buell s1 lightning '97 Manual

 

Because of their complex shape, the pistons cannot be accu-
rately measured with standard measuring instruments.

The pistons have the typical elliptical shape when viewed
from the top. However, they also are barrel-shaped when
viewed from the side. This barrel shape is not symmetrical.

Any damage to the piston will change its shape, which will
lead to problems.

 

Since pistons cannot be accurately measured with standard
measuring instruments, the bore sizes must be observed.
Bore sizes are listed in 

 Example: A 0.005 in.

(0.13 mm) oversize piston will have the proper clearance with
a bore size of 3.502 in. 

 

±

 

 0.0002 in. (88.95 mm 

 

±

 

 0.005 mm)

for the 1200cc engine.

 

1.

The cylinder must be bored with gaskets and torque
plates attached. Bore the cylinder to 0.003 in. (0.08 mm)
under the desired finished size.

2.

Hone the cylinder to its finished size using a 280 grit rigid
hone followed by a 240 grit flexible ball hone. Honing
must be done with the torque plates attached. All honing
must be done from the bottom (crankcase) end of the cyl-
inder. Work for a 60

 

°

 

 crosshatch pattern.

When cylinder requires oversize reboring to beyond 0.30 in.
(0.76 mm), the oversize limit has been exceeded and cylinder
must be replaced.

 

NOTE

The same piston may be used if cylinder bore was not
changed, unless it is scuffed or grooved. However, replace
rings and hone the cylinder walls with a No. 240 grit flexible
hone to facilitate ring seating.

 

NOTE

Ring sets and pistons, 0.040 in. (1.02 mm) oversize, are not
available on 1200cc engines.

 

See 

 Piston rings are of two types: compression

and oil control. The two compression rings are positioned in
the two upper piston ring grooves. The dot on the second
compression ring must face upward. Ring sets are available
to fit standard and oversize pistons.

Piston ring sets must be properly fitted to piston and cylinder:

1.

See 

 Place piston in cylinder about 1/2 in.

(12.7 mm) from top. Set ring to be checked squarely
against piston as shown. Check end gap with thickness
gauge. See 

 for tolerance.

 

NOTE

 for end gap dimensions. Do not

file rings to obtain proper gap.

 

2.

See 

 Apply engine oil to piston grooves. Use

into their respective grooves. Be extremely careful not to
over expand, twist rings, or damage piston surface when
installing rings.

 

NOTE

Install second compression ring with dot towards top.

 

3.

See 

 Install rings so end gaps of adjacent

rings are a minimum of 90

 

°

 

 apart. Ring gaps are not to

be within 10

 

°

 

 of the thrust face centerline.

4.

See 

 Check for proper side clearance with

thickness gauge, as shown. See 

 for

tolerance.

 

NOTE

If the ring grooves are clean and the side play is still not cor-
rect, replace the rings, the piston or both.

 

Standard bore*

3.4978 in.

88.844 mm

0.005 in. OS bore
(0.13 mm)

3.502 in.

88.95 mm

0.010 in. OS bore
(0.25 mm)

3.507 in.

89.08 mm

0.020 in. OS bore
(0.51 mm)

3.517 in.

89.33 mm

0.030 in. OS bore
(0.76 mm)

3.527 in.

89.59 mm

*All bore sizes + 0.0002 in. (0.005 mm)

2747a