Author Topic: Carb Adjustment Screws  (Read 130 times)

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Offline rayvil01

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Carb Adjustment Screws
« on: February 06, 2014, 07:51:21 pm »
I'm going to ask a stupid question.  Just want to get that warning up front.  I've read a good many threads about EPA caps and adjustment limiters.  Some people advocate putting the limiters back on, or putting new ones on.  The caps will supposedly help keep the screws from walking off of adjustment.  Others say don't bother.  It seems, just from my own limited data, and what I read that it's a matter of personal preference.  There's not a peer-reviewed paper floating around on the subject.  It does seem, on a superficial level, that if a limiter cap will allow 3/4 turn, then if a screw walks 3/4 turn that's more than enough to get it off of optimum tune.  So, I tend to be skeptical that the caps do any good in terms of maintaining optimum tune.

The question I have goes back to my younger days when I ran outboard marine motors 1000+ a year crabbing on the Chesapeake.  Those motors had springs between the adjustment screws and the carb.  It was a rare, rare thing to have to adjust the carb on one of those engines.  And these were the days of breaker points.  I set a lot of points with a matchbook cover.  They would fail and slip.  But, not the carb screws.  I know that outboards and chainsaws are different species.  Still, I wonder why they don't use springs on chainsaw screws.  Can anyone shed some light on that?

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Offline KilliansRedLeo

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Re: Carb Adjustment Screws
« Reply #1 on: February 06, 2014, 08:52:17 pm »
Back in the day all the carbs had springs under the adjustment screws. However as the limiter cap technology matured under increased EPA pressure, other schemes to limit the adjust ability of the carburetors became dependent on the limiter being in place in order to keep the saw from walking off tune because of vibration.

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