Big Bore Carb = More Power! FREE MOD!

ExtremeModz · 06-16-2008, 08:38 PM

This is a really neat mod I just thought up. I was looking at my stock carb when I realized there was a pretty big blockage in both the engine side of the stock carb and the intake pipe. There is about 1 mm or so of metal that hangs over the tunnel of each. I decided to take out my dremel and get to work. This is what I came up with. After I was done I had to richen up the mixture and retune the carb a bit but the low end I got was just amazing!

kczukiman · 06-16-2008, 08:43 PM

Thanks for sharing and welcome to the forum.

Rizn · 06-16-2008, 09:01 PM

Yeah but what about the gasket, how does it seal without it

ExtremeModz · 06-16-2008, 09:12 PM

Quote:

Originally Posted by Rizn

Yeah but what about the gasket, how does it seal without it

I took the gasket out so I would not damage it when I was working on it.

Sorta like this... 8)

dieselhead · 06-16-2008, 11:41 PM

Interesting post. When I saw all the grind marks in the throught of your carb, it reminded me of a buddy of mine telling me the intake porting should have a slightly rough to the touch surface. He claimed it was proven to create more turbulance in the air which in turn helped atomiz the air/fuel mix. Thats going back to the mid 70's! Looks like you nailed it on that point!

ExtremeModz · 06-17-2008, 10:45 AM

Your buddy is a smart guy. That's what I was going for, I could have easily polished it off but I decided to leave it with that slightly textured feel for better atomization. Found a porting writeup on Wikipedia. Looks like even in 2008 he is still correct.

"A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means."

mebigdave · 06-17-2008, 03:51 PM

I found this website when I was doing my home work before getting my new 30mm Walbro double pump carb for the Shineray.

http://www3.telus.net/dougsimpson/CVcarb.html

06-16-2008, 08:38 PM	#1
ExtremeModz Join Date: Jun 2008 Posts: 27	Big Bore Carb = More Power! FREE MOD! This is a really neat mod I just thought up. I was looking at my stock carb when I realized there was a pretty big blockage in both the engine side of the stock carb and the intake pipe. There is about 1 mm or so of metal that hangs over the tunnel of each. I decided to take out my dremel and get to work. This is what I came up with. After I was done I had to richen up the mixture and retune the carb a bit but the low end I got was just amazing!
	0

06-16-2008, 08:43 PM	#2
kczukiman Join Date: Jul 2007 Location: Independence,Missouri Posts: 1,049	Thanks for sharing and welcome to the forum. __________________ Kman 2007 HI-BIRD 250 2007 Vbike V4S 250
	0

06-16-2008, 09:01 PM	#3
Rizn Join Date: Apr 2008 Posts: 127	Yeah but what about the gasket, how does it seal without it
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06-16-2008, 11:41 PM	#5
dieselhead Join Date: Jan 2008 Location: Catskill Mnts NY Posts: 85	Interesting post. When I saw all the grind marks in the throught of your carb, it reminded me of a buddy of mine telling me the intake porting should have a slightly rough to the touch surface. He claimed it was proven to create more turbulance in the air which in turn helped atomiz the air/fuel mix. Thats going back to the mid 70's! Looks like you nailed it on that point!
	0

06-17-2008, 10:45 AM	#6
ExtremeModz Join Date: Jun 2008 Posts: 27	Your buddy is a smart guy. That's what I was going for, I could have easily polished it off but I decided to leave it with that slightly textured feel for better atomization. Found a porting writeup on Wikipedia. Looks like even in 2008 he is still correct. "A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means."
	0

06-17-2008, 03:51 PM	#7
mebigdave Join Date: Dec 2007 Location: New Zealand Posts: 196	I found this website when I was doing my home work before getting my new 30mm Walbro double pump carb for the Shineray. http://www3.telus.net/dougsimpson/CVcarb.html
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