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Home › Forums › Shifter Karts › Violent Jerking in Beginning of Power Band
Tagged: 125 shifter kart
I am new to shifter karts, and just drove my 125 shifter for the first time this past weekend. One thing I noticed was that when I started to get on the gas midway through a corner, just getting into the power band, the kart would violently jerk forward and back, so much that I either had to let off the gas, shift up, or get on the gas harder. Is this normal?
I’m new to shifters too and still sore from my first outing. :P
The power and acceleration compered to anything else is brutal but jerking is never a good thing and it’s not normal.
I would say to check your pilot and needle as they control the low to mid range. good luck
The only time I ever experienced what you are describing (as long as there wasn’t an issue with the motor) would be when I downshifted too far (should’ve stayed in 3rd rather than go to 2nd) and I would be too high in the RPM range and any little throttle input would feel like a jerk until I shifted up (or I was too high in the RPM and hit the rev limiter).
What were the RPM’s like when you felt this? If you don’t think it is your driving may I suggest asking someone at the track who drives a shifter to take some laps in your kart to make sure it is running right.
Something that might give you an indicator if the motor is running okay is while on the stand (after warming it up to operating temp) pull the throttle to get around 7000-8000 RPMs, hold for a brief moment, and then yank the throttle and see if there is any hesitation getting to max RPMs (should max somewhere in the 14000 range). All this is meant to tell you is without a load, can the motor rev up without issue given the current setup/conditions. If there is hesitation at any point (after the inital delay from yanking on the throttle) than it’s time to start looking into the potential problems.
To follow this up under load is while on the track (pick 3rd or 4th gear), get the RPMs about 7000 and punch the throttle. The motor should bog and about 8500 it should launch to about 12500 before it loses power. Repeat this (same gear at the same point on the track) but start at 8500 and it should immediately launch to around 12500 before the power drops off.
This is assuming you are running a Honda stock moto…
As Juan mentioned, these things are brutal!!! (but ohhhhhh so much fun) :)
Sounds to me that you may be too lean on your needle…fatten it up a bit…’specially if its a honda.. just my 2 cents !!
Before you do anything to the motor, try adding a second throttle pedal return spring. It’s common for new shifter drivers to bounce the pedal and adding a spring will help.
Everybody’s advice might be right.
First time in a shifter will make it very difficult to diagnose, if you ‘re still in over your head a bit.
At this point, I’d definitely let someone with a few laps in a shifter try it and give you some feedback. It could just be the way you’re driving it. Or it could be an actual problem with the kart / engine.
One thing that important when learning to drive a shifter, if you touch the gas pedal the rear plants down, if your not through the turn enough it will be very hard to drive. Driving a shifter fast is all about patience and timing. In my experience with an ICC the ” violent” jerking is usually too rich on the bottom. The engine has lots of power and when you feed it fuel it wants to go, later as you get better, and “time it” better you will want all that power. Howie is right on with the second return spring, also make sure that your leg isn’t pivoting outwards as it usually will hit the throttle as well. When you get it right there is nothing better than driving a well balanced shifter. Best of luck.
Thanks for the suggestions everyone. I’ll try to do all of these things next time I take it to the track.
Jetting is off
Sounds Rich in the low to mid range (throttle position)
try leaning the needle (honda)/ emulsion tube (if ICC)