Front End Wobble

[gvkohl]

I just purchased a used 2002 Katana 600. The bike is in good shape. Some small scrapes on the fairing, but no real damage. It runs smooth and I love riding it.

I do have one issue. There is a bad front end wobble at around 40-50 mph. You can feel it slightly when riding. It is not as noticable in acceleration. If I take my left hand off the grip it is more pronounced. If you take both hands off the grips, you may go down. I did that once at around 40 mph as I was slowing down and the wobble became violent.

There is no cupping or odd wear on the front tire. The previous owner states that the wobble has always been there. He had worked with Suzuki and a dealer to get this corrected. He says it had gotten better at one time after steering bearings had been replaced and after the front wheel had been replaced.

I would like to get rid of this issue. A co-rider with a 2000 Katana 600 does not have this issue at all, so I know it is not normal for the Katana.

Any help would be appreciated.

[steves]

Wheel out of balance? Messed up forks? Bad axle? Maybe a http://www.barsnake.com/

[tzortn]

This thread may be useful: http://www.katriders.com/forums/viewtopic.php?t=23454&

A resonance around 40 mph is not unusual for motorcycles. If everything checks out mechanically (tire wear, head bearings, wheel balance etc) and all you need to do to get rid of the wobble is put your hands on the bars you should be ok.

[TheKlic]

also check shock preloads.

[loudnlow7484]

my old gsxr use to wobble around 140..... but at 40? I'd say there's something wrong.
Check all your suspension settings.
Lift the front of the bike, and spin the front wheel. Check for wobble/bends from the front, and from the side. Check your rotors, too. Wiggle your front wheel, to see if it is sloppy on the bearing. Push your forks front to back, to see if there is play in the steering head bearings. Look at your front wheel from straight ahead, make sure the wheel is centered between the forks.
Now lift the back end. Check for play in the swingarm mount, the shock linkages, etc. Check your rear brake rotor. Just for kicks, check your chain for stretch and for slack. Make sure your rear sprocket is straight.
If all that checks out, take it to a place that straightens motorcycle frames.
If they can't fix it, sell it and get another.

[Jax]

What about wheel balancing?? I believe my rear wheel has a small weight on it and there is that balancing powder...not sure if it applies to the front wheel but worth looking into...

[Chuckwick357]

I had a little wobble last year, but I went away when I got new tires and had them balanced. It’s seems to be coming back. I figure the front tire hasn’t been balanced in like 5-6k. new rear tire 1500k ago. it’s not violent though, and I can’t feel it unless I take both hands off the bars.

[meanstrk]

Tire pressures, balance or cupped tires.

[loudnlow7484]

I didn't mention tire balance or cupping because that just didn't sound right to me.

My front tire is currently way out of balance, but it does more of a bounce then a wobble. Wobble to me sounds like a tank-slapper kinda effect, or like the front wheel on a shopping cart.

And even with pretty cupped D208's on my last bike, I could take my hands off the bars completely and not have any shake or wobble.

[DoyleDee]

I'll be willing to bet it is the tire itself. I had metzler's on mine and had to put my stand by tire on the front---had a bad wobble when I took it off (went to metz's front back) and still has a wobble now. It has no sign of cupping and still has about half the life left in tread. It say get new tire(s) at least the front... I know some will say don't mix front/back with diff brands...but I have no issues with mine except the wobble... until cash flow is better I'll do what I have to.

[The CyberPoet]

Common (overlooked) causes:

Previous owner wheelies or wrecks into a curb. Replace axle bolt and front wheel bearings, steering stem bearings.

Small fall bent one handlebar. Imbalance in handlebar bends results in steering system imbalance that translates into harmonic vibration at specific speeds. Unbolt handlebars and lay atop each other -- they need to be perfectly identical in bend (if in doubt, replace).

bar-end weights uneven, or retaining bolt bent. Same effect as a bent handlebar extension tube.

Brake caliper piston not retracting as it should; pad rubbing caliper. Check for free rotation, rebuild brakes as necessary. Include rear brake during checks, as it can affect the front as well.

Rear chain alignment off, meaning rear wheel alignment is off. Result is a slow weave that induces instability at speed.

Fork oil levels uneven, fork seal condition bad, fork tube bent minorly, or fork damping settings uneven. Reset fork settings, retest. If settings even, replace fork dust seals, oil seals, oil, and inspect tubes while disassembled.

And then there's the obvious ones:

Tires not balanced. Rebalance.

Tires worn excessively unevenly. Replace.

And in no case should you get a significant wobble at that speed. The real question is whether the wobble is repeatable at the same speed in a different gear (different RPM band), and whether it repeats at exactly double the speed.

Good Luck!
=-= The CyberPoet

[gvkohl]

Thanks

Thanks to everyone who has replied. I am going through and checking everything eveyone has suggested. I will keep everyone updated on my progress.

[xxFrYxx]

good thing you kept us updated..........sounds like a slightly bent rim

[reconstyle]

A bent rim would wobble at all speeds....

[jgalar]

I have an 01 and it does the same thing.
I've recently replaced wheel bearings, rebuilt the forks, adjusted the steering head bearings. No change in shake at 40-45mph.

I just mounted and balanced a set of conti force tires and the shake at 45 is gone - now its at 30-35.

A change in the shock preload setting may help by changing the weight on the front end.

I just keep my hands on the bars and don't loose any sleep over it.