4
B0400066
SERVICE
Replacement of the H-needle or complete carburettor
1. Screw the new H-needle gently clockwise to closed position and then turn it counterclockwise
”A” turns.
Model Model
136/141 A = 2 359 A = 3/4
55 A = 1 1/4 395 XP A = 3/4
340/345/350/353 A = 3/4 3120 XP A = (non adjustable fixed jet)
346 XP A = 3/4 336/339 XP A = 1 1/2
357 XP A = 3/4 334 T/338 XPT A = 1 1/2
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. Use a tachometer.
Model Model
136/141 B = 12 000 359 B = 12 500
55 B = 12 000 395 XP B = 13 000
340/345/350/353 B = 12 000 3120 XP B = (non adjustable fixed jet)
346 XP B = 13 000 336/339 XP B = 12 500
357 XP B = 13 500 334 T/338 XPT B = 12 500
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 Model
136/141 C = 13 500 359 C = 13 100
55 C = 12 500 395 XP C = 12 500
340/345/350/353 C = 12 700 3120 XP C = (non adjustable fixed jet)
346 XP C = 14 300 336/339 XP C = 13 100
357 XP C = 14 000 334 T/338 XPT C = 12 900
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 carburettor adjustment. Further fine
adjustments, within the limits the caps allow, may be necessary to achieve optimum
performance. See the Operator’s manual.
English 3 (4)
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