Suzuki 2000 Grand Vitara SQ625 Service Manual page 470

Cylinder Head
D Remove all carbon deposits from combustion chambers.
NOTE:
Do not use any sharp-edged tool to scrape off carbon depos-
its. Be careful not to scuff or nick metal surfaces when decar-
boning. The same applies to valves and valve seats, too.
D Check cylinder head for cracks on intake and exhaust ports, com-
bustion chambers, and head surface.
Using straightedge and thickness gauge, check flatness of gas-
keted surface at a total of 6 locations. If distortion limit, given be-
low, is exceeded, correct gasketed surface with a surface plate
and abrasive paper of about #400 (Waterproof silicon carbide
abrasive paper): Place abrasive paper on and over surface plate,
and rub gasketed surface against paper to grind off high spots.
Should this fail to reduce thickness gauge readings to within limit,
replace cylinder head.
Leakage of combustion gases from this gasketed joint is often
due to warped gasketed surface: such leakage results in reduced
power output.
Limit of distortion: 0.05 mm (0.002 in.)
D Distortion of manifold seating faces:
Check seating faces of cylinder head for manifolds, using a
straightedge and thickness gauge, in order to determine whether
these faces should be corrected or cylinder head replaced.
Limit of distortion: 0.10 mm (0.004 in.)
ENGINE MECHANICAL (J20 ENGINE) 6A4-51