Information (help) sought.

[oldrider]

New kids bike problem.

Kawasaki KX65, six speed two stroke. (Pictured below)

Problem is, instability at speed, virtual tank slapper.

Problem is the same despite size and experience of rider.

Makes things a bit difficult for young riders to maintain stability in a straight line, especially with power on.

We have checked the bike over for any apparent defects and have made all the easy adjustments for no real change to the behaviour of the bike.

Any suggestions or experience from you guys out there would be appreciated.

This thing has got plenty of snot and goes really well otherwise. Cheers John.

[kro]

What sort of surface are you mainly riding on?, I have ridden a few small bikes like this that will behave really badly on some surfaces, but well on others. The bike is obviously quite new, so I take it head and wheel bearings will be ok?.

Is there drag on the front brake at all, does it spin freely?. Oh, and agressive front tyres can behave a bit strangely too sometimes, as I discovered quite by accident.

[Danger]

It sounds like you are describing head shake? Not swapping. Has the suspension had any work done to it? Make sure the rebound damping is not too heavy or the high speed compression damping is not too heavy (has some one put heavy oil in these forks)? How heavy is your rider and what year is the KX?

If you have tried different clicker settings and the forks have not been worked on ensure proper sag setup for your rider. Then check these points.

Chassis not straight.
Chain adjuster of creating misalignment of wheels.
Too high a tire pressure.
Tire not mounted properly on rim. Wheel out of balance.
Loose steering bearings.
Forks pumped up with air. Be sure to bleed before riding with front wheel of the ground.

Check the forks are not bound up by following these steps.

1.) Install both forks and set fork height using calipers or a ruler. It is important that fork height be exactly the same for both sides.

2.) Install the axle and tighten the axle nut to proper spec. If the axle turns while tightening, tighten one right side axle pinch bolt to hold axle in place.

3.) Tighten both left side axle pinch bolts to spec.

4.) With the bike on a stand and wheel of the ground and left side axle pinch bolts and axle nut tightened, loosen the right side axle pinch bolts. Take a small flathead screwdriver and carefully tap it into the slot between the two right side axle pinch bolts. This will enlarge the axle hole. You will then be able to grab the bottom of the right side fork tube and push it in and pull it out freely. The fork will settle naturally into position on the axle without binding.

5.) Remove the screwdriver and tighten the right side axle pinch bolts to spec.

If you're wondering if your forks are currently bound up, put your bike on a stand and start this procedure at Step 4.

Good luck and it can be hard to analyze the problems for a young rider as often they are not very good at describing what the bike is doing, but start with the above for head shake symptoms.

[oldrider]

Thank you Danger and kro for your replies.
The bike is brand new, straight from the dealers.
I will pass the information that you have supplied to my son in law and he can take it from there.
I will let you know any outcomes as I appreciate your help. Cheers John.

[oldrider]

Well we have checked, checked and rechecked the bike and could find nothing out of order.
Aaron finally changed the handle bars, cutting 40mm off each side, then refitting and lowering the setting down as far as possible.
Bingo, the bike behaves beautifully with any size aged rider.
For a little bike this thing has really got some snot and I have to be proud of my wee grandson for the way he handled it while it was thrashing around all over the place.
Tonight he was out there giving it rings and it never missed a beat in the handling department.
The brush busters were not able to be put on until the bars were finally set up, they are putting them on tonight and giving another work out tomorrow night after the boy gets home from school.
I had a ride on the bike myself but it just showed me how old I am getting but for such a small bike 65cc it sure does get up and go.
You would not credit how much influence the handle bar width and placing could have on the handling of this bike!
If the refitting of the brush busters has any undue effect I will post, otherwise, thanks for the help you guys who responded to the call for help. That's what KB is for! Thanks again, John.

[TLDV8]

The brush busters were not able to be put on until the bars were finally set up, they are putting them on tonight and giving another work out tomorrow night after the boy gets home from school.

I hope they are not the alloy Barkbuster type that clamp to the bar on the inner and then plug into the outer end of the bar.They can be wrist busters if you go over the bars.

[Danger]

Thanks for the update. Moving the bars forward if the bike has the option will increase stability/slow down the quickness of the steering and provide the pilot more control over the handlebars. Glad you got it sorted.

[oldrider]

Believe it or not putting the bark busters back on started the bloody weaving motion going again maybe not as bad but still very noticeable!
Took them off again and motion "gone" so they are staying off now.
If I hadn't seen it I would not have believed it, you learn something every day!

Just have to get the little guy mastering smooth gear changing both ways and he will be more able to make better use of his bikes very precise power band and concentrate on mastering the bike's total capability. Looks like he's going to have some fun with this thing! Cheers John.

[soundbeltfarm]

If you put the bark busters back on have them a bit loose where they mount into the end of bar.
so if you come off over the front and get your wrist stuck in them they will pivot and hopefully help stop your wrist from breaking.

i was told this when i was younger.
and ive seen people come off and break wrists .
not a good look.

[Danger]

Not a good look! And good advice. Guess I've been lucky as far as wrists go, despite breaking two hands in the last year. Don't think I'll tempt fate any longer and I'm going to loosen my bark busters before my next ride. I've heard of people doing this, but never seen it. In fact I've only been over the bars three times in my life that I can remember and the bike has always come over and landed on me so everthing has remained relative. But still, why temp fate?
Oldrider now you are describing the problem as weaving? That sounds different to head shake that I thought you were describing and in your first post you talk about a virtual tank slapper? I'm still not sure about the nature of your problem.
Run those barkbusters loose, but run them. I smashed my right hand ring finger into a sawn of branch end (spookilly enough the branch came up under my barkbuster and struck like a hammer blow) into six places (like broken cornflakes the Doctors described it) last year and have limited use of my hand now. Can only really grip with two fingers and it plays havoc with my bike control as I tend not to use the front brake much cause it means I'm not gripping the bike with my hand while braking. The branch got under the bark buster this time but that was just the angle of the branch that was sticking up at a 45 degree and my suspension was dropping into it. Just a fluke and most times the barkbuster would have deflected the blow.