Stihl 5910 890 1700 Technical Information

STIHL Incorporated
Technical Information

New STIHL Engine Repair Tool Kit part number 5910 890 1700

The new STIHL Engine Repair Kit includes tools to
inspect and clean the cylinder components of all 2­stroke and 4-stroke cycle engines.

Components included in tool kit:

The main components of the kit include
various abrasive pads for cleaning gasket
surfaces, combustion chambers, valve seats,
and exhaust ports. A cylinder leak-down tester
is also included for checking exhaust and
intake valve sealing on all 4-stroke cycle
engines and also can be used to check piston
ring sealing and piston damage on all 2-stroke
cycle engines. Other useful tools are included
that are further explained in this bulletin. All of

the tools included in the kit are also available
separately (see summary on page 9).

When performing a cylinder leak down test
the flywheel must be blocked at TDC (top
dead center) to avoid rotation of the
crankshaft as high pressure air is introduced
into the cylinder. When using on 4-stroke
cycle engines, the piston should be at TDC
on the compression stroke with both valves
closed.

To use the cylinder leak down tester on
STIHL 4-Stroke engines, remove the valve
cover and index the crankshaft as pictured
below. Verify that the piston is at TDC on the
compression stroke and both intake and
exhaust valves are closed.

BR 500, BR 550, BR 600

STIHL Incorporated
Bulletin #DLR 2007-02

August 2, 2007

DLR 2007-02 New Special Tools ea 2012.doc Page 1 of 9

STIHL 4- Stroke Engine on Shafted
Products

Index arrow between flywheel fins with lower
ignition module mounting screw.

STIHL 4- Stroke Engine on Shafted
Products

Slide blocking tool down onto clutch housing.

Examples of the flywheel blocking tool used
with STIHL 4-MIX® engines:

STIHL 4-Stroke Engine on Shafted
Products

Insert the long pegs of the blocking tool down
between the flywheel fins.

BR 500, BR 550, BR 600

Insert the locating pin of the flywheel
blocking tool into the bolt hole referenced by
the top arrow and secure the tool to the boss
at the lower arrow with a 5 mm bolt normally
used to mount the starter assembly.

DLR 2007-02 New Special Tools ea 2012.doc Page 2 of 9

should now read zero. If not, adjust the
regulator until the right gauge is set to zero.
The gauge assembly is now ready to be
connected to the spark plug adapter hose.

BR 500, BR 550, BR 600

Flywheel blocking tool installed.
The cylinder leak down tester is capable of

verifying cylinder leakage in all 2-stroke and 4­stroke cycle engines. The hose on the tester
has a 14 mm diameter thread for conventional
spark plugs and and an adapter is included for
use in engines that utilize a 10 mm diameter
spark plug thread.

Cylinder Leak Down Tester Installation

To install the tester, thread the adapter hose
into the spark plug opening. Before connecting
the gauge assembly to the adapter hose, turn
the pressure regulator knob counterclockwise
until there is no tension on the regulator knob
(damage to pressure gauge can occur if the
regulator is not backed off before connecting
to air compressor).
Connect an air source of 90 PSI minimum to
the air inlet on the pressure regulator. Turn the
regulator clockwise until the needle on the left
gauge reaches the red set point at the 12
o’clock position, the needle on the right gauge

Above view of the tester showing cylinder
leakage of 75%.

The recommended leakage should not
exceed 10%. If so, the component at fault
will need to be determined (exhaust valve,
intake valve, piston rings, scored piston).
This can be determined by listening for any
escaping air at the intake port, exhaust port
or pushrod openings in cylinder head.

If the exhaust valve is leaking, STIHL
recommends using STIHL Engine De­Carbonizer fluid (part no. 0781 313 8019)
before disassembling the engine.

DLR 2007-02 New Special Tools ea 2012.doc Page 3 of 9