Weird wobble after front-end work

[d3vi@nt]

Just had the worn stock steering stem bearings on my ST2 replaced with a new tapered set. Had the shop rework the front suspension a bit, too; changed oil from 5wt to 7wt and added a bit of compression damping to cure the front-end dive on braking.

Suspension feels great, but when riding a straight road around 40-45mph, the bike does a mini-slalom on its own. Meaning a minor weave, left to right, right to left, smooth and rhythmic as if on autopilot. Not noticeable at lower speeds or at highway speeds up to 80mph.

The day I rode home from the shop was incredibly windy, coupled with the upgraded bearings made me think (hope) it was just an anomaly. I checked the rear wheel alignment and measured the forks best I could to verify one wasn't higher than the other -everything looks good to my eye.

I need to ride it some more to check my head, but wondered if anyone had any input or suggestions on things to check?

Thanks in advance.

[MotoPsycho]

I'm curious if the stiffness in the front end from the heavier oil and increased compression made tire pressure more critical.

[Howie]

First thing I would check is head bearing adjustment.  Oh, and tire pressure.

[Bill in OKC]

Agree,  -- recheck the head bearing adjustment.  I put tapered in my Monster and they loosened after a few miles.

[brad black]

do the steering head bearings have seals that drag?  sounds a bit like an ohlins steering damper when they get a lot of stiction.

are the forks diving because it has std springs?  they're too soft, and have too little preload, even with the adj at max.  you need at least 20mm more.  if the rebound adjusters are open at all, the compression adjuster are pretty much redundant.

[d3vi@nt]

Thanks for all the replies thus far.

A few more answers; the new bearings are the SpeedyMoto tapered kit, but I have no idea how to tell if they have seals that drag, but they feel smooth. I don't know how to tell if they're adjusted properly, either, so I'll have to figure that out. And I don't have the tools. I can say they felt a lot better than previous --no more harsh feedback over bumps and much more sensitive to steering inputs.

The springs are stock, but the shop added preload shims (20mm), set sag and adjusted for weight this time around. Much better feeling and handling.

For tire pressure I run Ducati's (frame sticker) recommended 32.7/36.9. I'm running Michelin PR2's and Michelin recommends following Ducati's recommendation. I just verified the front at 32psi cold, so no change from normal.

At this point, I'm not sure about the previous oil. The shop said it was 5wt and they replaced with 7wt. I looked at my old receipt for the previous work about 2.5 years back and they show that they put in 7.5wt then, so in theory there was no change in oil weight between then and now.

Thanks again for all the input. I'll try to check on the bearings.

[ducpainter]

Prolly no huge difference.

run 34 in the back.

[hackers2r]

What about the rear shock?  Did you adjust sag and compression accordingly?