Velocity stacks, pods, and advice

jsharpphoto

jsharpphoto

Coast to Coast
Newb here.

I'm working on a new-to-me 77 Superhawk. The previous owner installed pods (and i haven't opened the carb up, but i will assume that he rejetted accordingly). I'm going to be replacing the stock exhaust with dunstall replicas. I've heard that velocity stacks in a stock-to-mild motor can actually hurt performance, since it doesn't need that much air.

Is that true?

I'm happy to leave the pods on. I'm happy to buy velocity stacks. Putting the stock air box back on, really isn't an option. I can imagine running stacks on the street in a metropolitan area can mean I need to clean my system pretty often.

I need some advice from people smarter than me.
 
If you are going to ride the motorcycle frequently, I'd keep a filter on there. You will see how dirty the filter really gets. Then you will think twice about letting that directly into the engine.
 
acm177 said:
If you are going to ride the motorcycle frequently, I'd keep a filter on there. You will see how dirty the filter really gets. Then you will think twice about letting that directly into the engine.
Click to expand...

that confirms what I assumed. i've seen some people that run v-stacks with some sort of steel mesh screen. I assume that's like halfway between a pod and a stack? or maybe just a poor attempt at keeping shit out?
 
Velocity stacks with screens are to keep large items like rocks and small animals out of their carbs. For street riding its best to keep a filter on there.
 
My thought has been, if your setup works why mess with it. I actually run a stock airbox on my cb750 for this reason. It's an ugly piece of tuperware, but it works and I don't have to re-jet, or worry about running lean.

At least until I get tired of the look, that is. :)

It sounds like leaving the pods on is the way to go for you.
 
The metal screen keeps out birds and other large objects. It doesn't do a thing to keep dirt out of your engine. Velocity stacks look cool, but removing the air filters will definitely accelerate top-end wear.
 
Thanks for the advice guys, ill stick with my pods.

I'm trying to imagine a setup that would actually need stacks. Any mods that would push the engine that far?
 
I honestly dont think there's anything that would require you to 'need' stacks ever. even if you turbocharge the bike and run NOS you don't 'need' them, it's merely a compromise.

Top quality stacks might net you a percentage point, maybe 2. and only at a specific RPM (depending on the total length of your intake, from the end of the stack to the cylinder) over pods. the compromise for this extra power is the risk you take of sucking in a rock, bugs, or just loads of dirt into your engine.

I'd imagine they're great if you're racing, but even there I'd guess that if you went off into the dirt or sand you'd need to be prepared to rebuild the engine due to all the crap it would suck up into the combustion chamber.

In summary IMHO there is absoloutely no (good) reason to run stacks on a road bike, ever :P
 
thanks guys.

my pod filters are mounted to black rubber intakes into the carb. Is the length of that tube important? They're pretty long because they're designed to go all the way into the air box (that no longer exists), which means they're now just kind of hanging out in the middle of no where. Any reason I can't shorten the tubs to get the filters closer to the carb?
 
Jsharp - yup it is, on the below link, read the part about intake length - wave tuning

http://www.dotheton.com/forum/index.php?topic=39814.50

For a more simple explanation, the length of the intake determines at what RPM it's going to add it's maximum power due to something called the pulse effect. Without doing the maths, where it's going to add power is impossible to determine, because whilst shorter intakes will generally add power at higher RPMs, if it's too short the power will be so far past redline you'll never see it, and any additional power added below that will be so small you'd never notice it.

That being said, pods that look like they're in a different zipcode to the engine isn't the prettiest look either, and again shortening the intake too much is only going to rob you of a few percentage points of power
 
The only application that really justifies velocity stacks is drag racing. Any other kind of racing, air filters are de rigueur.
 
What is a 77 Hawk?
If it's a CB400T, they don't run well with pods, find a stock airbox and have a bike that runs properly
 
crazypj said:
What is a 77 Hawk?
If it's a CB400T, they don't run well with pods, find a stock airbox and have a bike that runs properly
Click to expand...

1968 CB77 Superhawk. It's an air-cooled twin, like the CB350, but the motor is stressed mount in the frame instead of a tubular basket setup like most CB's.
 
OK, I know what a CB77 is, CB72's big brother (first 'real' bike I fell off ;D )
The 'sloper' engines were much better looking but lot of people wanted more 'conventional' (British) styling
Great looking engine, Laverda copied style on 750 twin (in my opinion)
You have early slide carbs so they will work OK with 'pods' and be easy to jet properly
 
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