Topic: Anyone tried running pods on oem velocity stacks?

[ajduke5]

I have read all the info I can on pods, oem airbox and velocity stacks. I was originally wanting to run pods but now appreciate that the oem stacks are vital. The anti pod looks good but my question is...

Could you just use the oem velocity stacks and attach the pods to the ends for filtering. Obviously jetting etc would be requied.

Many thanks, and please be gentle if this sounds stupid.

[DaveBarbier]

I'll bite. Someone can chime in and tell me I'm way off, but I wouldn't say the OEM stacks are vital but stacks in general. But putting filter material so close to the stack would make the stack not do its job properly. Too much turbulence too close for it to smooth it out.

I'd say this could be a fine option as long as you don't expect it to perform as well as the stock system. To me this doesn't seem any better than putting filter material on aftermarket stacks or by using K&N pods (which apparently have stacks built in.)


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1978 Honda CB550K

[flybox1]

I think you'd run into a space issue. 
Many cant fit pod because of the space between the carb body and the next downtube.
Why not just run a foam screen over the stock v-stack.  No spacing issues there.

[harald]

I have done it on my cb750 F with F2 motor.
First You have to take out the rubber in the pods out  and then put the original rubber stacks about less than halv an inch , about one cm in. You can put silcon around to ensure it is air tight but I have not done that.
From the picture it just fits touching the frame a bit.
How does the engine perform?. Much better and smoother acceleration.

[DaveBarbier]

Do you have the pods inside the rubber stacks? That seems to completely bypass the "velocity" part of the velocity stacks. With that bell shaped mouth being covered it's just a pod extension. Or maybe the picture doesn't show it well enough and that's not the case.

And, just curious, but much better and smoother acceleration compared to what? Don't want to start another "stock airbox vs" thread, just want to know what you have here.

Edit: Just want to add that I'm using Steel Dragon stacks with filter material behind it.


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1978 Honda CB550K

[harald]

The rubber stacks go inside the pods approx. one cm, but you have to take out the exsisting rubber in the pods.
The rubber stacks fit perfectly with no modification.
The carbs will not function well without the rubber stacks, something to do with the airflow, thats why I mount the pods on the rubber stacks. i will not go into the discussion about pods contra oem airbox.
Just saying I made the carbs function better with rubber stacks than without rubber stacks, when using pods.

[alacrity]

Harold thanks for posting this idea.
I also run pods on my cb550, and have had it running really well, but have thought of doing what you have done for similar reasons.  Could my sense of "really well" actually be "not all that great without the stacks?" Dunno. I like the pods for some pretty dumb (admittedly) reasons: 1- the arbox is now a really good place to carry tools and stuff. 2- I HATED the evil process of fitting and removing the OEM airbox when I wanted to/needed to work on carb rack. 3- I like the off idle power I have now that very nearly emulates what one gets out of a cb650 with accel pump (knowing I may be sacrificing high flow/top end/high rpm power).
Biggest downside of pods had been: the drought in LA seems to be over, and pods suck in water when you get caught in a rainstorm, and my bike doesn't like running on water (at all).

Still... You may have arrived at the perfect hybrid solution.
Can you please give more specific detail regarding your "functions better" report?  Like at what throttle positions and load? Idle? Jetting differences? Did you run 1/4 mile and time? Different speeds at same gearing and rpm on same road in identical conditions?  I am NOT doubting your feeling or sense of how this has gone for you... I would just love to read some more... (Forgive me)... Scientific reportage about the results of your "experiment." (And perhaps others would too before changing their setups?
Thanks

[harald]

From Hondamans book (My cb750 Book) page IV-2 it states;

The velocity stack directs the incoming air toward the center of the carb thoat, so the air horn area can create a donut-shaped area of still, quieter air that is used to lift the fuel into the throat area from the bowl area. This toriod of slower air is created where the narrower throat of the carbs slide area restricts the flow coming in from the larger air horn.
In other words if the velocity stacks are removed the air horn loses some of its effectiveness at generating this important still air zone, and  mixing problems will result.

