Flex tape, motorcycle rim ?

Replace the wheel with one designed to accommodate a tubeless tire.

Trying to seal a spoked wheel, designed to be used with a tube, is going to become an exercise in futility. The first time you need to adjust a spoke, the seal will break.

Also, most tubed wheels do not have the kind of bead required to maintain an adequate seal for a tubeless tire.

The tubeless tire for the trike is a bit larger diameter than the tire for the spoked rim. I'd like to keep the original fender which is different. It looks like it's time for a tape measure to see how much space there is between tire and fender now. I haven't compared the other parts yet. This site

Dean, you've been posting on Reeky since at least late 2001. You've read all the threads about fitment, and, while I'm not saying it's not a good thing to revisit these memes from time to time -- just to keep up to date so to speak, I'm saying it's plain we have nothing new to talk about here w.r.t. motorcycling. For example, it's been plain for some time that catastrophic decompression of the rear tire does not necessarily result in immediate loss of control, while catastrophic decompression of the front tire does. Now, there may be reasons to risk it: conforming with fashion and style in chopped bikes, for instance, which might lead you to choose rims and tires that are less-than-compatible and even a little dangerous to use with any frame geometry you could name. But saving money is not a good reason.