High Speed Weaving Problem.

[racer11]

Any help would be appreciated,

So I just bought my 1996 750 Katana about a month ago. It rides really nice at anything under 60 mph. As soon as i approach anything higher, the bike starts to do a slow weave or wobble even. It feels as if the rear is moving side to side kind of. It is very uncomfortable on the highway. I then looked at the rear axle adjustment tick marks and noticed that the left and right side were not in the same position. So I set them to the same position and that seemed to help the problem a little but it did not fix it. I took the bike to two different shops. The first said that the rear tire is probably not in line with the front and i should keep adjusting the rear axle in either direction until the problem goes away. The second shop says that i was riding with the tire pressure too low and the tires are now shot and i need new tires. Could low tire pressure cause this type of issue? I only rode the bike a few times since i bought it and I didn't check the tire pressure so it could be low. Please let me know what you think. Thanks.

[catfish]

are your tires out of balance? i'd put new tires on it if they are old or misused

running tire pressures too low is very dangerous, and you should check your tires regularly, regardless

[racer11]

the tires are not out of balance cause that would cause a vibration. it really is not a vibration. the tires are dunlop qualifiers that have plenty of tread and are new. i have the receipts from the guy i bought it from. i didnt check the pressure since i bought it and i rode it probably 100 miles since. i felt them by hand before i started riding and they seemed firm and fine. maybe i ruined them?

[albuKat]

On the opposite end of the bike... check the steering head to make sure it is firm with no side to side play. If theres play in it, adjust the jam nut tighter. That could cause a wobble. Do that, and make sure your rear tire is in alignment (should be able to tell by looking at the chain) How low was the air pressure in the tires? If they were still firm when you checked them, I doubt you ruined them, but air presure is something you should check EVERY time you get on to ride, along with oil level and chain condition.

[abacaxi]

2-3 cans of beer has been known to cause that problem.

[albuKat]

2-3 cans of beer has been known to cause that problem.

haha.. didnt think about that one!

[tzortn]

I have been told to never trust the hash marks on the swing arm alone. There are articles on the web on how to do your alignment using string (http://www.motorcyclistonline.com/ho...els/index.html). Another option is that Motion Pro makes a tool that you clamp to your sprocket and it has a rod that you use to gauge the angle of the axle versus the chain (http://www.motionpro.com/motorcycle/...lignment_tool/). Or you could just eyeball it.

[DumbLuck]

dont go back to that first shop if they couldnt take not even 5 minutes to make sure your back tire/sprockets and chain are all in alignment, and tire pressure up to snuff. a loose neck is easy to check if you have a center stand, and someone to hold down the back of the bike

[racer11]

thanks for all the suggestions. i will try them as soon as i can. and i will be sure to check my tire pressure from now on!

[Honorabledog]

I second checking the steering head bearings. Also look for any loose bolts or nuts throughout the entire bike and also the fairings. I had a lower fairing bolt come loose once and it would get squirrelly at higher speeds cause of the wind.
Is this a violent wiggle or just wiggles enough to get you uneasy. My 750 conversion wiggles slightly at 70-80 but then gets smooth as I get to 100. Bothered me at first but now I adjust and push through....nothing beats that slight nervous heart pounding adrenaline rush

[racer11]

it is not a very violent wiggle. Kinda slow back and forth but it feels like the rear is moving quite a bit side to side. It's probably only wobbling an inch or so but it feels like a lot at 80 mph. As the speed increases, the wobble seems to get faster and more uncomfortable. I am able to ride the bike at 80 or 90 safely but this motion really takes a lot of the enjoyment out of riding. I am not able to check the bike for a few days since I am away from home but when at the first shop I went to, we checked the front of the bike and everything seemed fine. I will check again maybe I missed something.

[customcracka]

Are you sure the rear wheel is good and tight?

[Honorabledog]

No doubt if the wobble gets worse when accelerating then do not accelerate through this. Double check the alignment, if the steering stem nut is tight make sure the adjuster isn't TOO tight as this can cause the stiff steering at speed, and you know the tires are good. Maybe fork oil low in one tube? Makes the bike dip at speed more so on one side than the other creating a wobble. Seen this on the track, not really on the street yet. Also have you adjusted the sag on the bike to your specific weight? Alot of variables when I can't see the bike.

No matter what use caution till we figure this out. If she decides to jump out from under you it's quick and sudden and certainly not something we want happening at 80mph. I had a high speed wobble on a friends FJ 1200 back in 91 and I had to buy him a new bike