Maintenance; Mikuni Jet Needle; Overview - Polaris 2007 Two Stroke Service Manual

Maintenance

The impulse operated diaphragm fuel pump does not require any
specific scheduled maintenance. However, the following
procedures should be observed:
• Operation
The pump may be checked for operation by removing the fuel
supply line from the carburetor and placing it into a container.
With the engine idling at approximately 2000 RPM, a steady
flow of fuel should be visible.
• Cleaning
The pump and impulse line must be disassembled and cleaned
of foreign material in the event of piston or other internal engine
part failures which produce fragments.
• Inspection
Disconnect impulse line from pump. Connect a Mity Vac to
impulse fitting (or line) and apply 4-6 PSI pressure. Diaphragm
should hold pressure indefinitely.
The diaphragms and check valves must be carefully examined
for cracks, holes, or other damage. If in doubt as to the condition
of any internal parts, replace all diaphragms, check valves, and
gaskets.

MIKUNI JET NEEDLE

Overview

This needle (example) is a 9DH01-57. The first number is the
approximate overall length in 10mm increments of the jet
needle. The 9 indicates the needle is approximately 90mm but
less that 100mm in length.
The letters on the jet needle indicate the angle of both tapers. The
first letter designates the taper angle of the top section (closest
to the grooves) and the second letter designates the angle of the
bottom taper. The taper angles are graduated in 15' (15 minute)
increments. The jet needle marked 9DH01-57 would have a top
taper of 1_0' and a bottom taper of 2_0'.
The number following the letters on the jet needle is the serial
number and it varies with individual jet needles.
The last number, 57 indicates that the outside diameter is
2.57mm. The smaller the O.D., the richer the mixture.
FUEL DELIVERY
9DH01-57
DESIGNATOR DESCRIPTION
9 Overall length in 10mm increments
D Taper of the top section of the needle
taper of the bottom section of the
H
needle
01 Serial number
Outside diameter (O.D.) of the straight
-57
portion
4
4.5