Motorcycle Repair: 79 honda cb750k low compression, honda cb750k, milage

Question
I picked up a 22k mile 79 cb750k...cleaned the carbs starts well, however one cylinder shows 90 for compression, 2nd one in from the left. The others are 150,145 & 145. I was going to run a tanks full of gas and seafom and see if it a carbon issue, but whats the chance of that? and where would you start looking?

Answer
Art, there's a simple trick you can use to figure out if it rings or valves.  Pull the plugs and squirt a little oil in the cylinders.  Not too much or you can hydraulic lock the engine and it will bend a rod.  Just one squirt from a oil can.  

Open the throttle open full, and check the compression again.  If the compression comes up it's leaking past the rings and if it doesn't, the valves are leaking.  If the like has been sitting a while, it's possible the rings are stuck.  It's pretty low milage for the cylinders to have much wear, unless it's been over heated or run low on oil.

Regards
Rich