Yamaha YP30G Owner's Manual page 30

4. Compression
Insufficient
2 Worn out piston and cylinder .... Consult dealer.
2 Loose cylinder head nuts .... Tighten nuts properly.
2 Damaged gasket .... Replace gasket.
Water does not draw up
2 Loosened priming and/or drain plugs .... Tighten.
2 Loosened hose joint and/or band .... Tighten.
2 Damaged O-ring and/or gaskets .... Replace.
2 Damaged mechanical seal .... Consult dealer.
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