Topic: DWMS RACING CB550F SUPER REVERSE PORT! NEW ENGINE COLORS AND PHOTOS!

[Syscrush]

I am thinking about going with one large velocity stack on each carburetor instead of running two small ones on each.

BroJo, you know a LOT more about building motors than I ever will, but I have serious concerns about the tuneability of this configuration.

[FunJimmy]

Sorta reminds me of the local guy that just majorly reworked and changed directions of the ports on a late V-twin engine, with Keihin carbs, that should make between 170-190 hp..

Did Roger ever get that bike on the road?

[754]

 This one was just started since last fall, building what he now knows it needs to compete at Bonneville.. got a good look at it last Monday.. cool bike.. softail, with shortened upside down forks on the front.. 2 ..41mm Keihins...

[joeyputt]

I am thinking about going with one large velocity stack on each carburetor instead of running two small ones on each.

BroJo, you know a LOT more about building motors than I ever will, but I have serious concerns about the tuneability of this configuration.

Why do you have concerns about the tuneability Brother Syscrush?

[nickandkristy02]

i hate you..........but its a good hate

[Retro Rocket]

I am thinking about going with one large velocity stack on each carburetor instead of running two small ones on each.

BroJo, you know a LOT more about building motors than I ever will, but I have serious concerns about the tuneability of this configuration.

Why do you have concerns about the tuneability Brother Syscrush?

Probably because the single stack feeding 2 inputs takes away what a velocity stack is designed to do, that is  supplying a straight smooth flow of air, in that set up there are serious restrictions to smooth airflow......Looks good though....

Mick

[paulages]

The cam is ready to go I just need to polish it. I have never seen a blank for the 550 but if anyone hears of any let me know I would buy a few if the price was affordable. If there are cams available for your engine I totally agree with Brother 754 just buy one and spend more time on the engine somewhere else as building your own cam requires a lot of time and you will have a hard time building a cam that will outperform one that you can buy, of course there is the happiness of knowing that you built your own!

How did you go about modifying the cam? Did you weld up the lobes and re-weld the new profile? If so, how did you maintain a consistent profile? I'm prepared to be incredibly impressed, but remain skeptical...

[Syscrush]

Probably because the single stack feeding 2 inputs takes away what a velocity stack is designed to do, that is  supplying a straight smooth flow of air, in that set up there are serious restrictions to smooth airflow......Looks good though....

That's issue #1.  Issue #2 is that you're going to set up some weird resonances in there because you'll have each stack feeding a carb that's gonna go suck-suck-pause-pause - a stack is tuned to help induction at a certain RPM due to the way that the positive pressure wave radiating back from the closed intake valve bounces back from the mouth of the stack as a negative pressure wave.  You're going to have 180 degrees of crank rotation between the first and second suck events, then 540 degrees of crank rotation between the second and third - making it impossible to tune the length, and maybe hard to tune the metering of the fuel (not necessarily enough to matter).

I agree 100% with RR that it does look good, though.

Try it and let us know how it works out.

If you have probs with it, then maybe a pair of stacks siamesed together like this would still look cool but work a bit better:

[nickandkristy02]

Probably because the single stack feeding 2 inputs takes away what a velocity stack is designed to do, that is  supplying a straight smooth flow of air, in that set up there are serious restrictions to smooth airflow......Looks good though....

That's issue #1.  Issue #2 is that you're going to set up some weird resonances in there because you'll have each stack feeding a carb that's gonna go suck-suck-pause-pause - a stack is tuned to help induction at a certain RPM due to the way that the positive pressure wave radiating back from the closed intake valve bounces back from the mouth of the stack as a negative pressure wave.  You're going to have 180 degrees of crank rotation between the first and second suck events, then 540 degrees of crank rotation between the second and third - making it impossible to tune the length, and maybe hard to tune the metering of the fuel (not necessarily enough to matter).

I agree 100% with RR that it does look good, though.

Try it and let us know how it works out.

If you have probs with it, then maybe a pair of stacks siamesed together like this would still look cool but work a bit better:

the amount of knowledge on this site amazing

[joeyputt]

The only thing about that Brothers is that these carburetors are not dual throat all the way through from the front to the back, the dual throats are only in the rear half of the carburetors and the front half is open all the way across so even if I run dual stacks they would not individually feed each throat.

