Possible explanation for abrupt throttle

Lately I've noticed that my 6th gen has exhibited a sharper-than-usual throttle response. It seems intermittent though, but tonight it was doing it a lot. I paid real close attention and I think I have an explanation.

I think the throttle position sensor (TPS) has a dead spot near closed-throttle. Most fuel injection systems have a "deceleration mode" wherein the injectors are cut off when the throttle is closed (as indicated by the TPS) and the engine speed is above a certain threshold (1500-2000 RPM on cars, for example). The goal is reduce emissions and improve fuel economy whilst coasting.

When my bike is acting up, it is clear that the engine remains in this "deceleration mode" until the throttle is twisted a little bit more than usual. This makes the bike feel like it's jolting forward because the injectors are turned back on when the throttle is opened a little more than where it should be.

Note that the throttle response while at idle seems pretty consistent and crisp, but that is because the engine is sitting below that threshold RPM.

Imagine a stereo with a volume control labeled 0 through 10 as well as a Mute button. While coasting, the volume is on "0" and the Mute function is on. When the volume (or throttle in this case) is turned to "1", the Mute function is turned off. This should give a subtle transition from silence to low volume.

Now when my bike is acting up, it is as though the volume has to be turned to "2" or "3" before the Mute function is turned off. This gives a much less subtle transition.

I'm not sure if the TPS is adjustable or replaceable, but I plan to take a look at it to see.

Any thoughts?

 

Only that if you figure out how to fix it let me know! I adjusted my throttal cable so there is almost zero play and that helped a little. But I have to say that this thing is a light switch, its on or off. And that dam surging under light excell, bummer. But hey maybe an air filter and some cans will help "decongest" this thing. :unsure:

 

i experience the same on/off throttle response. it's extremely annoying. i had a Ninja 650R as my previous bike and it was very smooth. i keep telling myself that i just need to improve my own technique and it will happen with time, but i'm beginning to think I'm not the problem. let me know if that filter helps things Stuka.

 

You can adjust the TPS -BUT- its a pain in the a55. I"ll try and dig up where I found out how, it was on one of the english VFR sights. I thought I had messed mine up when I had it off the bike (actually had not got the connector all the way back in). You have to uncover the caps on the adjustment screws and then use a volt meter to adjust to the correct settings. The service manual says its nonadjustable and you should replace the entire throttle body as a unit if you have a bad TPS. I would be very sure that I had a TPS problem before I started messing with it. Good luck and I hope you get it figured out.

Action

 

I thought the same thing and I know its not me anymore. It's not so bad when I'm on the the bike because I know it's going to happen and I'm ready for it. I have to keep reminding my GF to hold on when we are moving slow in traffic or parking lots anywhere we are moving slow.