No compression valve

[Fishugo]

How would I start older .028 wood boss that has no pressure relief valve?
In past I just removed spark plug, yanked a bit, then replaced it. No help this time.
Overcoming press could wreck the pull start and seems risky.

 

[dougand3]

If harder to pull than previously....probably carbon on piston top and "head" (inside of jug top). You could try a tsp of fuel on the piston top to give it lube and then pull. Disassembly and clean carbon out is more permanent. If a flat spot exists on jug...could drill / tap a 10mm x 1.0 decomp valve.