TOPIC:

larrycavan wrote:

dutchz wrote:

I found some older pictures with different light, maybe that helps.

Sander,

It this photo, looking at what appears to be a ground in recess on the right running from the main a/c jet boss to the enrichener air circuit boss on the right.

In other pics that recess looks like it forms a sharp ridge at the bottom right section of the carb bore.

All I'm saying is if there is a sharp ridge there, it could cause turbulent flow along the floor of the carb bore. That, IMO would not be desirable.

Turbulence in the needle jet area would disrupt the pressure differential that causes the fuel to rise in the needle jet.

If the pressure differential fluctuated, then fuel flow would fluctuate as well.

Is that happening? I don't know...just appears to be possible from my experience flow testing

Wow! Talk about some whak. What's the differential pressure of 28mm carbs with turbulaticfuelization Let it floooo. Let it flooo. Vario Differencio

Dutch, by no means am I dissing what you're designing around for I freaking love it, seriously.....

? For you and Larry, have seen these where if on the outside of the manufacturer stack, shouldn't effect the flow... I think anyways....

NOTE: I'm not for the screen only type for wouldn't protect against dust... Bugs, yup but not fine particles. Now the screens on the right maybe...

Lar.... Going this route over a pod, what kind of flow differences/jet changes would be required?

And yes, I realize not all builds are the same mi amigo but due to stack design equates to increase air flow right so would run leaner but to what extent... A jet size change, clip position, richer needle etc...

Cool and interesting... Oops, just realized somewhat hijacking your post Dutch... Sorry about that....

Thoughts?

There's not a thing wrong with Sander's stacks. They're beautiful.

Keihin just refined the setup to streamline the carb bellmouth area.

With the CRS design, the air correction jet is also isolated from the main flow stream.

The 2 carburetors use a different type of needle jet arrangement that is similar in function but different in design.

nads.com wrote:

larrycavan wrote:

dutchz wrote:

I found some older pictures with different light, maybe that helps.

Sander,

It this photo, looking at what appears to be a ground in recess on the right running from the main a/c jet boss to the enrichener air circuit boss on the right.

In other pics that recess looks like it forms a sharp ridge at the bottom right section of the carb bore.

All I'm saying is if there is a sharp ridge there, it could cause turbulent flow along the floor of the carb bore. That, IMO would not be desirable.

Turbulence in the needle jet area would disrupt the pressure differential that causes the fuel to rise in the needle jet.

If the pressure differential fluctuated, then fuel flow would fluctuate as well.

Is that happening? I don't know...just appears to be possible from my experience flow testing

Wow! Talk about some whak. What's the differential pressure of 28mm carbs with turbulaticfuelization Let it floooo. Let it flooo. Vario Differencio

Uhhhhhh.... roughly 347.2 m/z @2000 jillifeet per second peak velocity with a barometric pressure of 31.7854312 with a mean manifold temperatue of 15C..... but only on a sunny day, in April

Old Man Rock wrote:

Dutch, by no means am I dissing what you're designing around for I freaking love it, seriously.....

? For you and Larry, have seen these where if on the outside of the manufacturer stack, shouldn't effect the flow... I think anyways....

NOTE: I'm not for the screen only type for wouldn't protect against dust... Bugs, yup but not fine particles. Now the screens on the right maybe...

Lar.... Going this route over a pod, what kind of flow differences/jet changes would be required?

And yes, I realize not all builds are the same mi amigo but due to stack design equates to increase air flow right so would run leaner but to what extent... A jet size change, clip position, richer needle etc...

Cool and interesting... Oops, just realized somewhat hijacking your post Dutch... Sorry about that....

Thoughts?

No worries Dave, You are right on topic. From what I understand the screen only material is fine for keeping birds and rocks from getting sucked into the motor, but as soon as you throw a filter in the mix they kill flow right quick. Look at the difference in surface area between a regular K&N filter and the opening of the stack.

