Mixer Tubes SI Carbs

[Norrie Bodge]

To weaken you'd drill a hole
To richen you'd plug holes

My malossi 210 using a T5 24/24g carb
Was rich with BE3 emulsifier straight off the throttle so I changed to a BE2
& loads better now

[rosscla]

To weaken you'd drill a hole
To richen you'd plug holes

My malossi 210 using a T5 24/24g carb
Was rich with BE3 emulsifier straight off the throttle so I changed to a BE2
& loads better now

Which is in line with chart posted above which suggests the BE2 2/4/7 is leaner lower down than the BE3 3/5/6.

It doesn't align though with the picture labeled 'larger' to 'smaller' and suggests a progression.

[bazman]

Strange
When I had issues with my 210 being rich midrange , I changed from be3 to be 4 to lean off .

[rosscla]

I'm guessing it's a mixture of the whole lot i.e. air corrector / main and pilot

'Rich straight off the throttle ' suggests at the lower range so more pilot involved?

May be if you had a bigger corrector and smaller main ..?

[Ginch]

It doesn't align though with the picture labeled 'larger' to 'smaller' and suggests a progression.

Perhaps the person who labelled the chart really didn't know either?

Just reading a little more here - http://forums.fourtitude.com/showthread ... 0c9a927b0f In the Weber tuning book it's saying there is also an effect due to the step in the tube... it says that as the diameter of the tube decreases, less vacuum from the venturi is needed to draw fuel from that section. The more I read the less grasp I have!

Another useful point from another Weber guide, though not specifically on mixers: "By putting in a smaller air corrector you will tend to richen the mixture towards the middle and top end of the rev range, and vice versa."

[rosscla]

The more I read the less grasp I have!

That's kind of where I got to, maybe I should just have taken baz's word (sorry mate), but I'd started reading by then mane I like to understand things

A little surprised none of the tuners have an opinion...

[santacama]

I use Keihin

[freakmoped]

& also take into consideration what

dellorto says

emulsion tubes act as air brakes to slow down the flow of fuel

(got it 10y ago from a friend and promised him not to share the whole document... but an extract is ok )

same in excel

(vollgas=fullthrottle)

area of the tubes holes



a topic follower - ah, mike is also here, hy ginch
asked me if i know how this works. i said:
no i dont, i have some information about it,
but basically i dont care about the details for one easy reason:

for rotary valve si touring tuning up to 25hp on the wheel you need only 2 tubes:
1) be3 is fine with new touring exhaust
2) be2 is needed with rap

dellorto kind of confirms it, i just looked at the table thinking of my ranking
1) be3 is a mixture of 1 and 2.
2) be2 is enrichment in high rpm when the exhaust comes into resonance and needs/sucks a lot
3) all the others are different and - based on know be3 works with EVERY engine 125-225ccm - therefore not needed.

rest is done with idle- & main jet as well as air corrector ( is it the right name? ^^)
it worked, it works and it will work, i tried it on dozens of engines 125-225ccm
never ever used other tubes, or even other slides

no need for it, so why bothering

dont get me wrong: respect folks if you thing about it!
its just my opinion that details are not needed
thereforefmp08 SIsetup wount include such details
but any other usefull information about the awesome si carbs

[Norrie Bodge]

Great post m8

[Ginch]

2) be2 is enrichment in high rpm when the exhaust comes into resonance and needs/sucks a lot

You are saying that BE2 is richer in high rpm than the BE3. The chart says the size of the holes in the top of the BE3 is 7.1mm2. The BE2 has much bigger holes at the top with 14.1mm2.
If you are correct then more holes at the top = richer and Vizard is wrong. Or that his theory doesn't apply to SI carbs, or we are reading it wrong.

It would be interesting to drill additional holes in a BE2 and see if it gets very rich.