CT-4 magneto troubles.

The condenser can be checked by a mag shop. I don't know how to field test except by trading with another known good unit.
Are the bearings greased and in good shape so the gears turn well/easy?

First Check Those points again , Make sure they are absolutely Clean and set to 20 Thou , I use a can of CRC Electra Clean for doing this Work. Condenser sounds Most likely Your problem ,Do You have a Bright Blue Spark [ Needed ]or a Orange Type spark ? I have not been able find Condensers that fit the CM4/ CT4 ,But I have had 2 repacked and with Excellent Results . If condenser is OK then Next Suggest removing External Magnet at Check That . My test is to try and Pickup a medium size chisel or Spanner . If it is weak then Get it Recharged , and lastly if all else Fails remove Coil and have it Tested , May need a rewind .Someone able to do that Work Out here is a Bit had to Find , One Chap who did excellent Work passed on Recently .
If you can't get to a test Bench , Remove Impulse [you need a rattle gun to remove Nut ] and Put mag in a Vise and Hook a Drill onto shaft and Spin it over with a wire earthing to Vise. Hope this Helps you sort your Problem out . LJ

look real close at the cam the points cam follower rides on that it ain't pitted and wearing down the bakelite thus changing ur points gap.

condensers go bed over time, they can be purchased through most auto parts that order from standard electric. Not sure about the size as far as fit up.

If all else fails Roys magneto service in Mt pleasant is where mine go.