Cummins/Onan — Carbon removal
Maintenance · Combustion chamber
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- With cylinder head removed, clean carbon from inside the cylinder head, piston tops, and around valves with a carbon scraping tool.
- Finish with a wire brush; have each piston at top of its stroke when cleaning the piston top.
- Wipe loose carbon particles from inside the cylinder with a clean cloth.
- Inspect intake and exhaust valves and their seats; report unsatisfactory condition.
- Clean the top of the cylinder block and head contact face; set cylinder-head gasket and head in position.
- Install cylinder-head nuts and cap screws with all lockwashers, taking up evenly.
- Ensure all drains closed and refill cooling system; connect spark plug wires to proper plugs.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Firing order 1-3-4-2
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.