That was an interesting ride, I see ya had some weather to contend with. Looks like ya had Fun
At the end of your Video you talked about the belt slipping, If it wasn't the wet weather making the belt slip
It's most likely the front belt. A new belt will fix that.
An adjustment of the front belt will tighten the rear belt. If ya need to adjust the front belt it's done by moving the engine forward.
This makes the rear belt pull on the front belt because their both attached to the clutch, which pivots and is under spring tension
But I bet all's ya need is a new front belt NAPA Gates V belt #4L290 while your at NAPA get a new rear belt too.
The Rear wheel can only go so far back in the dropouts because the chain can only be tightened so much.
In you Media pic
https://motoredbikes.com/media/img_4312-jpg.118068/ I see the 1" intake spacer on your bike but in your Video I don't see it on. I mentioned in your other post how to align and match the intake hole up better. I also mentioned about the Restrictor plate.
The restrictor plate is also a heat insulation plate to keep engine heat transfer from the carb
I highly recommend that you hog out the hole in the restrictor/insulation plate to 7/8" and reinstall it on the intake.
The 1" intake spacer was designed to move the carb farther away from the engine in order to keep the carb cooler.
I recommend that you use the 1" intake spacer.
I found that 1" was too long so I shaved my intake spacer down to 3/4" I also shimmed up my gas tank about 1/4"
because the carb cap cable guide was now hitting the gas tank. Shimming up my tank 1/4" also gave me more clearance for the electrical under the tank
As you can see my carb cap has a straight cable guide for the throttle cable
View attachment 170999View attachment 171000
If ya want an angled cable guide so it won't hit the tank Paul @
www.whizzercruzzerparts.com/product/carb-cap-with-angled-cable-guide/
BTW you got an Auto clutch and the One Way needle bearing needs to be greased with about a thumbnail of grease every 600 miles, If the needle bearing goes dry it'll ruin the needle bearing and possibly the clutch
Don't over grease it or the grease will fling out and get on the clutch shoes, Then your clutch will slip
I had trouble with the original auto clutch design so I changed a few things. In the future if you notice your clutch starting to eat itself alive. I can show ya some modifications on how to prevent that.
Tip; change your oil every 200 miles 40w
I've got over 40K miles on my Whizzer so I know what it takes to keep a Whizzer reliable
Have Fun