I have a Modolo stem on my Trek 660 that I haven't really missed with since I installed it 15 plus years ago. I was working on the old Trek and wanted to adjust the bars. The stem has an allen bolt that runs up through the bottom and then screws into some kind of circular slotted nut. I was only able to turn the bolt about 1/4 turn. The nut turned with the bolt. I tried a to hold the slotted nut steady with a screwdriver, but the bolt still wouldn't budge.

Before I get out a bigger hammer, can you refresh me about how this system is supposed to work.

Thanks

Hi, I have one of these and I can walk you through it, but first, just explain what adjustment you need to do - rotate the stem/bar in the fork, raise/lower the bars, or rotate the 'bar vertically to adjust the bar angle?

I'll be able to get back to you later tonight, if someone else doesn't chime in and solve it for me.

Thanks! I just want to change the angle of the bar.

so it's the bar clamp you want to loosen, right?
a single picture would be worth 1K words, since I have no idea what the specific hang-up is from your description.

5mm allen wrench from the bottom. You shouldn't need to mess with the top. Turn CCW (facing)like any RH thread.

Drench it in PB Blaster if it's stuck.

It is done. Thanks