As far as the jetting goes I am still working on getting it right. If I do get the chance to dyno the bike I can run back to back with standard pods and this set up.

larrycavan wrote:

There's not a thing wrong with Sander's stacks. They're beautiful.

Keihin just refined the setup to streamline the carb bellmouth area.

With the CRS design, the air correction jet is also isolated from the main flow stream.

The 2 carburetors use a different type of needle jet arrangement that is similar in function but different in design.

The stacks were made to help this older, fairly simple carb design out. It should be possible to make a similar arrangement for the keihins but if you want to add intake runner length with those carbs you could also get the longer mounting spigots. Another issue with this design for the CR's would be frame clearance, even when mounted on the standard spigots there's not enough room for a stack/filter combo.

I have not dug up the CR31's yet but was thinking about the needle jet metering. The needle jet discharge nozzle would have to be in the air stream to function, no?

[/quote]

Is that an oil catch can? thats a sweet execution:)
Are you running a magneto batteryless bike?

Thanks, yes that is a puke tank. I have a small battery underneath the tail section.

dutchz wrote:

larrycavan wrote:

There's not a thing wrong with Sander's stacks. They're beautiful.

Keihin just refined the setup to streamline the carb bellmouth area.

With the CRS design, the air correction jet is also isolated from the main flow stream.

The 2 carburetors use a different type of needle jet arrangement that is similar in function but different in design.

The stacks were made to help this older, fairly simple carb design out. It should be possible to make a similar arrangement for the keihins but if you want to add intake runner length with those carbs you could also get the longer mounting spigots. Another issue with this design for the CR's would be frame clearance, even when mounted on the standard spigots there's not enough room for a stack/filter combo.

I have not dug up the CR31's yet but was thinking about the needle jet metering. The needle jet discharge nozzle would have to be in the air stream to function, no?

The air correction jet is what is isolated from the main flow stream. Not the needle jet.

To my way of thinking, that's better because being out of the main flow stream it's more of a constant atmospheric pressure feeding that air circuit.

Where as with the a/c jet being trapped within the confines of the velocity stack, the pressure would be more subjected to variations of pressure because of variations in velocity. JMO

That may well be reason for what you have personally experienced with the a/c jet effect range being greater than anticipated Sander. That, BTW was an excellent catch on your part

What you have to watch for as well is that different filters fit differently sometimes. I've seen situations were the filter mount flange rubber interferes with the air correction jet passage.

Most people never consider those things. Just pop on a filter and go, taking for granted that everything was designed 100% correctly. That's generally a mistake to assume anything after market is 100% correct

Always a pleasure to discuss concepts with you because you take an intelligent approach to everything you do on your motorcycle....and believe me. IT SHOWS!

larrycavan wrote:

The air correction jet is what is isolated from the main flow stream. Not the needle jet.

To my way of thinking, that's better because being out of the main flow stream it's more of a constant atmospheric pressure feeding that air circuit.

Where as with the a/c jet being trapped within the confines of the velocity stack, the pressure would be more subjected to variations of pressure because of variations in velocity. JMO

That may well be reason for what you have personally experienced with the a/c jet effect range being greater than anticipated Sander. That, BTW was an excellent catch on your part

What you have to watch for as well is that different filters fit differently sometimes. I've seen situations were the filter mount flange rubber interferes with the air correction jet passage.

Most people never consider those things. Just pop on a filter and go, taking for granted that everything was designed 100% correctly. That's generally a mistake to assume anything after market is 100% correct

Always a pleasure to discuss concepts with you because you take an intelligent approach to everything you do on your motorcycle....and believe me. IT SHOWS!

I had not given much thought to how the air correction jet reacts to pressure differences. I understand it's job is to introduce some air to the needle jet so the bigger the more air in the emulsion. If Keihin moved it outside the bellmouth/stack it makes sense that it works fine with atmospheric pressure and does not benefit from pressure change with higher air velocity. That being said I don't know if the same rules apply for the VMs and the CRs, the latter being a much more sophisticated design.

