Quote:
Originally Posted by two-fiddy
sparks are big, clear, and strong
carb diaphragms are both soft and supple
your third point is intimidating as i have not yet and i hoped to avoid cracking the engine
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The thing is that sparks can jump big at atmospheric pressure, but not under compression.
If you can, observe if both needles go up together and inmediately as you twist the handle.
Diaphragm could be leaking and would only rise the needle when vacuum gets strong.
It could also have abnormal resistance in its guides or be incorrectly linked to the needle.
For the valves, you don't have to split the engine.
The valves require periodic adjustment of the specified gaps.
A leak down test could tell you if all the valves are closing properly.
A compression test would tell you about the condition of the rings.