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@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8616
Location: Victoria, Australia
 
Veni, Vidi, Posti
@ginch avatar
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8616
Location: Victoria, Australia
UTC quote
I just saw this from SCK and thought it looked pretty good. It's meant to flow twice as much as the SIP one, for about 3 euro more.

External inline image provided by member with no explanatory text

Interestingly it doesn't seem to have the brass pipe thingy that sticks up... mine came loose somehow at one time and it wouldn't turn off. Or possibly you just cant see it in the picture?

http://www.scooter-center.com/scoweb/pages/productdetail.grid?product=290296727561328&target=productdetail&category1=C&category2=CAT
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
 
Mr. Clean
@vader19 avatar
P,SUPER,V90, 50 Special
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UTC quote
I have two... the're great... good quality...
I have the simple ones (your first pic) not the one with the low fuel light... those are cool.

Note! They do have reserve.. I have two and didn't even know it.. I could have sworn I read it in the description.. now I don't have to sweat it... Thank Ginch!
⚠️ Last edited by Vader19 on UTC; edited 1 time
UTC

Molto Verboso
Joined: UTC
Posts: 1220
Location: NC, USA
 
Molto Verboso
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Location: NC, USA
UTC quote
I don't really expect this to be received very well.

The video is truthful in that the fast flow fills up the test container faster. Definitely. Through an open hose with no fittings or reductions.

The carb's float chamber is basically a commode tank. Fuel flows in, the float rises, and cuts off the fuel. The head pressure developed by the fuel level in the fuel tank's distance above the banjo fitting is relatively constant. A fast flow tap does NOT increase pressure.

Current flow in any fluid system is limited by the smallest orifice in the system. The smallest orifice on the way to the carb is the fuel tap body selector holes (not the barbed outlet ID). As the video shows, the fast flow definitely wins, through an open hose into a vessel. In reality, the hose does not empty into an open vessel.

At the float assembly, the flow is determined by the needle/seat. As the float falls away, the flow increases as the needle uncovers the seat. Tests I've done in the past show that flow to be less than the maximum flow an original tap can pass (SI carb). So unless you have a faster flowing float assembly than stock, then the original tap can always outflow a stock float assembly. Whether that flow rate can keep the float chamber full is a different story. Hook up the three taps in the test to identical float assemblies, then run the test in the video to see if flow increases.

In the float chamber (SI carb) there is a small hole that allows flow into the jet wells on the other side of the float chamber. Bottom, engine side. The hole size the fuel flows through is actually smaller than it appears, as it is necked down a little in the center. It is the smallest hole in the system before the jets. ALL the fuel the engine uses goes through that small hole under suction from the carb's venturi. The flow from the float assembly outpaces that under normal, original conditions. If you have built a screaming monster, fitted with an SI carb, that hole flows all you use. The enrichner uses a separate hole.

Frictional losses do come into play in fluid flow systems, but flow rates compared to lines sizes and orifice lengths make them insignificant in our case.

Rule of thumb fuel consumption for a two-stroke is about 1 gallon per hour per 10 horsepower. A little over 2 ounces per minute per 10 HP. Stock Rallys and Ps have been doing that for years. Any time I replace a tap I time open flow into a measured container. Replacing an original tap with problems that cause less than original flow with a "high flow" will solve that restriction, but is not necessary if the increased possible flow is not used or needed.

Simple analogy. The 1/2" water pipe to your shower head can flow maybe 10 gallons per minute at rated pressure, but that water saver reducer nozzle required by law (jet, needle/seat equivalent) reduces that to 2 gpm.
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
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Mr. Clean
@vader19 avatar
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UTC quote
I dig all that Bart.. thanks for the info.. really, but i use them on gas gulping 32 and 33mm flatslides... and I know I can use the fuel. I don't want to be running WO and die for lack of fuel... if you know what I mean. Unfortunately my bike probably get 25 miles per gallon... Maybe! Razz emoticon Overkill tap? maybe, but like I said.. I need the gas.
@rgconner avatar
UTC

Ossessionato
GTS250
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Ossessionato
@rgconner avatar
GTS250
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UTC quote
Heh Heh heh....

