i have a falcon 110 it will run fine for about 15 minutes. then wont start and no spark at the plug.

coil or cdi

 

I would try a new spark plug then a new Lead wire (the one that goes to the spark plug)
Check all grounds and battery connections.

Problem: Engine will not start or is hard to start (No spark)
Condition Remedy
1. Spark plug fouled 1. Clean - replace plug
2. Spark plug wet 2. Clean - dry plug
3. Magneto defective 3. Replace magneto
4. CDI unit defective 4. Replace CDI unit
5. Ignition coil defective 5. Replace ignition coil
6. High-tension lead open - shorted 6. Replace high tension lead

Engine stalls easily
Condition Remedy
1. Spark plug fouled 1. Clean plug
2. Magneto defective 2. Replace magneto
3. CDI unit defective 3. Replace CDI unit
4. Carburetor jets obstructed 4. Clean jets
5. Valve clearance out of adjustment 5. Adjust clearance

Problem: Idling or low speed impaired
Condition Remedy
1. Slow jet obstructed - loose 1. Clean - tighten jet
2. Slow jet outlet obstructed 2. Clean outlet
3. Low speed fuel screw setting incorrect 3. Adjust screw
4. Starter valve not fully closed 4. Adjust valve
5. Float height incorrect 5. Adjust float height

Problem: Spark absent or weak
Condition Remedy
1. Ignition coil defective 1. Replace ignition coil
2. Spark plug defective 2. Replace plug
3. Magneto defective 3. Replace magneto
4. CDI unit defective 4. Replace CDI unit
5. Pick-up coil defective 5. Replace pick-up coil