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Author Topic: Idle and high speed adjust  (Read 3045 times)


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Idle and high speed adjust
« on: March 10, 2007, 04:21:43 PM »
5 hp Craftsman snowblower, tecumseh engine # 143-696082. What are the settings for the idle and highspeed? idle screw on side of carb. and highspeed on bottom of fuel bowl?  Thanks,  Jerry


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Re: Idle and high speed adjust
« Reply #1 on: March 13, 2007, 05:25:07 AM »
As either mixture screw lets gas get into the carb, some intereaction between the two, but idle is set at idle and high speed at open throttle, generally both for maximum rpm and smooth running.  Too lean, you get misfire, too rich, surging and smoke from the exhaust. If you have a phototach, can go back and forth and adjust for maximum rpm on each range, a couple of times gets it pretty close, but your ear can serve just as well if you listen to the pitch.

Set it a little on the lean side, your engine runs hotter and won't last as long, on the rich side, carbons up the spark plug first, but runs cooler, either is bad, also, too lean and the sucker won't start.  In general, a PITA.

Offline alexandjojo

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Re: Idle and high speed adjust
« Reply #2 on: April 26, 2007, 08:52:43 AM »
start by setting the low speed adjustment on the side of Card by turning the screw in fully until it stops and turning or backing it out 1 full turn.  Like-wise with the high speed adjustment-but turning it out about 1 1/2 trun of the screw.  With a fully clean carb this adjustment will get you very close.  The basic adjustment upon running that I have found needing adjustments is usually the high speed upon start up on high throttle and the idle speed.   As nickd says about the rich and lean content he is right.  You will have to hear and determine how much to turn in or backout on the low or hi side.


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