When you are ready to install the motor and the frame is cleaned up, you can lay the motor on its side and place the BARE frame over the motor, slide in your mounting bolts and then tilt the frame back upright.
Install the other components AFTER you do this.
I have heard about doing that to get it out.Makes sense it could be the same to get it in.As I learn these bikes tips will make each task easier and simpler.2 things I learned.The bundle of wires coming from the rotor area go through the opening behind and around the airbox area through the battery box and one connector is attached to the positive side of the solenoid.Also I learned the small screw on the oil pressure switch is a soft headed strippleable screw that won't come out.I bought a set of jis screwdrivers to prevent that.They work great, but not on this crappy screw.I cut that wire for now.Also, my manual said to remove the clutch and rotor assembly.While that might remove some weight it certainly isnt necessary.I also found the bolts holding the back of the mufflers to the frame break easily.I also used a piece of allthread to tap the long through bolts out after they came out about halfway.I have rebuilt ford 289,chevy 327,350,dodge slant 6,and one 40 hp volkswagen,one suzuki gs 1000.They were all easier to get the motors out of.These bikes have almost no room between the motor and the frame,and between the airbox and the rear of the carbs. I also do not like the way the head bolts are down in a tunnel.If you snap one of them you're screwed.I suspect they are hard to break.
But aside from these design flaws the single cam is a huge plus.And the set screw lock nut valve adjustment is huge too.After much trial and many errors I got to where i could tear the suzuki down to the crank in just a few minutes.It had a roller bearing crank instead of plain bearings.Those cranks could withstand a motor being built to 300 hp.I think the honda 4's are probably pretty robust also.The biggest pluses of all is there are about a jillion aftermarket and NOS parts for these bikes.The parts listed as obsolete are still easy to find on ebay and some on craigslist.
plus every guy I have talked to about my working on this bike says wow, I remember those, those were cool bikes.They are still cool bikes.