78 GS750 Cafe> forkswap done, but squirrely! Slow speed right to left gyro steer

[tweekin2]

Ok, time to throw myself down at the Cafe Alter.
I bought this project not running, with a CBR900 fork swapped on.
After several months of work, the mechanical part is done.
Well, today's ride left me puckered up.
I really don't know if the fork swap was done right, or if the wheels are balanced.
So I pretty much took my life into someone's hands on that one.
While riding around 25 mph it wanted to wander right and left.
It seemed like it took me to correct it to get it back on course.
Kinda like I had been drinking swerving around!
This appeared to go away when going faster, but my heart rate only took so much before I backed off.

I tried taking pressure off the grips to see what it would do, but I was shit scared to trust it.
Tire pressure is at 35 psi cold. I have taken the front tire off to take to a shop to check balance.
I will know more about that tomorrow.

While testing the turning and brakes, everything feels tight.
So what the hell is going on? Anyone else experience this?
Now, before you start telling m

e about rake, and trail, and all of the other geo things, I am just looking for some advice, as this is a project that I bought in boxes and not designed myself, I am not looking for a "scrap it" tone.
If you can't help, it would be appreciated that you move on to the next person to flame.
Thanks - Cory

 

[hillsy]

Steering head bearings are too tight.

 

[neevo]

Steering head bearings are too tight.

hillsy how do you get correct tension. I've always been told to overtighten slightly to bed in bearings. Then back it off approx 1/4 turn until the forks only just don't fall to either side under their own weight (with wheel off ground).

Is that even close to correct?

 

[trek97]

they need to fal side to side under their own weight. w tire off the ground.

copied and pasted from my honda workshop manual.

 

[hillsy]

neevo - you're pretty much correct. Most bikes bikes have a torque setting for the stem. You torque the bearings to this, then move the triples back and forth half a dozen times to bed the bearings, then undo between a quarter to half a turn until the bars gently flop from stop to stop.


Bearings too tight and the bike will not track straight - you will be correcting the steering all the time. It's a scary feeling.

 

[tweekin2]

Thank you all for the help! ;D
I have been riding for a long time, but this is my first project attempt.
The forks just were serviced, and the shop said they were in good shape.
I brought in the wheel this morning, and it was out of balance. The rim is straight though.
I am going to put the tire back on and ride it. If it doesn't clear up, I will tear into the triples.
I will follow your advise below very closely!

I also think I need to replace the rear tire.
The shitty thing is that this swap puts you in a pickle for tires.
I have a 130-70-16 Metzeler on the front. The rear is a 130-90-16 on a custom Lester mag.
I would like a lower profile rear tire, but I can't go any wider due to the brace for the rear brake.

I found a Pirelli tire in a 130-80-16 rear, but it says it is for a newer high powered scooter. It has a P speed rating, and I am pretty sure I won't be getting near that on this thing. This bike is just a scoot for quick rides and around town. Would ANYONE evern consider something like this?

Cheers - Cory

 

[hillsy]

You can "bend" the caliper brace out to clear a larger tyre - have a search over on GS Resources for wheel swaps (you can fit a 180 rear if you use an 1100 swingarm and a 17 rim....takes a fair bit of work though). I'd be thinking the scooter tyre would probably be OK though (they're cheap, so if it's crap you haven't lost too much $$$)

As for your front it would be nice to go down to a 120, but I don't think there is a 120 tyre for the Fireblade so you're kinda stuck with the 130. Unless you swap in a CBR600 17 rim.......again it's more work....