Honda Small Engine Spark Plug Torque
Spark plug torque, plug part number, and gap for Honda small engines — the GCV walk-behind mower engines, the GX commercial horizontal-shaft range, the GC pressure washer platform, and the EU series inverter generators.
Spark plug torque by engine
GCV160 and GCV190 (160-190cc OHC, the older platform found on most residential mowers): 14 ft-lbs (20 N·m) for the 14x1.25 plug, per Honda shop manual 61ZM000 — Honda's owner's manual gives an equivalent alternative method instead: thread the plug in by hand to seat the washer, then turn an additional 1/2 turn for a new plug (1/8-1/4 turn if reusing one); NGK BPR6ES on pressure-washer applications, BPR5ES otherwise, gap 0.028-0.031". GCV170 and GCV200 (166-201cc OHC, the redesigned platform): 15 ft-lbs (20 N·m) — the one GCV generation Honda does give a numeric spark-plug torque for. GX120, GX160 and GX200 (118-196cc OHV commercial): 13 ft-lbs (18 N·m), NGK BPR6ES or DENSO W20EPR-U — Honda shop manual 61Z4H00 prints 18 N·m (1.8 kgf·m, 13 lbf-ft) for the M14x1.25 plug in its TORQUE VALUES table and again in the plug replacement procedure. GX240, GX270, GX340 and GX390 (242-389cc OHV): Honda publishes no numeric plug torque for these. The GX240-390 UT2 shop manual has no spark-plug row in its torque table and its maintenance section says to seat a new plug finger-tight and then turn it 1/2 turn (1/8-1/4 turn if reusing one). The iGX240/iGX340 table in the same manual does print 18 N·m (13 ft-lbs) for the same M14x1.25 plug, so 13 ft-lbs is a reasonable target with a wrench, but do not assume the small-GX figure carries over to this larger head. The figures of 18-22 and 22-26 ft-lbs once shown here were the cylinder head bolt torques (24 N·m on GX120/160/200, 35 N·m on GX240-390) misapplied to the spark plug; at nearly double the real figure they strip the aluminium head. GC160 and GC190 horizontal shaft (pressure washer platform): 14 ft-lbs (20 N·m), NGK BPR6ES — shop manual 61ZL800 prints 20 N·m for the M14x1.25 plug, the same spec as GCV170/GCV200 above, which Honda rounds to 15 lbf-ft in its own manual. Not a GX carry-over. GX, GC, and GCV160/190 gap to 0.028-0.031".
The EU inverter generators are different
The Honda EU2000i and EU2200i take an NGK CR5HSB on a small M10x1.0 thread at just 9 ft-lbs (12 N·m), with a 0.024-0.028" gap — a different plug and a much lower torque than the rest of the range. Do not substitute a BPR6ES because it is what you have on the shelf, and do not carry a GX figure over. Both mistakes are common and both damage the head. The larger EU3000iS and EU7000is use GX-family engines and take the GX-frame plug instead.
Getting spark plug torque right
Spark plugs thread into aluminium heads, so over-torquing strips the head rather than the plug and turns a two-dollar part into a cylinder head repair. Torque cold, never hot — aluminium expands and a plug torqued into a hot head will be loose when it cools. If you cannot fit a torque wrench, seat the plug finger-tight against the washer and then turn it half a turn for a new gasket plug.
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