Front fork tuning question

[AndreP]

90 k75 rt with f&s “s” suspension
I’ve rebuilt them, replaced the steering bearings, and aligned them. My only problem left is a slight wobble on turn in and while leaned over still originating at the wheel or in one of the forks itself. This is especially noticeable when riding aggressively. I did notice that it disappeared, however, when I ride two up. So my tuning question. With the progressive springs in the front there is also a 1 1/4 inch pvc in each fork, do we think that’s the culprit? Too much preload?  Or is it possible that the increased pre load in the rear helped reduce the bouncing affect from the old suspension? For reference I weigh about 180 pounds without gear. I spent a long time getting my forks perfectly lined up and don’t want to pull them if I don’t need to. I also plan on replacing my rear shock with the ikon one from euromoto electrics soon.
Thanks!

[Duckbubbles]

First thing I would suspect is the front tire.  Sometimes the only way to eliminate that is to install a new one and see what happens.  Also, a good inspection of the wheel while you are changing the tire.

Frank

[Laitch]

Too much preload?  Or is it possible that the increased pre load in the rear helped reduce the bouncing affect from the old suspension?

Did you adjust the damper rod length in both tubes? Have you ever measured front sag? Which fork oil viscosity are you using. I think you're on the right track considering weight, if a defective tire isn't in the picture. The answer to these questions could shed some light on the situation.

[frankenduck]

Did you put the axle and wheel on before you tightened the four fork brace bolts?

[AndreP]

Fresh bel ray 7 or 7.5 weight oil
Aligned the front wheel using the axle test, if I loose ln the axle clamps and nut I can spin with my hand to this day
I’ve had a different (older) set of wheels and had the same behavior

Could someone walk me through front sag measurement

[Laitch]

Could someone walk me through front sag measurement

Did you adjust the damper rod length in both tubes?

[AndreP]

No I just left everything where it was in length.

[Kaos]

What was.the amount of oil added When you rebuild the suspension, 7.5, under spec or un equal filling could lead to sag and wobble when riding. When 2 up more weight is added making them more sturdy.
I believe in rest the sag is/should be 10/20 mm,, to about 40mm when sitting on the bike.
Maybe using /switching to 10 suits your riding style better
Front measurement can be done Balkan style.
Place the bike in the center stand, let your partner sit on the back, measure the fully extended suspension. Then measure it with just the bike standing with no stand and no rider/passenger and then again with preferably you sitting on the bike.
This could also be achieved using a scissor lift .

[Laitch]

Sag is something riders should understand. Our Bricks have the most basic type of damping because, as Henning says in the video, it's cheaper to make. It also is suitable for the type of riding done by most of us, so sag adjustment of the fork is not really necessary and not easy to do. To make our forks more responsive, installing emulators would be an improvement.

The image is of the dampers in the sport fork to which I was referring concerning adjustment. I guess we're beyond that. The first video discusses sag and the second is about emulators and their installation.

As Kaos suggested, changing fork oil weight could be all that is necessary to make your ride acceptable, although a rear shock with compression and rebound damping could also improve overall suspension performance.