Front end wobble or bounce... ?

[MrSavvy]

Alright. Crashed my bike a year and a half ago, roughly. Always tight on money, fixing it has been slow. Not a lot wrng with the bike, but I digress.

Recently completed work is as follows:
1. Replaced front wheel bearings and seals (All Balls).
2. Replaced both upper fork tubes, oil, dust caps, seals, etc.
3. Replaced upper triple (needed new ignition, key lost). Triple wasn't damaged in crash.
4. Bought brand new Bridgestone tires (Battleax, something 45's [forgot exact name, at a movie]).

After all of this, I just took the bike to Street and Trail to have them mount and balance the tires, double check the front alignment (on the fork/wheel/triple).

The bike handles superb. The turning is easy as butter, there's no veering if I let go of the handle, and there is barely any wobble if I let go of the handles while riding or slowing down.

The problem I have is this constant, very rapid bouncing on the front-end. The mirrors bounce up and down by a milimeter or so, my arms vibrate a bit, etc...
It doesn't get better or worse with speed changes (as far as I can tell), or with baking.

Also, after replacing the steering bearing, there's a metallic clunk on the front-end when going over a small bump of any sort.


I will say; I saw, on one of the welds on the frame under the gas tank, there is a small crack in the paint. Made more evident by a small amount of rust.

This is my first motorcycle, my first 250. So I have nothing to compare this bike to.
But my mechanical instincts are usually prettty accurate.

Any ideas what could cause the metal clunk? Or the bouncing shuddering deal?

Thanks guys

Edit 1: first observation after getting the bike back from Street and Trail; they didn't put a new cotterpin on the front wheel axle? It went in with a pin installed...

[subxero]

can't say, perhaps you could do some things to help trouble shoot.

Metal clunk over bump? something with your internals of the fork tubes? did you just put everything back normal did you change your preload spacers?

As far as the shudder Try getting up to speed and pulling in the clutch, this takes a lot of engine vibe out of the equation and also quiets things down so you can hear more of what is going on. You said it doesn't get worse or better with speed? Does the frequency change at all? If the frequency of the shudder changes they obviously it has to be related to a moving part that changes speed like the wheel. Is it balanced correctly? did you lose a weight?

Is there any play in anything that has bearings when the bike is on stand?

[csmith12]

Sounds like you need to tighten up the head nut some more.

Do this;
Get a friend
Have the friend help you hold up the bike
You stand over the front wheel
Push sharply down on the bars to compress the front
Does the clunk sound like it's coming from the triple or does it sound like it's lower?
No clunking sound still?
Roll the bike back and forth and stab the front brake. Hear the clunk? Caliper tight?
Did you forget a wheel spacer?

[micoulisninja]

Originally Posted by csmith12

Sounds like you need to tighten up the head nut some more.

Do this;
Get a friend
Have the friend help you hold up the bike
You stand over the front wheel
Push sharply down on the bars to compress the front
Does the clunk sound like it's coming from the triple or does it sound like it's lower?
No clunking sound still?
Roll the bike back and forth and stab the front brake. Hear the clunk? Caliper tight?
Did you forget a wheel spacer?

what he said !!

[alex.s]

sounds like a cracked backbone

[Ninjinsky]

Originally Posted by MrSavvy

Also, after replacing the steering bearing, there's a metallic clunk on the front-end when going over a small bump of any sort.
.

I will say that my pregen does that, it continued to do it after I changed the fork legs so it beats me, worse when braking hard.
I have checked everything over the last 20 years and can find nothing, Neither can I "make" it do it by shaking the forks or bouncing the front up and down.
The "good" news is it never got worse

[alex.s]

Originally Posted by Ninjinsky

I will say that my pregen does that, it continued to do it after I changed the fork legs so it beats me, worse when braking hard.
I have checked everything over the last 20 years and can find nothing, the "good" news is it never got worse

it could be you only properly tightened the top nut that holds the top triple down, and you didn't properly tighten the nut below the triple. it is also possible that it is actually just the clutch or throttle cables getting stuck and then unstuck and snapping against something metal

[Motofool]

Originally Posted by MrSavvy

............After all of this, I just took the bike to Street and Trail to have them mount and balance the tires, double check the front alignment (on the fork/wheel/triple).

.........The problem I have is this constant, very rapid bouncing on the front-end. The mirrors bounce up and down by a milimeter or so, my arms vibrate a bit, etc...
It doesn't get better or worse with speed changes (as far as I can tell), or with baking.............

It seems to me that the perimeter of the tire is not concentric with the axis of rotation.

Two things may be happening:

• The good: The tire has been improperly installed and the beads are not seated all around. That is easy to spot, as the tire has a fine line on both sides that should keep a constant distant from the edge of the rim (around 1/4 inch).
  .
• The bad: The rim has been deformed radially during the accident. That is more difficult to spot, requiring a measuring process similar to the one for spike wheels:

http://www.dansmc.com/spokewheels.htm

The dial-gauge is not really necessary; a sharp tool fixed to the forks while the wheel turns freely will suffice.
Of course, you will need to keep the front end up in the air somehow.

[MrSavvy]

Thanks for all the info, guys! Busy week, reply soon.

[MrSavvy]

Thanks for all the help, guys.
I took it back to the shop after this thread was started. They inspected the wheel and deemed the wheel and tire are both perfectly fine. Also, they re-tightened the steering stem lock nut and the metallic clunk went away 100%. So that's good.

The ever-so-slight hop on the front end might just be my stupid OCD kicking in while riding.

Originally Posted by alex.s

sounds like a cracked backbone

I guess that is always a possibility. I just can't wrap my head around how a frame fracture could make a bike hop up and down. It seems odd, since everything else is in perfect condition.

Edit: Also, I can take my hands off the bars and the bike continues in a straight line. The front doesn't wobble back and forth. Even when slowing down from 40mph-10mph, those wobbles are gone too with the new tire installed. Also, just to clarify, the front end hop is so small it's more of a slow vibration of sorts. If that makes sense.

[csmith12]

So your good to go?

[MrSavvy]

Originally Posted by csmith12

So your good to go?

Yepp. Thanks guys.