I finally got my hyper 7 I bought used on ebay, everything works great, Spectrum Dx 2.0 radio, starter box, superbrain charger, 2- 7.2v batteries,glow pug ingnitor all for $300.00 . Everything including the buggy looks mint! Only problem is the Mach.28 engine has me chasing it around with tunning. I get it running good but then the idle starts to stay reved up after about 1/2 tank and the temps are climbing past 270 before I shut it down. I was thinking the lsn was to lean but still didnt help. I pulled the motor out to check for air leaks and seal it up when I noticed i can roll the flywheel over with my finger with little resistance! My O.S. .18tm in my revo is really hard to turn over with one finger. Question is , I guess this motor has hardly no compression left and wondering if this is what is causing the tunning problems and high temps?

The reason I ask is because I have not run a motor till it was dead yet and just trying to learn some of the symtoms that come along with it..

From your description i would say yes the pison and sleeve are worn out-high temps,inconsistant tuning and low compression.
The Macstar .28 does have a reputation for being difficult to tune but as you have little compression it rules out airleaks/tuning issues.

Ok thanks alot. I will just run it till its death and start searching for a good .21 engine for a smaller technical track.

Top or Rex 3 port, efficient, powerful, and they don't cost an arm & leg!

piston could be scored take it apart and check it.