Gy6 150 timing chain guide
 

I just pulled the head and cylinder off my scoot to diagnose a low compression issue ( piston skirt is scored ) and my lower cam chain guide came out. Do i have to split the case to replace the guide?

No you don't have to split the case. There are two chain guides, one is fixed and opposite the tensioner. This one is trapped by a relief in the cylinder just under the head mating surface. The one that the tensioner pushes on is held in place by a shoulder bolt that is accessed on the left side of the engine. Be sure the o ring is in good shape to avoid oil leaks. Caution! When installing the tensioner, fully retract the adjusting nose and install the spring and pin last. You should hear the distinct "click" noise of the tensioner extending to take up slack.

Chain guides
 

tried to get Picts but I'm computer challanged

Thanks Maddog, I'ts good to know I don't have to rip to far into it to replace the guide. This was a craigslist non runner I got for $135 showing 2300 miles ,with the title and my first gy6 150. It needs a cylinder(maybe just a good hone?) and piston and if I had to split the cases I was contemplating buying a new engine and using this one for spares and to eventually build it up with bbk and stroker.

Gy6
 

I've got a son in the business. Ruckhouse in Orlando. I've done lots of engine mods for him, everything from bored cases and stroked cranks to stock 50cc ruckus stuff. If you need hard parts give them a try.
With the price of new parts from China, I'd just replace the cyl & piston.