Motorcycle Repair: 1970 Honda CT70, honda ct 70, stator assembly

Question
I have a 1970 Honda CT 70 that has not run in many years. I recently replaced the carb, stator assembly, points, and spark plug.  I do have fire to the plug and gas to the card and the air is clean but it still will not start.  Could this be a timing issue?  Also, does the battery have anything to do with the actual operation of the motorcycle or just it just operate the lights etc.  Any help will be much appreciated.

Thanks

Justin

Answer
Justin, the points have to be set to open at the F mark for proper ignition timing, so make sure that is happening first.

All the little 50-70cc bikes have magneto ignitions, which are not dependent upon having a battery in the circuit. However, if you start the engine without a battery or with a dead battery, the charging system can overpower the light bulbs and blow them out, because the battery is an electrical load for the system.

If the engine looks like it has been out/apart, perhaps the cam timing is off. Check compression readings after you adjust the valves to .002" cold on the Compression stroke, with piston at TDC (T mark). Bikes that sit for years often have a valve open, depending on how they were oriented when the engine was shut off. Moisture and corrosion can build up on the valve face/seat area, which prevents the valve from closing properly. Open valves = no compression = no start. A compression reading will reveal leaking valves/piston rings. Likewise, when engines are left with valves open, moisture can work its way into the cylinder, rusting the cylinder walls, causing ring sealing issues. Stock compression specs are 170psi from Honda.

Bill Silver