In the first two photos of the carburetor you can see how it is open all the way across the front with a single choke, the third photo shows the back of the carburetor.

[Retro Rocket]

Probably because the single stack feeding 2 inputs takes away what a velocity stack is designed to do, that is  supplying a straight smooth flow of air, in that set up there are serious restrictions to smooth airflow......Looks good though....

That's issue #1.  Issue #2 is that you're going to set up some weird resonances in there because you'll have each stack feeding a carb that's gonna go suck-suck-pause-pause - a stack is tuned to help induction at a certain RPM due to the way that the positive pressure wave radiating back from the closed intake valve bounces back from the mouth of the stack as a negative pressure wave.  You're going to have 180 degrees of crank rotation between the first and second suck events, then 540 degrees of crank rotation between the second and third - making it impossible to tune the length, and maybe hard to tune the metering of the fuel (not necessarily enough to matter).

I agree 100% with RR that it does look good, though.

Try it and let us know how it works out.

If you have probs with it, then maybe a pair of stacks siamesed together like this would still look cool but work a bit better:

the amount of knowledge on this site amazing

And you thought i was taking the piss out of you....

Joey, it looks as though it would be hard to design a correct velocity stack for those carbs, i know you definitely have the skill to do it but it would still be a turbulent design......Not that that really matters because there is nothing conventional about this build....{thats a compliment mate  }

Mick

[joeyputt]

I definately agree and for the best performance it would probably be better to run a filter across the front but I just love the way that big stack looks hanging out front!

[Syscrush]

The only thing about that Brothers is that these carburetors are not dual throat all the way through from the front to the back, the dual throats are only in the rear half of the carburetors and the front half is open all the way across so even if I run dual stacks they would not individually feed each throat.

Then don't sweat it - build something that looks good and hope for the best. 

[joeyputt]

The stacks will be mounted on plates that bolt to the front of the carburetors so they will be easy to change if I need to but I think they will work well enough for what I will be using the bike for.

I do always appreciate all of your opinions and knowledge!

[unitedguitar]

What if you ran an oval shaped velocity stack. It wouldn't even have to be a true velocity stack but more of an item just for the look. It would take some creative metalwork but I think you could probably handle it. Take one of the regular ones and cut it in half and then add some metal in between them to widen it thus creating an oval. With the exhaust and intake manifold work you have done I think you could definitely handle it. Just a thought.

[Flying J]

Are you going to have to rake the front end? It looks like that stac will hit the front tire. If you do and have the room you could make your stacks look like your exhaust.

[joeyputt]

My dads 550 is here and I got the measurements off of it and have plenty of tire clearance so I do not have to rake the front end.

I am going to start building the frame this week and am definately going to extend the rear and am thinking about raking the front end a little but I will have to set the front end up and see if I like the stock or raked look better.

[754]

I dont think the stack is an issue, just reform the carb end to fit the throat shape of carb.. if you think that is whacked, look at the top of a 2 barrel or 4 barrel for a v-8.
 
 Cam. mysteries..
 You turn  cam 1 or 2 or  degrees at a time, record lift readings. Then if cam is built up, you grind off the cam to same or new specs in small interavals, like 1 or 2 degrees.. then polishblend till smooth..
 been done (hard way, like that) for around a hundred years..

[Tintop]

You could also check out a Weber stack for a Formula Ford down draft.

[joeyputt]

I got my rims! The front rim is 4.25x17 with a 120 tire and the rear is a 7x17 with a 190 tire!

It was dark when I took these photos so I will take some more tomorrow in the daylight but here is what they look like.

The front rim.




The rear rim.

[Stev-o]

190 - nice wide meat! What swingarm will you use?

[joeyputt]

190 - nice wide meat! What swingarm will you use?

Brother I am still trying to decide on the swingarm, I have several steel and aluminum swingarms. I can not decide if I want to go with a polished swingarm or a painted one to match the frame and I am also thinking about building a nice braced tube one. Too many decisions!

[Stev-o]

ooh...polished, that gets my vote!
You can always ask us to help you decide.

[joeyputt]

Hahahaha! I like a polished swingarm too Brother! If I keep going like I am there will not be any paint on this bike except for the frame, tank and what is on the engine!

[the technological J]

any info on those rims?