Either way, it would be very difficult to make a stack for the Mik's that isolated the air jet. Injection molded plastic like the CR stacks - consider the tooling cost. I'd have to separately machine an aluminum insert, weld it into the turned stack, then drill it out. Dammit Larry, see what you've done, you even got me thinking about it...

The filter blocking one or more ports should always be checked with aftermarket pods. Added bonus of this stack/filter combo is this can't happen!

Just FIY I'm running 122.5 mains/O-4/.8 air jet/20 pilots right now and it feels pretty damn good!
Just a hint of roughness on nearly closed/trailing throttle, which mainly bothers me in tight corners where I just need a bit of constant throttle and don't want to upset the bike. Adjusting the air screw does not get rid of this. I may try some 22.5s and see what that does.

With Mikuni smoothbores, I like the idea of only filtered air going through the BS30-97 air jet.

Good Fortune!

dutchz wrote:

larrycavan wrote:

The air correction jet is what is isolated from the main flow stream. Not the needle jet.

To my way of thinking, that's better because being out of the main flow stream it's more of a constant atmospheric pressure feeding that air circuit.

Where as with the a/c jet being trapped within the confines of the velocity stack, the pressure would be more subjected to variations of pressure because of variations in velocity. JMO

That may well be reason for what you have personally experienced with the a/c jet effect range being greater than anticipated Sander. That, BTW was an excellent catch on your part

What you have to watch for as well is that different filters fit differently sometimes. I've seen situations were the filter mount flange rubber interferes with the air correction jet passage.

Most people never consider those things. Just pop on a filter and go, taking for granted that everything was designed 100% correctly. That's generally a mistake to assume anything after market is 100% correct

Always a pleasure to discuss concepts with you because you take an intelligent approach to everything you do on your motorcycle....and believe me. IT SHOWS!

I had not given much thought to how the air correction jet reacts to pressure differences. I understand it's job is to introduce some air to the needle jet so the bigger the more air in the emulsion. If Keihin moved it outside the bellmouth/stack it makes sense that it works fine with atmospheric pressure and does not benefit from pressure change with higher air velocity. That being said I don't know if the same rules apply for the VMs and the CRs, the latter being a much more sophisticated design.

Either way, it would be very difficult to make a stack for the Mik's that isolated the air jet. Injection molded plastic like the CR stacks - consider the tooling cost. I'd have to separately machine an aluminum insert, weld it into the turned stack, then drill it out. Dammit Larry, see what you've done, you even got me thinking about it...

The filter blocking one or more ports should always be checked with aftermarket pods. Added bonus of this stack/filter combo is this can't happen!

Just FIY I'm running 122.5 mains/O-4/.8 air jet/20 pilots right now and it feels pretty damn good!
Just a hint of roughness on nearly closed/trailing throttle, which mainly bothers me in tight corners where I just need a bit of constant throttle and don't want to upset the bike. Adjusting the air screw does not get rid of this. I may try some 22.5s and see what that does.

The rules of physics apply universally, no matter what carb it is. Air pressure is air pressure. Fuel is fuel.

One method takes advantage of 14.7 PSI and one doesn't.

I'm suggesting that it may be possible to improve the VM carburetor's ability to emulsify fuel in the needle jet reservoir. Nothing more. Nothing less.

2 types of needle jets were used by Mikuni. Bleed type and primary choke type.

Bleed type in street carbs and Primary Choke type in dirtbike carbs.

Also the stock 26 mikuni's had a dual pilot fuel circuit that switched back and forth from passing fuel or air as throttle position and engine speed changed.

Stock VM's had better pilot circuitry than the smoothbores did. But then again, they were focused on smooth transitioning and NOT on making HP.

Race bikes don't give a rats ass about 2000 RPM throttle glitches but street bikes do

We use the techniques of racing to make street bikes into race bikes then want all the civility of the stock motor

Close is all you're going to get....

Larry C