Hello all. I’ve been trying to find out why my front hub clicks back and forth on where it goes together at the front fork. I am referring to the slot in the hub and the recess in the fork. It may just be worn enough that it is just the way it’s going to be. Any insight on this issue? Just annoying more than anything. Just want to be sure I have it assembled correctly or am I missing something?

My RT-1B has .015" clearance between the backing plate groove and fork tab. Wonder if the RT-1 and RT-1B have the same backing plate and same fork tab width? Maybe you have a part mismatch? Do you have aluminum or steel lower fork tubes?

I think there was a difference in the slot and tab size between steel lowers and aluminum lowers?  At least on the smaller bikes.

Found below using AI. You can see the difference in backing plate tab widths, both types are on eBay. Hope this helps.

The difference between backing plates are the fork tabs meant to stop the brake assembly from spinning.
• 214-25121-00 (Early Design): Features a narrower brake slot. This is designed to fit the thinner, early-style locator tab welded onto early Yamaha DT1 / RT1 front fork sliders.
• 214-25121-01 (Later Design): Features a wider/deeper brake slot. Yamaha beefed up the anti-rotation locator tab on the newer fork legs to prevent them from snapping under hard braking, which required widening the corresponding slot on the backing plate.
• If you try to put a -00 plate on newer forks the plate will not fit. The wide tab on the fork leg is too big to slide into the narrow slot of the -00 backing plate.
• If you try to put a -01 plate on early forks: The plate will slip over the narrow fork tab, but it will have slop/play. Under heavy braking, the backing plate could violently twist back and forth hitting the tab, which may shear causing the front brake to lock up.

Early steel lowers on DT1 & i guess the first 360 had a narrow locator with corresponding narrow slot in the brake plate.
There's always 'some' movement although a tight axle helps making less noticeable.
Annoying when holding the brake hard on if pumping forks feeling for steering bearing play etc.
Could fabricate something maybe to sit in there but retaining it might be the problem.
I used to swing on my socket tightening way beyond specs but oneday i broke the circlip groove out where the speedo drive is retained.
I think there must've been damage in that area i hadn't noticed probably from someone attempting to get a frozen speedo gear off.
Never happen to any others of mine & still way over tighten them.
Yamaha also have a bad setup in the steering head too where the inner top race--the adjustable one--runs on the stem thread & said threads get flattened of especially if its been left a little loose for--ever--so end up with more than just running clearance & clicks back & forth with hard front braking.
One of my relics i was racing i hate to admit i bronzed the adjusting ring nut to the top bearing cone so it had no chance of moving.
But then a had to come up with a plan as the shield between bearing cone & adjuster ring didn't overlap when sitting on top of the adjuster ring.
Can't remember what i did now but it worked haha.