Motorcycle Repair: 67 honda CT90, valve clearances, bill silver

Question
Hi Bill, I recently obtained a sweet 67 CT 90 form an elderly friend of a friend who recently passed away. It has nice compression, but no spark. I've checked the points, changed the plug and battery. Headlight is bright. Every now and then when kicking it over with the plug out, I get a faint yellow spark, but usually only once. I haven't been able to put time into locating the condenser or coil yet.
I'm stuck. Any help would be great.
Thyanks,
Ray

Answer
Ray, not sure what you meant by "checking the points" but I hope you took the time to clean the contact faces thoroughly, gap them at about .014", then set the backing plate to where the points just OPEN at the F mark alignment on the rotor.

Ignition is battery-powered, so you should be seeing close to battery voltage at the points, when they are open. With clean points and 5-6v at the points, you should get a spark. Make sure your spark plug isn't fuel-fouled, which causes the spark to run down the side. If it has the original spark plug cap, it probably doesn't have a resistor in it, which is fine. If the cap was replaced, the resistance should be about 5k ohms with the cap off the wire.

http://www.cmsnl.com/honda-ct90-trail-90-k0-general-export_model17049/partslist/  The coil bolts up inside the frame, as you can see in this illustration, with the condenser attached. If the condenser has failed, you will see excessive arcing across the points as you kick it over. Coil and condenser failures are pretty rare, but do occur. Check primary wiring on the coil for about 4.5 ohm resistance.

Do check the valve clearances, as they are only .002" cold on intake/exhaust and are often forgotten.

Bill Silver