Rear mounted Friction Drive

1st time user. Glad to see such a movement happening. I recently purchased a rear mounted friction drive engine. The engine has a centrifigal clutch which is supposed to spin fast enough to expand and grab the housing of the friction drive wheel. The engine powers on but no movement from the wheel. There is no special switch or cable to expand the clutch so I am assuming that I am doing something wrong. I switched out the kit for another one but the issue is the same. I have had it accelerated for high RPMS for about a minute but still nothing. Does anyone have any suggestions? Also I have 20 front mounted engines that came from China. No installation instructions. Any suggestions on that too. Thank you..

I've attached pictures of the rear engine and I will get a photo of the front mounted engine. Thanks for any help.

Hear is the photo of the front mounted engines. Thanks again

I got 20 of those and 40 of the rear mounted ones. Yeah, I'd like to sell them and just keep one or two. I'll take $189. for the front and $179 for the rear kits. The fronts are a 1 package deal with gas tank already attached. I finally figured out the rear engine problems. They need to be run for a few seconds with the friction wheel off in order to let the centrifigal clutch pop out. I let it run that way and accelerated a few times and saw the clutch expand. I put it back together (only 4 screws) and found that it gets stuck if the housing is forced. The housing needs to be placed so that the friction wheel ALWAYS moves freely. I found that forcing the kit can pin the friction wheel so its important that the wheel always moves freely. If not, you have to loosen some of the bolts that hold the kit to the bike. I did that and have been having lots of fun. I also have about 50-60 of the 48cc mid mounted engines to sell. I am in Orlando, Fl in case anyone wants to come out to see them.