Ok, this is starting to drive me crazy. 2010 Quick 4 I put on an adjustable riser and now cannot get the shimmy out of the front end! Before you tell me to loosen the stem bolts and retighten top cap bolt-I have done that many times already. Just got on Youtube and it looks so easy. They are showing the problem I have(little shake in front end-forks etc.) and it is so simple to fix only it DOES NOT FIX IT...GRRRR! Bike is practically brand new. Any ideas? Is the top cap preventing headset bolt from doing its job as causing it to tighten before it should maybe? Thanks!

Take off the top cap and look to see if the steerer is at leas a couple of mm below the top of the stem. If the steerer is flush, you cannot adjust the headset. Either add another spacer under or above the stem.

+100

99% percent of the time that a headset doesn't adjust, it's because the top cap is bottomed against the top of the steerer and cannot push the stem or spacers lower to set the bearing.

Quick release tight? Do you have the head tube faced? It needs to be true and free of excess paint. And check spacers.

If he just replaced the stem, it's likely that the head tube is ok and the headset is seated correctly.

I vote for spacers.

Yeah, I'm guessing the top cap is bottoming out on the steering tube. The stack height of the new stem is likely different and could very well require an additional spacer, like a 2-5mm, to keep the cap from bottoming out when tightened.

I had the same exact problem and like the above posters, it turned out to be that I had no gap between the top of the steerer tube and the top of the spacer. Replaced the spacer with a taller one and I was able to tighten it up perfectly.

Before i replaced the spacer, i was able to tighten it down and it seemed to take out the slack but after a test ride, the shake would be back in the tube.

??

Front end shimmy could be a lot of things. This so called exact science of interwebs- remote- diagnostics- with no photos stuff.

threadless steerer tube extenders don't work well if the star nut is not straight even if you have the proper amount of spacers

As with most things, it's better to understand how something works and then ensure it's working the way it's supposed to rather than blindly aping a procedure.

Correct but it's worthwhile to check for obvious and frequent causes first before looking for obscure ones.

Yep. I went through the same issue on a bike of mine. There was not enough space between top cap and steerer tube. Add a spacer and I bet it works fine.

Thanks for all the input. Sure enough the riser/top cap is flush with the steerer tube. I will ad a spacer and report back.

Happy to say that I was 2mm off and the additional spacer solved my front end problems just like many said it would. THANK U!