i'm restoring an Honda SOHC engine 250, i fixed the full electrical system and i can see the spark testing it near the engine. (Not sure if gap is correct of the new spark plug), there is compression and i clean the valve and had the timing set by the Honda mechanics. However even when spraying starting fuel inside there is crank but not ignition. Could this be a spark problem?
There are 3 components in the triangle of fire, namely: Oxygen, heat (in this case, the engine's spark) and the fuel. We've established that the engine has crank and there is spark, we might as well check your oxygen and fuel supply. See if your carburetor delivers the air-fuel mixture in the cylinder. Try cleaning the carburetor thoroughly. Or maybe you just have a bad spark plug?
Ultimately, your problem will be solved by using the trial and error process. Test each component to verify each component is working properly so that we can lean the components out and identify the culprit of the problem