how to set jets on small engine carb.


Old 10-28-01, 02:57 AM
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hi was wondering if someone could give me a rough idea on how to set the needle jets on a small engine. i have a older model ariens snow blower which i haven't used for a few years. i've changed the plug and oil and fresh gas, it starts fine but runs alittle rough, can't remember how to set the needle jets. would appreciate any help i can get thank you. red
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Old 10-28-01, 06:53 AM
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Hello redly2

Basic beginning settings should be about 1 1/2 turns out for the {L} low speed jet and about 2 turns out for the high speed jet.

Once you get the engine started, rotate the {L} low speed jet until the engine {while idling} just begins to stall out from lack of fuel, then turn out the jet until it runs slightly rich. Half way between the two turns is about correct.

About 1/8th turn open for low speed jet beyond the actual 1/2 way point should be correct. Too lean and the engine will stumble when accelerating between idle speed to full speed.

High speed setting should be done exactly the same, except turn the jet screw outwards until the engine runs too rich and then turn the screw inwards until the engine does not exhaust black unburned gas out of the muffler.

If the carb is functioning correctly, the settings discribed above will work correctly. The most common problem made is running an engine too lean in the high speed setting.

Running too lean can cause several problems for an air cooled engine. Running HOT is just one of the major problems and the other is a hole in the piston crown or dome... neither of which is desirable....

Regards and Good Luck,
Small Engine Forum Moderator
"Accurate Power Equipment Company"
Small Engine Diagnostic Service and Repair Technician.

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