He said "orifice", Bevis.

heh heh...
@viney266 avatar
UTC

Member
stella 2t
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Location: Westminster, Md
 
Member
@viney266 avatar
stella 2t
Joined: UTC
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Location: Westminster, Md
UTC quote
for those stock and 24/24 carb issues

http://www.sip-scootershop.com/main/base/Results.aspx?t=128325t5&d=%28ape,lam,old,px,sma%29&a=1&sort=0

^^^ I think that will fix your orifice issues.
@bholinath avatar
UTC

Addicted
Rally 200, SS 180, ET3
Joined: UTC
Posts: 685
Location: UK
 
Addicted
@bholinath avatar
Rally 200, SS 180, ET3
Joined: UTC
Posts: 685
Location: UK
UTC quote
i agree, fuel flow will be restricted by the smallest hole in the system...

i've fitted this to my si carb, but i don't see what difference there is between this and the DRT modded one in previous link? (expect it being twice the price)

http://www.sip-scootershop.com/en/products/float+chamber+cover+dellorto+_12832540
or am i missing something?

and i also drilled out the supply hole in the float chamber to 2mm

in my eyes, this is a much easier way to improve fuel flow into the venturi than messing around changing the tap... and its something i feel you should do if you fit a new fast flow tap anyway!!

*edit and if you really want to mess up your jetting, try one of these horrible things... http://www.sip-scootershop.com/en/products/spacer+float+chamber+serie+pro+_92260000
@scooterist avatar
UTC

Molto Verboso
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1540
Location: Tucson, AZ
 
Molto Verboso
@scooterist avatar
71' Sprint Veloce , 05' Vespa PX150, 1978 P200E
Joined: UTC
Posts: 1540
Location: Tucson, AZ
UTC quote
This is my overview on this, I know that this newest fuel tap obviously flows more and faster than the oem but that is significant since the demand of fuel is still regulated by the amount of fuel that the engine and carburator can suck.

Basically, you can feed the carburator with a firetruck fuel line hose and you will never make any diference in performance. I can see a good application on an old carburated drafg strip car where the demand of fuel is like liters pers second but on a vespa engine you have to pass all the gas thorugh the main jet and that is a big restriction.

This upgarded fuel tap wouldn't do much in my opinion. my .2c
OP
@ginch avatar
UTC

Veni, Vidi, Posti
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8616
Location: Victoria, Australia
 
Veni, Vidi, Posti
@ginch avatar
74 Super, 75 Super, PX project, LML off-roader and '66 Blue Badge Smallframe
Joined: UTC
Posts: 8616
Location: Victoria, Australia
UTC quote
Vader19 wrote:
... only thing is, there's no reserve.. and on the lever up is off, down is on..
Well that sucks. The link I followed to find it definitely said "with reserve".
bholinath wrote:
*edit and if you really want to mess up your jetting, try one of these horrible things... http://www.sip-scootershop.com/en/products/spacer+float+chamber+serie+pro+_92260000
So, what's wrong with this thing, it kind of sounds like a good idea. Is it that it raises the level of the fuel in the jets themselves? What did it do when you tried it?
scooterist wrote:
Basically, you can feed the carburator with a firetruck fuel line hose and you will never make any diference in performance. I can see a good application on an old carburated drafg strip car where the demand of fuel is like liters pers second but on a vespa engine you have to pass all the gas thorugh the main jet and that is a big restriction.

This upgarded fuel tap wouldn't do much in my opinion. my .2c
I never said "fit this tap for great performance", I just figured if I was replacing my tap then this would be a good one for not much money... I might never see the benefit from it but who knows? But not much good to me without a reserve.
@vader19 avatar
UTC

Mr. Clean
P,SUPER,V90, 50 Special
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Posts: 10205
Location: This is't my locker!
 
Mr. Clean
@vader19 avatar
P,SUPER,V90, 50 Special
Joined: UTC
Posts: 10205
Location: This is't my locker!
UTC quote
Get the one with the electric reserve sensor / light.. my friend Mike has one.. and it works great.. mount little bulb on headset or wherever and it turns on when you're at reserve (as you'd expect)
The ones without the light have reserve setting too (thanks Ginch)
@scooterraton avatar
UTC

Ossessionato
2 - Many
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Posts: 3164
Location: Boca Raton, Florida
 
Ossessionato
@scooterraton avatar
2 - Many
Joined: UTC
Posts: 3164
Location: Boca Raton, Florida
UTC quote
Where the fast flow really worked for me was during the CBR. Hit reserve, shift to neutral, flip the lever and by the time I was ready to dump the clutch the bowl was full.

Then turn on the aux tank tap, fuel lever back to on, wait 7 minutes, aux tank off and ride with a full tank. Full fuel tank without a stop!
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