Thats why only using pods will create difficult carb  tuning problems.

[DaveBarbier]

From Hondamans book (My cb750 Book) page IV-2 it states;

The velocity stack directs the incoming air toward the center of the carb thoat, so the air horn area can create a donut-shaped area of still, quieter air that is used to lift the fuel into the throat area from the bowl area. This toriod of slower air is created where the narrower throat of the carbs slide area restricts the flow coming in from the larger air horn.
In other words if the velocity stacks are removed the air horn loses some of its effectiveness at generating this important still air zone, and  mixing problems will result.

Thats why only using pods will create difficult carb  tuning problems.

True, but as stated hundreds of times in the past, they are designed to be used with the airbox and plenum to help still the air. But yeah, you're totally right. Velocity stacks are important for laminar air flow but I don't think they are better than a properly designed aftermarket stack. I don't like that you can deform the oem stacks and they could be prone to cracking because they're so thin. Like I said before, the K&N pods I believe have a velocity stack built in, just like you made, but they're very expensive. Someone on here cut one apart to show this. UNI filters and Emgo don't have this stack.

Just to finish up, I don't think one can argue that they made an intake setup to work as perfectly as Honda did from using pods, stacks, filter material, etc. It will be worse in pretty much all aspects, but HOW MUCH worse is the question. To me, who knows little about bikes in general can't tell the difference. So I'm all for using pods and stacks and something like your custom made setup.


---
1978 Honda CB550K

[PeWe]

Possible to find nice arrangements of velocity stacks and KN filter on Internet. Like this one....
http://www.kzrider.com/forum/3-carburetor/408059-velocity-stacks-with-filters-for-vm29-smoothbores?start=40

I hope to find out how to improve my KN pods fitted on VM29's, RC-2454.

[harald]

From Hondamans book (My cb750 Book) page IV-2 it states;

The velocity stack directs the incoming air toward the center of the carb thoat, so the air horn area can create a donut-shaped area of still, quieter air that is used to lift the fuel into the throat area from the bowl area. This toriod of slower air is created where the narrower throat of the carbs slide area restricts the flow coming in from the larger air horn.
In other words if the velocity stacks are removed the air horn loses some of its effectiveness at generating this important still air zone, and  mixing problems will result.

Thats why only using pods will create difficult carb  tuning problems.

True, but as stated hundreds of times in the past, they are designed to be used with the airbox and plenum to help still the air. But yeah, you're totally right. Velocity stacks are important for laminar air flow but I don't think they are better than a properly designed aftermarket stack. I don't like that you can deform the oem stacks and they could be prone to cracking because they're so thin. Like I said before, the K&N pods I believe have a velocity stack built in, just like you made, but they're very expensive. Someone on here cut one apart to show this. UNI filters and Emgo don't have this stack.

Just to finish up, I don't think one can argue that they made an intake setup to work as perfectly as Honda did from using pods, stacks, filter material, etc. It will be worse in pretty much all aspects, but HOW MUCH worse is the question. To me, who knows little about bikes in general can't tell the difference. So I'm all for using pods and stacks and something like your custom made setup.


---
1978 Honda CB550K

[harald]

Tests show that stock box does not create very much still air but lots of turbulens and  reduces airflow a lot, nor do pods. The best performance you can get (as in racing) are only with velocity stacks without a mesh or net. Since a mesh will create tubulens in front of the airhorn. (ask anyone who races). The reason why stockbox works better than pods is because with stockbox, you use velocity stacks. The only reason I put pods on my stacks is to take keep dust away.
Pods let more air in then a stockbox, but of course you can as Hondaman recomends make holes in the stockbox to let more air in.

The pods I use fits perfectly (F2 carbs) with the stacks, without deforming the pods.
Of course KN pods with built in  stacks are to better than only pods. The difference with my stack and pods solution and KN pods with built in stacks, is that my pods are further away from the stacks, therefor less turbulens and of course cheaper.