89 Katana 750 High speed "shake"

[Murph]

Hello everyone, new to this site but not to bikes, Just rid of my ex500 and picked up the 750 Katana. Went out for a ride today got out on the high way, The bike handled pretty good around town, plenty of power compared to the EX500, so when I got out on the high way I brought it up to about 100 mph and got some shimmy or shake in the front, which got progressivly worse til i shut it down around 110, not that I travel at these speeds daily but you all know the desire to twist it back a bit. When I got home I took a look at the tires, the previous owner put a new set of perelli's on it about 1000 mi ago. As I looked at the front tire I noticed that it appears to have a raised flat spot almost like someone has wrapped a belt around the tire. So I'm trying to figure out what is causing the shake, anyone know why the tire would have a flat spot like that with such low mileage on it? Any Ideas why it might be shaking? It appears that the tire weights are all on the rim. Any help would be great...

Eric

[JetDoc]

The flat spot could be causing the shake.

Any chance the bike had been strapped down for an extended time? That would explain the "belt wrapped around the tire look"

If it were me... I'd replace the tire.

[Murph]

The bike was strapped to my trailer for about 2 hours in transit to my house but that's it.... hate to buy a new tire but figured as much

[Slofuze]

Could the previous owner have put the binders on? Is there a flat spot on the rear as well?

[BIGKAT1100]

I have an 88 1100 Kat and just got shed of that issue by replacing the fork seals. Other things to check would be:

1. check tire pressure (always start with the easy stuff)

2. front tire out of balance

3. make sure front rotors are true

4. raise front end of your bike and check for play in your steering head by grabbing the front tire and pulling on it feeling for any play. This can be corrected by tightening your steering head bolt

By your bike being the age that it is, I would lean more toward steering head having some play in it or the fork seals. Mic your rotors to make sure they are in spec because if they aren't, they won't dissapate heat correctly possibly causing them to warp. My rotors were true but I had to do the other stuff and it made a huge difference in handling and stability at speed. I was getting a head shake @ 105 mph after checking those items, I'm steady all the way up (well 130 mph anyway).

[Murph]

Could the previous owner have put the binders on? Is there a flat spot on the rear as well?

The tires don't have just a flat spot it goes all the way around the front tire. I have checked the pressure and its at 35, the fork seals don't weep, but i'm not sure if that's what you were talking about BIGKAT I guess I could drop the bike at the shop and have them take a look at the rotors and have them balance the tire, I'm pretty sure they are going to tell me to get a new tire UGG I hate paying bike shop prices and it will errk me a little as the tire only has 1k mi on it, but I can't think that having a flat spot all the way around the front tire is helping. I took it out again today and it seems true all the way up to 100 then I get the head shake.........
BIGKAT by the head bolt your talking about the one right on the top that is right above the gas tank correct? And to tighten that I would just ratchet the hell out of it??

Thanks guys for all your help

Eric

[Murph]

Here is a shot of the front tire you'll see what I"m talking about with the flat spot


Eric

[allblackkat]

looks like a tire that's only been going in straight lines... How old is the tire?

sorry, just re-read the initial post... 1k miles....probably all in a straight line...

[hardlydangerous]

I have an 88 1100 Kat and just got shed of that issue by replacing the fork seals. Other things to check would be:

1. check tire pressure (always start with the easy stuff)

2. front tire out of balance

3. make sure front rotors are true

4. raise front end of your bike and check for play in your steering head by grabbing the front tire and pulling on it feeling for any play. This can be corrected by tightening your steering head bolt

By your bike being the age that it is, I would lean more toward steering head having some play in it or the fork seals. Mic your rotors to make sure they are in spec because if they aren't, they won't dissapate heat correctly possibly causing them to warp. My rotors were true but I had to do the other stuff and it made a huge difference in handling and stability at speed. I was getting a head shake @ 105 mph after checking those items, I'm steady all the way up (well 130 mph anyway).

Yeah pretty much what he said

Start with the tire pressure.

Make sure the fork adjustments are the same, and best to start with the factory settings. Same with the rear shock. I'm not sure if the pre shocks were adjustable but if so set if back to stock. Also make sure the forks are set the same height in the clamps.
Front and rear suspension settings that don't work with each other will cause aweful balance and handling issues.

If the tire was balance using stick on wheel weights make sure you have some on either side of the rim to balance it out. all the wieght on one side can cause a shake as well. I would recommend replacing them with clamp on type and attach them to the center rib on the wheel where they should be.

replace your fork fluid and replace the seals if leaking. Uneven fork fluid can cause handling issues.

check for wheel or steering bearing play

[FastJetta97]

yeah that tire looks fine to me... just hasn't been leaned at all...

i would say prolly vibration from out of balance rim and tire.... i wouldn't rush out and get a new tire at all... try gettin it balaced first for sure....

[BIGKAT1100]

BIGKAT by the head bolt your talking about the one right on the top that is right above the gas tank correct? And to tighten that I would just ratchet the hell out of it??

Thanks guys for all your help

Eric

1. The front tire looks fine, it just has a "squid trail" running thru it. Never hurts to have your balance checked though. If you're not getting any feedback thru your brake lever, I wouldn't worry about the rotors.




2. If you have "slop" in your steering head, here's what you do. Loosen top bolt (#9 in the diagram) and make your adjustments using item #5 (clockwise to tighten). Snug it up just enough that the fork doesn't flop one way or the other when the front wheel is off the ground (on the center stand).

Between getting the tire balanced and checking and adjusting the play out of the front end, that should sure you up.

Hope I was a help to you and good luck.

[Murph]

thank you so much I guess I got some fun ahead of me this weekend, but isn't it all fun ..........again thank you all I'll let you know how it turn out

[kat6hundo]

good info to have, I got a quick question in regards to the forks, at the top of my front forks I have 2 dials that go from 1-3 it's my first bike, and i'm assuming that's like some kind of minor adjustment to your front suspension? Dude I bought the bike off had no idea what they were either. If you need pictures, i'll get some tonight

[BIGKAT1100]

thank you so much I guess I got some fun ahead of me this weekend, but isn't it all fun ..........again thank you all I'll let you know how it turn out

That whole steering head tightening thing shouldn't take anymore than 30 mins and that includes putting it on the center stand, propping up the front wheel, and testing it to see if that even needs to be done.

good info to have, I got a quick question in regards to the forks, at the top of my front forks I have 2 dials that go from 1-3 it's my first bike, and i'm assuming that's like some kind of minor adjustment to your front suspension? Dude I bought the bike off had no idea what they were either ...

I think those are dampening adjustments. I think you want to make sure they are on the same number. Heck, test ride ther bike on the different numbers and see what you notice. I always run my bike suspension adjustment on the stiffest or highest settings but to each his own, ya dig.

[tone]

The ajusters on the forks are for rebound & compression damping, start of by either trying to find the stock settings & work from there one ajustment at a time untill it suits you, test between ajustments & if its worse go back

someone here will be able to give you the stock settings i'm sure but if you cant find the stock settings turn them all the way in then all the way out till you know what the middle setting is & start from there

badly ajusted suspension can cause the symptoms you describe, its usually worse if you are either a lightweight fella & they are wound all the way in or a fatty with them wound out same on any ajustment on the back shock

check for play etc too as described by bigkat1100