KZ throttling bounces

Hi,

I’ve seen some onboards on the track i race of other KZ and i see their acceleration is sooo smooth between gears, on the other hand mine isn’t that way, i can start accelerating and the engine starts bouncing as if there were many potholes on the asphalt, I moved from the circuit where I train recently to go to a new one, in the old circuit i didn’t have this issue, I’ve only drived three days on this new circuit, I have a GoPro and i can clearly see my problem on the videos comparing it with other drivers onboards, it’s like we are driving on a different asphalt, i’m a bit mad about this hope somoene can give me a hand.

Thanks

I had a similar issue when I first started driving at NTK after having only driven at DKC. After reviewing my video footage, I found my leg/foot were bouncing off the throttle cable. I purchased a bicycle de-railer cable stop and moved the throttle cable sleeve end point closer to the pedal and problem went away.

I don’t know if it was because the track was tighter/twistier or had differences in grip that was causing my foot to bounce around so much. Before, OTK has the sleeve terminate just in front of the seat at the waist of the kart. Now I have it terminate just in front of the “C” for the hubs.

Hi Greg, here i will leave a video where you can see the hopping, its not an extreme hopping but its not smooth while accelerating: https://youtu.be/TOLpOQBjcmE
I dont know if its the same hopping you had

Its hard to determine if the issue you have is the throttle jumping and that’s it, or if your chassis is hopping which in turn is causing the throttle to jump as you are being bounced around. If you chassis is hopping there is another thread on that topic that can help that. If it is just the throttle being bounced around you might try stronger or more springs somewhere either on the carb or on the pedal. You might have to work on both.

Hi, thx for your answer,

Here you have my footage:

Here you have other guy footage on the same track without the problem i have:

You can clearly see that his throttling is more smooth than mine, like i’m driving in another track, i have to battle so much the kart on the exit because power delivery is not smooth, and that didn’t happend to me on the other track and you can see it here:

He’s driving better (though clearly not perfectly and I don’t have lap time comparison) and looks stronger physically. You’re hyper aggressive and erratic with your inputs as well inducing quite a lot of understeer and then not able to control the kart when it grips and brings the rear around. I don’t know your physical condition but I’d recommend some decent calisthenics training as well. Heel supports might help too.

This is what you need to watch and study -

That’s my take anyway.

It was also my first day on that track, i know i have to improve also, i’m agressive but as you can see on my video of the other track i’m not that erratic, but is the feeling i have on the new track that the kart is much more undriveable than in the other track and it’s clear on the videos, i cannot take that smooth progressing throttle, i know i have to improve my driving but i think something is wrong on the kart also

You’re driving the same on the other track

Yes in that day i had a bit more oversteer


But not on this one for example, but i’m not here complaining about the oversteer, there are many factors about having that or not, track condition, tires, etc…but you can clearly see on these videos that the engine delivers the power smoothly while it doesn’t on the other track, i know my driving on the other track has something to do about it but i still think something is not working like in the last video track

you shouldn’t be moving that far forward in the seat under braking.

So, I’d first of all look at seating position. I can’t really tell but you look a bit bolt up right to me. This might contribute to issues if you can’t hold yourself properly. Driving a KZ with the wrong seating position is horrible. Add in erratic inputs and it might be a recipe for disaster at some tracks.

Now that I have seen the video, I am in agreement with @Alan_Dove. Your steering inputs are very fast initially and then a lot of correction. I have not driven KZ only TaG. As I understand it, KZ has loads of Torque out of the corners thanks to a 6 speed gearbox and with front brakes, its more of a pointy cornering thing than arcing with single gear drive. In both videos for several corners it looked like the rear was stepping out under acceleration. I know grip levels can affect that, but you also have to Drive the Track. Have you tried rolling onto the throttle rather than just flat to the floor? Listening to the engine rev along with the video, it seemed like the rear was fighting for grip on corner exit, which would explain why the throttle feels so twitchy.

I might suggest slowing down your hand movement and rolling onto the throttle on corner exit to start and see if that makes an improvement in engine response. Could also be a gear ratio thing. If its too torquey out of the corners, go down a tooth on the driven sprocket and see it that helps. In either case, you have to slow down your hands. You are asking the kart to do too much too quickly.

As I understand it, moving the seat back in KZ compared to TaG, has to do with improving the rear grip with the higher Torque. The more weight you have over the rear tires will reduce the how much the tires break traction on hard acceleration.

