Sounds like you could have a lot of carbon buildup with that much compression. I do not think those motors have but 90-100Lbs compression. I would look for fuel dripping in the carbs of the motor. Have seen a enrichment solenoid turned wrong or just leaking fuel by on the diaphragm. Could have got a piece of line inside while changing those old fuel lines. Many things could be wrong. Start by checking each cylinder for firing. Then check each cylinder for hitting while running pulling one sparkplug wire at a time. If you find a cylinder not firing suspect coil, not hitting suspect flooding from carb or solenoid.
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