aaares
ArboristSite Lurker
Hi guys,
I have something for you specialists and tuners here.
On my older Husky 372 XP I did some mild porting and later some muffler modding.
What is REALLY ODD - it seems that I had to gradually LEAN the carb as my porting and muff. modding continued. (I made my second muffler outlet bigger gradually - in two parts). Now I have H-screw on the carb turned 0,7 turn out from fully closed position. Saw is turning 14.000 and still slightly four-stroking. I run 95-octan fuel (European number) in ratio 50:1 with "MOTUL 800 2T (Off Road)" oil. My muffler is "Jungle" type = small tube on right upper side and it's baffled inside - if it does matter. I didn't gutted it out - the baffle inside has some approximately 23 mm hole (0,9" ??) in the right bottom corner - I didn't change it. I just made some 14,3 x 20,3 mm hole in the front bracket. The ported jug is OEM Mahle 70,2cc (50 mm diameter) and it is just really slightly ported -widened exhaust to 64% of the bore diameter (chord measured), I didn't even widen the intake-just changed it's shape of "tubing". I polished the lower transfers. Didn't mess with upper transfers. There isn't any gasket under the jug - squish is still around 0,03", compression around 150 PSI.
I measured (degreed) ports (I left them OEM) - so numbers are (durations in degrees):
Exhaust: 158°
Transfers: 120°
Intake: 150°
So guys, what's up with the carb tunning ?? Why only 0,7 turns out on the H-screw? Please don't tell me that I messed something in big picture
Thanks aaares
I have something for you specialists and tuners here.
On my older Husky 372 XP I did some mild porting and later some muffler modding.
What is REALLY ODD - it seems that I had to gradually LEAN the carb as my porting and muff. modding continued. (I made my second muffler outlet bigger gradually - in two parts). Now I have H-screw on the carb turned 0,7 turn out from fully closed position. Saw is turning 14.000 and still slightly four-stroking. I run 95-octan fuel (European number) in ratio 50:1 with "MOTUL 800 2T (Off Road)" oil. My muffler is "Jungle" type = small tube on right upper side and it's baffled inside - if it does matter. I didn't gutted it out - the baffle inside has some approximately 23 mm hole (0,9" ??) in the right bottom corner - I didn't change it. I just made some 14,3 x 20,3 mm hole in the front bracket. The ported jug is OEM Mahle 70,2cc (50 mm diameter) and it is just really slightly ported -widened exhaust to 64% of the bore diameter (chord measured), I didn't even widen the intake-just changed it's shape of "tubing". I polished the lower transfers. Didn't mess with upper transfers. There isn't any gasket under the jug - squish is still around 0,03", compression around 150 PSI.
I measured (degreed) ports (I left them OEM) - so numbers are (durations in degrees):
Exhaust: 158°
Transfers: 120°
Intake: 150°
So guys, what's up with the carb tunning ?? Why only 0,7 turns out on the H-screw? Please don't tell me that I messed something in big picture
Thanks aaares
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