Just some things to consider…

Thank you for your answers and advices,
I truly want to go smooth and have an smooth acceleration, i know i can improve and change my driving style but i feel like if i dont go that agressive on that track the engine will fall of rpm, seeing other drivers onboards it seems they have more margin to drive smooth than i have because their engine keeps high all the time, its difficult to explain here, i also see my mistakes on the onboard and i will go mentally different the next day i go to the track but still have the feeling of not having margin on low-mid range rpm, i truly want that progressive acceleration because driving like that its not even fun and very unsatisfying, some people told me i can also make some jetting adjustments, i will try with changing my way of driving but i think i can work with jetting too

Its odd but I can see what you are saying. Its like you are having difficulty being progressive with the throttle in the bottom half of the throw. The power comes on like you are hopping and then causes your kart to get all unstable.

The other footage wasn’t as bad.

It could be that you are just rusty and you are overdoing it putting down the power, causing the kart to start hopping, which makes it worse.

Yes its exactly that, i’m struggling to find the sweet spot while accelerating to get that progressing power delivery, i feel an extreme hopping that i didn’t feel in the other track, i will try different way to accelerate the next day and also be more smooth with the wheel but i still have the feeling that jetting or something it’s not correct, specially because the hopping has increased so much just because changing the track

Hello

I had the same exact issue on my CRG 175 road rebel. I bought the kart winter 2020 and had my first drives this spring. All was good - no issues - had quite a few track days - everything working just fine

But one day arrived to the track and kart was doing just what your kart is doing. I couldnt first understand what was happening. Kart was very sensitive to throttle input.

Then remembered I had changed throttle cable the previous night as old cable had cut slot to tillotson bracket and wasnt very smooth. So figured cable must be causing the issue as it doesnt have friction anymore. Loosened throttle cable a bit at the track - that helped somewhat and by squeezing the gas tank with my legs I could drive through the day. I could see my angle/shoe touches the cable if any side movement happens

I fixed the issue by moving cable to side of the pedal. Never have had the same issue happen again

Mikko

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Hi Mikko,

It’s strange because my father also have the same issue as me, he has also a crg 175 and the issue increased a lot by changing the track as you can see on the videos, it really feels like the throttle pedal is not going well, feels like the pedal is spiking, we didn’t changed the throttle cable when we changed the track.

I’ve been thinking these days that is a jetting config problem because I think we are going too rich. I will try what you are saying the next day, will squeeze my legs on the fuel tank and loose a bit the throttle cable and see if still happens and if it works I will move the throttle cable as you did to not touch it with my foot. I’m sharing a photo of how i have the throttle cable putted. Hope I fix this soon and thanks.

A few things I would check/do:

  • Are the pedals close enough? Having to reach too much will not allow for as much control.
  • Install a heel stop if you haven’t already.
  • Install additional springs on the throttle pedal to stiffen the movement, and prevent against the pedal being able to bounce if you’re driving on a bumpy track. I run 1-2 springs depending on their strength.
  • Drive less at partial throttle.
  • Experiment with jetting: needle type, clip position, pilot jet, etc. All of these will affect initial throttle application before full throttle.

EDIT- disregard my previous thought of moving the throttle cable to the top loop. I had a brain fart and somehow confused the relationship. Moving to a lower position will lengthen the throw, so you look like you’re already in the lower position.

Hello Bob and fellow members

Heres my set up. I moved the cable to the side - to lowest position possible. As the engine is somewhat angry in its manner - having slower ratio gives finer control ability to butterfly. I quite like how it is - would have moved the cable even further down if there was place for it. Moving cable down causes it to rub more on front stabilizer mount

Loosening the cable on track was just quick fix to get me through the day. On the same day my friend tried my kart and was done in two laps - he was terrified of the jerky throttle and was scared running it. I noticed he is shorter than me so didnt reach properly to heel supports. He also had quite fat shoes with ankle protectors that touched the cable

My thinking is to try to have zero slack in cable. Specially if having any plastic hose/protection around the cable loop - It makes the loop quite a bit stiffer. Bigger the loop is - more pedal travel is needed to make tension. By pressing the pedal cable doesnt get any tension until loop has shrunk in size and become more rigid - then cable actually starts moving the butterfly. I could see it by watching the whole assembly and moving pedal with my hand.

If - for example - doing repairs on track and having to remount the cable - with big cable loop you now most likely have quite different ratio on pedal than in previous session. For me that kind of change doesnt make my laptimes any better :smile:

Running without plastic cover is great but I dont like how cable eats trough pedal eyelets etc

So I have zip tied the cable/hose assembly to as small loop as possible.

As Evan already suggested - in my setup the spring is on top eyelet. It made throttle stiffer = better for fine control. Maybe second additional spring would make it even better

I like to keep every control system on my kart tight ie steering, brakes, pedals etc. Any slop just delays my inputs

Anyway - After this cable mod I havent had to grip gastank with my feet

Mikko

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Thank you all for your dedication to help.
I will try tomorrow all the things, specially with Jetting and throttle cable/pedal setup, I will let you know how it turned out.

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Hi everyone,

I finnally fixed it with jetting and pedal setup, now i have more pedal travel as also a leaner jetting.
Really thx

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