so I'm ready for if/when mine does it.

So after the RTTB cruise control system that would not allow the engine to go below 3000 revs (which for a twin is 1/4 of the rev range)

Have you managed to dial out the high tick over?

Could be that the throttle cables were just too tight so not letting the ECU adjust it back far enough when properly up to temperature.
Billi likes no slack in his cables, mine has a few mill of slack at the twist grip so that could be why his started to rev hang once it was fully up to temp.

I don't know why it didn't do it on the first test ride though, which was straight after fitting & setting up the new TPS.