It's an old 91 KX250.  Mint and rebuilt in every way including wheel bearings and shock and swing arm and chain/sprokets.

I could have sworn I could feel this wobble while in air today.  I thought something was wrong and even stopped once to make sure I didn't have a flat or something.
So.  Put it on the $19.95 Harbor Freight lifting stand (don't recommend this exerisize.  I imagined it folding and letting the bike down and taking off.  I made sure to aim it away from the 300C and into the shrubbery.  Held my hand on the clutch....not like I could have stopped it.  Kinda like mom mom putting her little arm out over my chest when she had to panic stop the station wagon when I was a kid).

But, I put it in 3rd gear and it wobbled a lot.  Got the camera and only had it in second here in the vid.  But, you get the idea.

Maybe it's chunk of mud?
Chain to slack?
Just how they are?
Needs to be balanced?

Any input?

CooHead

The jumps I felt it on are mid third gear.  I know them as they are around my backyard track.

Since getting the rear shock professionally rebuilt, I have not messed with the clickers.  I have enough laps and familiartity with it now....today I clicked top and bottom softer.  Just for the heck of it.  Just to see if I could tell the difference.  That lap, first couple jumps, I felt it vibrating when reved off the lip.  Not like huge panic rev, but higher revs than the mid 3rd gear rev I left with.  So it was spinning pretty good.  Faster than in the above vid.  I swear first thing I thought was "wheel out of balance" feel to it.  No way....couldn't feel that on a dirt bike.  B ut it had the same harmics and frequency and equaled the tire spin.

So maybe the softer shoick setting alowed me to feel it?

I have felt the back wheel osscilate up and down when I'm in the air over fast jumps,  its not a nice feeling,  but it would be a pain to get it balanced every tire change

I believe we don't balance our wheels because we can true them via spokes. We balance car tires because they don't have spokes and you can't true them.

I have felt the same thing before on muddy clumpy tracks where chunks of dirt stick to the rim. The only thing you can do to minimize it (besides truing your rims) is to get the axle aligned as straight as possible and make sure there isn't any play in your linkage or wheel bearings.

You could also just brake tap on every jump

Edited by Tha Breeze, 31 May 2012 - 06:52 AM.

We balance dirt bike wheels primarily to counteract the out of balance effects caused by 4-5 oz single rim locks.

The rim lock is what throws the wheel the most out of balance. In dirt you typically will never feel an out of balance wheel like you will on the street. The focus on keeping unsprung weight down on a motocross bike is another reason why MX wheels are typically not balanced, as there is no way to balance them without adding weight (and quite a bit since you would be trying to counteract the rim lock). Offroad speeds are also considerably slower than speeds on pavement, and an out of balance tire typically doesn't start to become noticeable on pavement until you are above 45-50 mph. These are all reason why offroad wheels are typically not balanced.

It certainly doesn't hurt anything if you want to balance your wheel, however as soon as dirt gets on the tire or rim your wheel will be out of balance again so it is kinda pointless.

Edited by KJ790, 31 May 2012 - 07:37 AM.

Tha Breeze, on 31 May 2012 - 06:51 AM, said:

Out of balance and out of round are two totally different things, and cranking on the spokes is not a solution for a balance problem.

It is actually true that you could balance a wheel by moving it off center, but then it would be out of round, and while it would be fine while spinning free in the air, when running on the ground, the eccentricity will transmit the motion of the oscillating axle to the chassis through the suspension.  Not a workable solution.

I saw these "things" at the motorcycle shop you pour into your tube.  Weird little balls about 1/8 the size of toy gun bbs.... Suppose to somehow balance it. I don't know how.

Yeah after reading the posts after mine I realized I was totally wrong about what I said
Thanks for the clarification.

grayracer513, on 31 May 2012 - 09:05 PM, said:

Edited by Tha Breeze, 01 June 2012 - 03:47 AM.

KJ790, on 31 May 2012 - 07:36 AM, said:

perxactly

http://innovativebal...pe=MCAppInstall

englertracing, on 01 June 2012 - 02:30 PM, said:

Wow!  Can I get clear tires with those so I can see them spin when I stop?

Adammoto, on 02 June 2012 - 08:23 PM, said:

Yes. Let me find a link.