cRanbrook build



Spare_Parts

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I wouldn't polish it though,it looks polished under the slide because of the cut after being cast.The rough casting surface is better for keeping the fuel atomized,a smooth surface promotes droplets to fourm.
I always wondered about polished bores on carbs because of that. Thank you.
 

dparenti13

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Sep 24, 2016
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I wouldn't polish it though,it looks polished under the slide because of the cut after being cast.The rough casting surface is better for keeping the fuel atomized,a smooth surface promotes droplets to fourm.
I know this probably has such a negligible effect, but would polishing the "velocity stack part" improve flow since the fuel is atomized in the venturi anyways?
 

CrazyDan

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Jul 9, 2016
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Any part of the system after the fuel is added should be opened to the size of the carb entry and exit into the cylinder without polishing, to the cylinder. As Street Ryderz said, the rough edges keep the fuel atomized better. Just get rid of hard edges when porting to the cylinder imo, don't make it shiny. Just as he said, make it shiny after the cylinder. When you allow the fuel to re-condense before combustion it can cause issues, especially in 2 strokes.
On another note, something I have been pondering on. A large carb only bogs on low end because the venturi effect doesn't work correctly with less air pumping by till a higher rpm. Maybe we can build up the lip a little where the main jet squirts in to increase pressure in a larger carb? A little bit of jb weld on the pinch point where the main's fuel is sucked in?
 

JerboaJohn

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optimum would be a 2 barrel carb or just 2 carbs,, but does anyone really use those dual intakes? a flapper inside connected to a lever could switch between 2 carbs
 

The_Aleman

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May 2, 2007
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That's how the GM Vortec system works, you want your intake charge to "tumble around" to aid complete combustion.
Polished intake (velocity stacks) before mixing; strategically rough, yet smooth travel after.

As far as multi-carb goes, I don't think these warrant any thinking of that. I'm no expert on bicycle engines, but I've been an automotive gearhead most of my life - built a high-12-second Bug in the 90's - and from my experience we already have more than enough flow from the single-throat carbs that are available. Foureasy agreed with that back when he made the dual-carb intake, the single carbs we have flow way more than enough CFM. A chinagirl's NT will even work on a 97cc flathead 4-stroke, because it flows enough CFM, and plenty of jets are available.

Multi-barrel, now there's a case to be had for that. If one wanted to get crazy and mess with n2o, there has to be a way to get extra fuel :LOL:
 
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