As you can see, I have a Hyper 7 Mach .28 like you do. Look at the sheet that came with your Hyper 7, it is a sheet about the Mach .28, and it tells you the break-in procedure. If you follow this, it will be fine. Just make sure that the piston is at bottom-dead-center (BDC) when you shut the engine down or when it shuts down after running out of fuel. You should also make sure the engine is at BDC after running your Hyper 7 anytime, even when break-in is finished. The Ofna manual also has a break-in procedure.

If you do not have a temperature gauge, Get one!! I can't emphasize how useful this tool is! Get an infra-red gauge like duratrax flash-point, HPI makes one, others make them. It's about $20 but it is worth ALOT when it comes to tuning and protecting your engine. You will want ur engine to get up to 210-225 degrees during break in. You never want your head-temp to be over 250 degrees as it says on the Mach .28 sheet. If you notice ur engine getting too hot during break in, ur mixture is too lean. If it is getting above 225 degrees or so, richen your mixture. IF you find the engine has gotten too hot, shut off the engine and let it cool for 10 min at BDC, just like you normally would if the engine had run out of fuel.

You can feel where BDC is when you pull the pullstarter and then suddenly pop! the piston goes down. Then it is a bottom-dead-center (BDC) Make a mark on the flywheel so you know where BDC is.

Switching off your car will only turn off your receiver = very bad idea if your motor is still running.
The best methods to turn off your engine are 1. Pinch the fuel line close to the carburator (like within an inch or 2 is fine). 2. Put a piece of wood against the flywheel (do this from the bottom of the buggy). The second method might be easier since ur hand isn't next to a hot motor and ur motor won't rev up some when you shut it off like with the 1st method.

If your still not sure what ur doing, then just take some time to read your manuals, read stuff online; there are plenty of how to's including motor break-in. Also, don't be afraid to ask questions, we are here to help.