Honing And Boring - Yanmar 3TNV82A Service Manual

Crankshaft and Camshaft Components

Honing and Boring

Pistons must move freely in the cylinders while
maintaining adequate compression and oil sealing.
If the cylinder walls are scuffed, scored,
out-of-round, or tapered beyond specifications,
rebore and hone to restore cylinders to usable
condition. Slight imperfections can be corrected by
honing alone.
1. Boring - Significant cylinder damage may be
corrected by boring the cylinder to an oversize
dimension. Refer to the appropriate parts
catalog for available oversize pistons and piston
rings.
• Boring a cylinder should always be done in a
properly equipped machine shop.
• A bored cylinder should always be finished with
a hone to properly prepare the cylinder surface
so the new piston rings will seat properly.
• After the cylinder has been bored and honed,
install the appropriate oversize pistons and
piston rings.
2. Honing - Minor cylinder imperfections may be
corrected by using a rigid cylinder hone
(Figure 6-126, (1)). Be sure not to exceed the
maximum cylinder bore specification.
Deglazing - A used cylinder that did not require
boring or honing, should always be deglazed with
a ball hone (Figure 6-126, (2)) before installing
new piston rings. This will properly prepare the
cylinder surface to allow new piston rings to seat
properly.
Note: When honing a cylinder, with either a
ridged hone or a ball hone
(Figure 6-125, (1)), move the rotating
hone up and down in the cylinder bore to
accomplish a 30° to 40° crosshatch
pattern (Figure 6-125). This will provide
the ideal surface for the proper seating of
new piston rings.
TNV DI Service Manual
CAUTION
Do not allow the honing tool to operate
in one position for any length of time.
Damage to the cylinder wall will occur.
Keep the tool in constant up-and-down
motion.
Figure 6-125
• Use a 50:50 mixture of diesel fuel and engine
oil as a honing fluid.
• Use a 300-grit hone at 300 - 1200 rpm
(Figure 6-126).
(1)
Figure 6-126
IMPORTANT
Solvents will not adequately remove honing
residue, resulting in premature piston and
ring wear. Always wash cylinders using hot,
soapy water.
ENGINE
0000090en
(1)
0000248A
(2)
0000249B
6-83