Does this look weird?

[johnatthebox]

Im having steering wobble issues and I was wondering if any mini bike tech gurus out there would look at these photos and tell me if anything super-obvious jumps out at them. The front end turns ok. The wheel bearings are all good. Tires arent flat. It does kinda ride high. It goes ok up until about 20 mph and then (under acceleration) the front end will start to
to shake until I let off the throttle, and then it will stop.

 

[Havasu Dave]

You may not have enough trail. (Google "rake and trail" if you haven't heard the term) Since you already have the front end configured, a taller front wheel/tire diameter is the only solution IF that is the problem.

I had the same problem on a mini bike. I found that by moving my weight back a bit, I was able to control it. You may need to move your weight forward under acceleration. It's a neat bike, by the way.

 

[SimpleTom]

Try a different wheel and tire on the front and see if it still does it.

 

[Spyderdregg]

Maybe its how the picture looks but is the front wheel higher then the rear wheel or does the bike sit level?Don't know if that would make a difference but figured I'd ask.

 

[bigrob]

As Tom suggested a different rim and tire , but first put it up on blocks to spin the front wheel to look for wobble (rear too)

 

[Havasu Dave]

LOL, SMH.

Look at a close up of the front tire sports fans.

 

[SimpleTom]

LOL, SMH.

Look at a close up of the front tire sports fans.

:shrug: Guess I don't see it?

 

[SimpleTom]

Directional tires? Arrow on the sidewall? The rear looks like it would be on backwards.

 

[JKautoFab]

rear is on backwards but wont cause that much trouble. he said front tire but i dont see anything wrong with it in any of the pics

 

[SimpleTom]

rear is on backwards but wont cause that much trouble. he said front tire but i dont see anything wrong with it in any of the pics

Right, I know he said the front tire. But since the rear is on backwards I thought that is what he was refering to.

 

[johnatthebox]

Maybe its how the picture looks but is the front wheel higher then the rear wheel or does the bike sit level?Don't know if that would make a difference but figured I'd ask.

when its on the ground it sits pretty darn level, BUT when I am added to the picture, it sits a little like a drag car(down in front). Theres still some travel in the legs. Its not bottoming out or anything....

 

[johnatthebox]

As Tom suggested a different rim and tire , but first put it up on blocks to spin the front wheel to look for wobble (rear too)

new bearings- spinning true

 

[johnatthebox]

LOL, SMH.

Look at a close up of the front tire sports fans.

I know, I know, the rear IS on backwards, because the pocket bike i cut it off of had a right-side chain, and I havent gotten to switching it around to the other direction. Im surprised no sports fans mentioned the rear brake setup mounted upside down as well. You guys gettin lazy or what?

 

[johnatthebox]

It rolls ok, its when i give it throttle after about 15-18 mph or so, it shakes . I lift, and it calms down , when i twist it again, its back ....

 

[bikebudy]

Try the other wheel an tire to see if it stops, like other have said.

My guess is that the tire vs. the wheel is not mounted true. ( Causing a low speed wobble.)

 

[johnatthebox]

Try the other wheel an tire to see if it stops, like other have said.

My guess is that the tire vs. the wheel is not mounted true. ( Causing a low speed wobble.)

stupid question Im sure, but do you mean one of my wheels is not mounted straight on my frame, or one of my tires is unba[anced on the rim?

 

[Havasu Dave]

stupid question Im sure, but do you mean one of my wheels is not mounted straight on my frame, or one of my tires is unba[anced on the rim?

I wouldn't consider 20 MPH on six inch wheels is a low speed wobble. But I was referring to the mud in what little is left of the treads causing an imbalance, along with the fact that there is no tread/traction on the road. When you installed the front end, where you didn't establish rake angle so you could get trail. Does it have trail? Can you flip the lower legs 180 degrees, then remount? If so, that would quickly answer that question as you got the axle more aft.

I tried to edit your photo with lines and words, but maybe you can see enough to see what I mean about trail. Think of a shopping cart, and how it needs to run with the mass pulling the front end. Two wheeled machines need this same concept. Mass pulling from in front of the axle, not pushing from behind it.

 

[SimpleTom]

stupid question Im sure, but do you mean one of my wheels is not mounted straight on my frame, or one of my tires is unba[anced on the rim?

No, Maybe one of your wheels is bent causing the wobble. Swap it out with a different wheel/tire and take it for a ride.

 

[SimpleTom]

It rolls ok, its when i give it throttle after about 15-18 mph or so, it shakes . I lift, and it calms down , when i twist it again, its back ....

It could also be engine shake common with the Predator engines. :shrug:

 

[Havasu Dave]

It could also be engine shake common with the Predator engines. :shrug:

....setting up a harmonic vibration through the frame, shaking the front end, and with no tread, and mud keeping it out of balance, and with zero trail, causes it to vibrate. :laugh: Plenty of these ran with original 400 series front ends with no shake. Maybe get rid of the oleo struts, and use a bit of 1971 coil spring. :thumbsup: