Steering issues

[cronos68]

Bike-Pre 600 20k miles, Tires properly inflated with about 30-40 % thread left. Race tech 1.0 springs. Shock is stock. Steering turns fine side to side with no notches or rough spots. Top bearing in triple tree was recently greased with same vague characteristics. Fork oil shows no leaks at seals. Fork oil could be original.

Symptoms
steering is vague as bike drives, more noticeable at lower speeds. More noticeable as bike warms up
Feels like bike is continuously correcting its self.
seems to want to go left (not sure)
bars move fine side to side but when driving they seem tight (like triple is too tight)
like driving on a narrow peak and bike keeps trying to stay on?
Also temp driving was about 40 deg on the drives

Fork oil possibly lower in one fork leg?

Any advice would be great.

[maniac1886]

Is your rear tire in alignment?

[Kreylyn]

You put front springs in, but did you do anything with the stock rear shock yet?

Krey

[cronos68]

shock is stock, was gonna replaced with r6 shock when I get it. The shock has very slow rebound rate and is obviously showing age. Would this be the blame.
Rear is aligned. Thanks

[steves]

Could just be an old cupped tire too

[cronos68]

The problem increases as the bike is driven. Its not as bad on start out.
The front has decent thread left but does show signs of flattening. Its not badly cupped though. I've had badly cupped and also worn tires that never handled like this.
But if the tires were very narrow and peaked I feel this is a good way of describing sensation, bike feels like its searching for balance. Thanks

[TRPUT]

I'd start with new fork oil at the right levels. A squared rear tyre will cause those handling characteristics.

[Kreylyn]

shock is stock, was gonna replaced with r6 shock when I get it. The shock has very slow rebound rate and is obviously showing age. Would this be the blame.
Rear is aligned. Thanks

The problem increases as the bike is driven. Its not as bad on start out.

Handling is greatly affected by the rake. The higher the rake = slower and harder turn in but more stable. The less the rake = faster quicker turn in but less stable.


There is a range in between excess where you can have a quick but fairly stable turn in these bikes. They are very forgiving this way. Even at stock heights, your suspension can cause variances in the rake.


What your describing fits exactly to my initial thoughts on probably cause.


With new and improved springs in the fork, your front end is no longer dipping excessively low as the stock suspension will. Especially after age. This means the front of the bike stays higher on avg.


The rear shock with a slow rebound may "stack" the compression. Meaning it does not fully rebound at all when your riding the bike, especially with repeated compressions from hitting the curves or rough roads that use the compression a lot due to bumps/pot holes. As the rear compresses the rear of the bike drops over time. It hangs lower on avg.


lift the front, lower the rear = greatly increased rake. Just a couple of mm can make a huge difference.


Simple test at no cost and just a couple of mins to set up... drop the front end by raising the forks .75" through the triples in the front. Go for a safe but reasonable test ride. I'll bet you see a huge improvement in handling, and a large decrease in the problems you noticed if not gone completely. At least at first anyways. If the rear spring is compressing too much, you may see them come back some as it drops the rear on the ride.


If that does turn out to be the case... replace the shock. If you use an R6... keep in mind that shock will lower your rear by 3/4". You will need to adjust the front end the same drop. The above mentioned adjustment is not the same distance though due to the angle of the forks, and you should never move the forks more than 3/4" up in the triples as you do not have clearance for more for the lower triple/fork lower tops.


Krey

[cronos68]

Krey, I think this maybe it. After looking at this again I can see the rebound is very slow on its return. Taking quite a bit longer then my other bike (VFR 750). I don't remember it this bad or taking this long to return up. This might explain why the ride deteriorates as it gets longer. Most noticeable between 30-50 MPH. The shock is 20+ years at this point.
So because the geometry is off the bike is searching for its line? This would make sense.
I'll try dropping the tree down to see if that helps. I know the shock is shot and will get replacement, just didn't know if the shock was the culprit.
I tried driving at 40lb PSI in rear had no noticeable effect.
Tires have no adverse wear on them at this point either.
Thanks

[cronos68]

Update. Replaced shock with a 97 1200 bandit shock i all ready had. Same issue. This shock is old but was hoping to get some noticeable difference with the weaving. It turns in better but still searches for line. I'll measure the tires as I don't see anything that obvious other then the milage wear. No fork oil leaks.

[Kreylyn]

Update. Replaced shock with a 97 1200 bandit shock i all ready had. Same issue. This shock is old but was hoping to get some noticeable difference with the weaving. It turns in better but still searches for line. I'll measure the tires as I don't see anything that obvious other then the milage wear. No fork oil leaks.

I don't have the numbers in front of me atm, but as I recall... the gen 1 B12 shocks were the same length and stroke (almost identical shock actually) to the Kats. I would expect no change at all by swapping the shocks if that is correct.


*edit* Bit of looking around and found these numbers online...

Gen 1 B12 Shocks are 300MM (11.8") Long with a 64MM (2.5") stroke
Pre Kat shocks are 298mm Long with a 59mm stroke.

The minor improvement would be the very slight increase in length may be pushing the tail slightly taller to start with, but again... the age and design of the shock may be putting you right back into the situation of the slow rebound and it compacting on it's self and not tall enough to start with for the new spring setup on the front.

Krey

[cronos68]

Yes the shocks look identical and swapped in easy. My thought was the original kat shock was rebounding very slow and perhaps sits to low now effecting the geometry. So even though the bandit shock is the same it shouldn't sit as low (under load) and might stop the weaving. Trying to eliminate what is not causing problem.
But drives the same. I will drop the tree slightly.
Also i've driven over 7K miles on new springs (forks) and this issue began under 500 miles ago.
Thanks

[maniac1886]

I've heard around here that dropping the front end a little bit helps greatly too. I dropped the front on mine about an inch and put the busa shock on it. The busa shock lifted the rear 2 inches and with the one inch drop in front, it does turn a little harder, I cant get as low in the twistys i've noticed too (or at least I dont feel as low). If it were me in the position (im no expert) but I would try dropping that front end down 3/4 of an inch and see what that does. Like I said I dropped mine an inch and in the big bumps, the bike would hit the front fender a little bit so dont go farther than an inch. I took the fender off my bike tho so its no longer a concern of mine. food for thought.

[surefoot]

make sure the alinement notches are correct on rear tire.