Throttle roll-on surge.

[RC390 Fan]

My RC has the Akra pipe and map but still has that annoying surge when I roll the throttle on at the apex of a corner. It really upsets the bike.

I dont know if remapping can fix it (maybe by adding fuel at the lower rpms?) but I was thinking about simply increasing the engine idle speed in the meantime. Because it seems like this engine doesnt like to come off idle very smoothly.

Any thoughts on this?

 

[guzz46]

I'm not aware of any such surge.

 

[SPG]

I increased the idle to reduce engine braking on corner entry and allow a smoother roll on. Seems to work fine. I haven't yet researched if there is some part of the ECU which is trying to force the RPMS lower like on some EFI systems and was at the track, so I made a relatively small change. Probably 2000-2200 rpm. My Ninjette idle was set at 3000....
-Sean

 

[RC390 Fan]

I increased the idle to reduce engine braking on corner entry and allow a smoother roll on. Seems to work fine. I haven't yet researched if there is some part of the ECU which is trying to force the RPMS lower like on some EFI systems and was at the track, so I made a relatively small change. Probably 2000-2200 rpm. My Ninjette idle was set at 3000....
-Sean

Ok then I think I will increase idle speed and try it out.

guzz46- It happens when going from compression/trail braking into a turn (throttle off) and then adding throttle to exit. It makes the bike jerk a little bit, which is not good when you are close to the edge of traction.

 

[Ryanthegreat1]

Do you know the rev range this is happening at? Maybe try running a gear lower? More revs to get out of closed loop.

 

[ArkansasDave]

Only surge I've felt is at 7500 rpms or so and figured it was just hitting the power band.

 

[RC390 Fan]

Do you know the rev range this is happening at? Maybe try running a gear lower? More revs to get out of closed loop.

Its just the transition between throttle off (comp braking) and throttle on, which usually happens at the apex of a turn. And the higher the revs (lower geasr) the worse it is. Sure you can corner in a higher gear but then the bike will lug out of the corner.

 

[guzz46]

I've never experienced any surge when getting on the throttle after corner entry on my RC, in fact its pretty smooth, I'm not sure what's going on there?

 

[SPG]

Ok then I think I will increase idle speed and try it out.
.

BTW, I just checked and adjusting the throttle plate is not teh ideal way to accomplish this. There is a throttle speed actuator in the wiring diagram, so the EFI is trying to hold the idle speed.
-Sean

 

[Willasan]

Try some maintenance throttle through the corner before you roll on?

 

[Ryanthegreat1]

Could it be slop in the drivetrain? Loose chain or too much play in the cush drive?

I did not notice any mid corner hesitation at a track day or on the street.

 

[Treachery]

I've never experienced any surge when getting on the throttle after corner entry on my RC, in fact its pretty smooth, I'm not sure what's going on there?

My experience matches this. Are you running the akra map?

 

[RC390 Fan]

BTW, I just checked and adjusting the throttle plate is not teh ideal way to accomplish this. There is a throttle speed actuator in the wiring diagram, so the EFI is trying to hold the idle speed.
-Sean

Thats what I was afraid of.

 

[RC390 Fan]

My experience matches this. Are you running the akra map?

Yes I have the Akra pipe and map.

I can pull the clutch in and feather it as I roll on but it is hard to do it perfectly every time with this bike.

I did raise the idle speed (adjusted the throttle stop) but it seems like the ecu is trying to fight the higher idle. Not sure about that.


Edit: And just to be clear I should mention that I am not new to bikes. I have decades of riding experience and years road racing under my belt, I just find that when I'm on the edge with this bike I have trouble with the throttle response. I usually raise the idle on all of my race bikes but this one doesnt seem to like that, and I'm just trying to find a better solution.

Maybe I need a slipper clutch, IDK.

 

[RC390 Fan]

Found the problem. It was ME!

It turns out that the throttle-stop adjuster on the throttle-body is not a good way to adjusted engine idle. You see when I first got the bike I turned the screw in to try and raise the idle because it had stalled on me a few times. At first this seemed to do the trick (I thought) but then the idle was a bit erratic; it would almost stall, surge and just not idle consistently.Especially when it was warming up. Once warm it would idle higher. Done, right? Wrong! So now when I'm coming into a corner, throttle off, clutch out (compression/trail braking), the idle would sometimes surge and make the bike jump, totally upsetting the geometry at THE worst time.

Today I backed the screw out to its factory setting (or close) and the surge went away. So... nevermind.

 

[KwicK To Master KTM]

You are not alone on this one. I have done exactly what you did by adjusting the idle speed to loose the rough idle - And up until know have just thought it was the bikes personality to surge in the throttle off roll on .
Although I do not track ride I found this happening when least expecting it in round abouts - Which has caused some nasty moments.

I will now adjust my idle speed back to stock as you have done. That's the best thing about forums like this - the glitches get solved!!! Thanks for the post

 

[Treachery]

All's well that ends well...