A long time ago when I began to notice speed fluctuations on my VPI TT I cured it with a clean-out and lubrication of the bearing and a lubrication of the motor. So that might be an issue,
But phoenixengr, who apparently now licenses his inventions to SOTA, solved the problem forever initially for me and other VPI owners with his Falcon/Eagle/Roadrunner. Now sold together with a advanced design motor by SOTA. If they make it in a way that is compatible with your TT you might look into it. It's clearly the way to go for many reasons including better SQ, and it's quite low-cost for what you get..
But phoenixengr, who apparently now licenses his inventions to SOTA, solved the problem forever initially for me and other VPI owners with his Falcon/Eagle/Roadrunner. Now sold together with a advanced design motor by SOTA. If they make it in a way that is compatible with your TT you might look into it. It's clearly the way to go for many reasons including better SQ, and it's quite low-cost for what you get..