Husqvarna 340 User Manual download pdf (Page 51)

50 – English

Appendix A

Repair instructions

Basic adjustment for EPA II carburetors

After replacing the carburetor or high speed and/or low

speed needle on an EPA (The US Environmental

Protection Agency) certified product a basic adjustment

must be carried out as described below in order to meet

the EPA-requirements. This to achieve as low emissions

as possible. This instruction is made for USA & Canada

only. On EPA carburetors both the H- and L-needles are

fitted with caps to prevent the chain saw operator from

changing the adjustment above EPA standard. The caps

can be removed to achieve richer or leaner adjustments.

To set the needles correctly an adjustment sleeve is fitted

from the factory over the caps to lock them in maximum

allowed settings.

When correctly set the caps must be fixed on the nee-

dles. The adjustment sleeve then can be removed. Over

the caps on complete sparepart carburetor, there is a

plastic sleeve which is intended to lock the caps at the

richest position (anticlockwise towards stop) during the

time that the needles are adjusted. When the adjustment

is complete and the caps have been fixed on the nee-

dles, the sleeve is no longer of any function and can be

removed.

NOTE! On the complete spare part carburetor, the L-

needle is adjusted from the factory.

NOTE! Before making any adjustments the following

must be done!

• Mount, for this model, approved bar & chain combina-

tion (See Technical data in the Operator’s manual).

Model

340/345/350 16”

346XP/351 16”

• The chain should not be tensioned more than that it

remains ~0,2 inches to the bar.

• Mount a new air filter.

Replacement of the H-needle or complete carburetor

1. Screw the new H-needle to the bottom and turn it

counterclockwise ”A” turns.

Model

340/345/350 A = 3/4

346XP/351 A = 3/4

2. Check that:

The H-cap is adjusted to its richest setting. (Turned

counterclockwise to stop). The cap is not fixed to the

needle, it should rotate independently. Adjust the L-cap

to a center position (1/4 turn counterclockwise =

minimum, 1/4 turn clockwise = maximum).

3. Start the engine. If necessary, adjust the idling speed

with the T-screw until the chain stops.

4. Adjust the H-needle to give a top speed of ”B” rpm.

Model

340/345/350/351 B = 12 000

346XP B = 13 000

Use a narrow blade screwdriver (Ref.no. 531 00 48-63)

and insert it through the hole in the cap (max. blade width

2 mm/0.08 inch).

5. Let the engine run at ”B” rpm ~ 1 minute, until warm.

6. Adjust the H-needle to a top speed of ”C” rpm.

Model

340/345/350/351 C = 13 700

346XP C = 14 300

7. Check that the H-cap is still adjusted to its richest

setting. (Turned counterclockwise to stop). NOTE!

The H-needle must not rotate!

8. Gently knock the H-cap into position. Use a 5 mm/0.2

inch mandrel (for ex. the locking pin for the bevel gear

ref.no. 502 02 61-03). This is a basic carburetor

adjustment. Further fine adjustments, within the limits

the caps allow, may be necessary to achieve optimum

performance. See the Operator’s manual.

Replacement of the L-needle

1. Take off the cap from the L-needle using e.g. a pair of

cutting pliers and unscrew the needle.

2. Screw the new L-needle to the bottom and then turn it

counterclockwise ”D” turns.

Model

340/345/350 D = 1 1/2

346XP/351 D = 1 1/2

3. Press a new L-cap on the L-needle to the first stop,

which means that the cap is not fixed to the needle, it

should rotate independently.

4. Adjust the L-cap to the richest position (turned

counterclockwise to stop) without turning the needle.

5. Let the engine run at ~ ”E” app.1 minute until warm

and then let it run on idle.

Model

340/345/350/351 E = 12 000

346XP E = 13 000

6. Adjust the idle speed to ”F” rpm.

Model

340/345/350 F = 2 700

346XP/351 F = 2 700

7. Adjust the L- needle until the highest possible idling

speed is achieved and then turn the

L-needle 1/2 turn counterclockwise. Use a narrow

blade screwdriver w. ref.no. 531 00 48-63 and insert

through the hole in the cap (max. blade width 2 mm/

0.08 inch) .

NOTE! If the chain rotates, turn the idling speed

screw (T) counterclockwise until the chain stops.

8. Check that the L-cap is still adjusted to its richest

position. (Turned counterclockwise to stop).

NOTE! The L-needle must not rotate!

9. Gently knock the L-cap into position. Use a 5 mm/0.2

inch mandrel (for ex. the locking pin for the bevel gear

ref.no. 502 02 61-03).

This is a basic carburetor adjustment. Further fine

adjustments, within the limits the caps allow, may be

necessary to achieve optimum performance. See the

Operator’s manual.

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Husqvarna 340 User Manual Page 51

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