Vintage Engine Repairs
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I hope it helps 
Stihl’s Official Carburettor Adjustment Procedure
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bertfixessome
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As some one who has been playing with carburettored engines for over 60 years I nearly gagges when I first read these proceedures .
To me it appears that they are trying to make it as complicated as possible to diswade home owners from touching their carbs.
I tune them the same as I would tuns anything from a 1975 Amal to a 1912 Sentspray .
I usually start with the recommended starting settings , start the device & warm it up
hen I close off the H needle completely as it should not be supplying fuel at idle
Then it is just a case of turning the L needle in till it starts to miss lean then out till it starts to miss rich and back to 1/2 way between the two .
From there the H is wound out.
If doing this causes the engine to pick up speed then the throttle stop ( why do they call this thing a LA needle ) gets wound out till opening the H has no effect .
If the throttle stop need to be would out a long way then I might check the L needle a second time .
Then the H is wound out til the engine starts to 4 stroke ( missing rich ) then back in till it starts to miss lean and finally 1/2 way between these positions with a fraction closer to too rich
After that it is an acceleration test to fine tune the L to give a smooth acceleration
No tach needed
To me it appears that they are trying to make it as complicated as possible to diswade home owners from touching their carbs.
I tune them the same as I would tuns anything from a 1975 Amal to a 1912 Sentspray .
I usually start with the recommended starting settings , start the device & warm it up
hen I close off the H needle completely as it should not be supplying fuel at idle
Then it is just a case of turning the L needle in till it starts to miss lean then out till it starts to miss rich and back to 1/2 way between the two .
From there the H is wound out.
If doing this causes the engine to pick up speed then the throttle stop ( why do they call this thing a LA needle ) gets wound out till opening the H has no effect .
If the throttle stop need to be would out a long way then I might check the L needle a second time .
Then the H is wound out til the engine starts to 4 stroke ( missing rich ) then back in till it starts to miss lean and finally 1/2 way between these positions with a fraction closer to too rich
After that it is an acceleration test to fine tune the L to give a smooth acceleration
No tach needed
LA is german for Leerlauf Anschlag meaning idle stop.
I learned that recently from Youtube.
I learned that recently from Youtube.
bertfixessome
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Interesting but it is called an LA screw on Zama , Walbro & Tilotsen carbs
All of who were making cube carbs back in the days when Stihl was fitting slide carbs
But it sounds reasonable as all of their code numbers FS, BR etc apparently code out to what the unit does in German
All of who were making cube carbs back in the days when Stihl was fitting slide carbs
But it sounds reasonable as all of their code numbers FS, BR etc apparently code out to what the unit does in German
AlexStromberg
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Not really interesting, just a german product.
