Reply To: GD250N – Hanging Revs and Stalling when Throttle opened quickly
Hello again!
Finally decided to take off all of the fairings and troubleshoot again, after the bike recently started to idle at about 4000rpm and rev hang got worse. (Can’t comfortably ride, if you need to slip the clutch on upshifts to get the revs down)
Went to measure the resistances for the coils and for the cap itself
Cap/Cable -> 10.3 kOhm
Primary -> 0.6 Ohm
Secondary -> 6.7 kOhm
I should get around to checking the injector, but I currently have no idea on how to clean it and it’s a bit challenging to get to.
– IAC Experiments
I’ve been playing around with the IAC some more because it seems most plausible to me.
I checked one more time to see if it’s a vacuum leak, which it doesn’t seem to be. The airbox pulls hard when you cover the opening, the idle normalizes, rev hang is improved and if you cover it more, it stalls.
I did some adjustments to the throttle follower setting (how quickly the IAC closes when you close throttle) as well as its parking position, which works pretty well until it somehow goes back to lagging and idling high
which I think is due to it becoming miscalibrated (adressed further below)
see video (this was directly after a flash re-calibrating the IAC position and settings):
https://www.youtube.com/shorts/0WL2oA8j36M (didn’t mean to upload it as a short, mb)
– IAC Calibration
I decided to remove the IAC to inspect it, it looked fine, I cleaned off minor grime.
After some messing around and measuring, I discovered, that the valve would not fit into the throttle body, when first calibrated to the pintle seat and then moved out all the way. It was off by about 24 steps.
I assume that, basically when telling the IAC to fully close (position 0) it’s physically stopped from moving at position 24 while thinking its position to be 0, so it would be miscalibrated by +24 (more open).
For some reason the IAC also seems to get quite hot when the bike is on (50°) not sure if this is normal considering it’s a stepper motor
I’m still unsure at the moment, I haven’t found a tune that gets the behaviour I want to stay for longer than a few minutes. (did get one very nice ride where revs dropped nice and fast for quick shifting, which lasted about 5 minutes)
and I’d still be puzzled as to why it started doing this in the first place. I’ll see if I can find a replacement IAC, in case this one is broken or damaged.
Could a dirty fuel injector cause this behaviour? it seems to be running lean, but I don’t understand how it would be idling at 4k
Thanks for any ideas and tips!