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View Full Version : velocity stack vs. air filter



Trevor04
04-04-2012, 9:21 AM
I currently have the stock air filters on my 71 Bonneville but i dont like the look of them and they dont fit well so im trying to decide between a pancake air filter or other air filters or a velocity stack. do velocity stacks allow alot of dirt and dust to enter your carbs, and also is it necessary to change jet sizes or any other carb adjustments when you run stacks. thanks

Sighless
04-04-2012, 10:19 AM
I'm not sure on British bikes. But my experience velocity stacks on jap bikes is they suck! Not really but the problem (in my exp) is that they allow a lot of air flow while accelerating; but when you're trying to cruise at a certain speed they cut out and flood making the bike run like shit. Also with the carbs pointing towards the rear of the bike when you are riding in high wind they don't get enough air. As for debris getting in through, I ran really fine stainless steel screen, kept out most of it; but it will allow fine dust through (I live in NE we have a lot of it) but it's the same dust that plugs up my pod filters. So basically great for accelerating, not so much for regular riding.

Again I have only used them on jap bikes, a 2 cyl and a 4 cyl and I have replaced them on both bikes with pods. Not as attractive; but far less troublesome.

CRFyou
04-04-2012, 11:24 AM
I've not had any problems with acceleration/cruising speed with velocity stacks.

The amal carb seems to be pretty forgiving with all that airflow. Obviously it lets in larger debris than an airfilter.

My handsome buddy actually determined that those conical air filters were actually starving my bike of air.

GreaserMike
04-04-2012, 12:03 PM
I use pancake filters on my stock T120, velocity stacks on my chopper and little cone K&N filters on my flat tracker.

Like Branden said, the stacks do (obviously) allow more debris into the carburetor...which could lead to gunking them up, preventing the float needle from seating correctly (which causes gas to piss out the sides of the carb) or in more extreme cases scoring on the slides and accelerating wear & tear on the topend. Does any of that stop me from using them? No, of course not....but I accept the extra little headaches that go along with it. So really you just need to weigh looks over a little bit of dust getting into the carburetor.

Going slightly off topic, K&N type filters (and other aftermarket types) can be sprayed up with filter oil which traps even more dirt but for a street bike that's REALLY extreme (unless you live in a dust storm prone area.) But, for flat trackers and dirt bikes, that oil is a must.

jtbros
04-04-2012, 1:59 PM
I use stacks on my T140 but I putted some foam from a dirt bike airfilter in it . I sort off stitched it to the gauze of the stacks so no fine dust gets in.

ODBean
04-04-2012, 2:25 PM
I switch back and forth from stack to pancake depending on what type of riding I'll be doing. I have not noticed any difference in performance with either the the stacks or the filter. The stacks just look killer and sometimes you have to dress to impress. (more like bar whores like shiny things). So whatever floats your boat will work just fine.

Trevor04
04-04-2012, 2:39 PM
great info. i love the look of the stacks so i will probably go that route. but im going to try to get ones with the screens in them. i live in ks and its pretty damn windy all year long but especially spring and summer. do you guys use side covers or just let the frame show .

GreaserMike
04-04-2012, 2:45 PM
great info. i love the look of the stacks so i will probably go that route. but im going to try to get ones with the screens in them. i live in ks and its pretty damn windy all year long but especially spring and summer. do you guys use side covers or just let the frame show .

I'm guessing you have a relatively stock OIF Triumph that still has a swingarm. You can get aftermarket side covers that look like the pre-oif oil tank and toolbox. It is a straight bolt on and you'll hide the battery box. Plus, they look so much better than the ugly square airboxes and triangular steel side plates.

http://www.lowbrowcustoms.com/images/products/large_1874_side-cover-set-triumph-60s-style-oif-tr7-t140-photo-1.jpg

Lowbrow Customs carries them. LINK (http://www.lowbrowcustoms.com/index.php?l=product_detail&p=1874)


Here's a photo of my first Triumph - a 1971 T120 with those side covers, so you can see how they look:

http://www.chopcult.com/uploads_user/2000/1186/5634.jpg

(note the velocity stacks)

...and for contrast, here's a 1971 OIF commuter bike I had with no side covers:

http://www.chopcult.com/uploads_user/2000/1186/6201.jpg

Basically a super striped down bike to weave in and out of NYC traffic that I wouldn't care if it got knocked over. Even the back fender is plastic. (Note the cone type air filters, battery box is removed and it ran off a capacitor.)

sfmisfit
04-04-2012, 2:54 PM
running them on a bike at anything less than full throttle is placing fashion over function.

nothin' wrong with that of course, but don't expect your '71 Trumpet to last another 40 years without the air filters!

...the main issue with stacks at low rpm (as I halfway understand it) is the airflow is way too turbulent, which can result in a dangerously lean air/fuel mix—it's like trying to keep a candle burning on a windowsill with the windows wide open...


read Bill Rook's book "how to build a harley torque monster" for the technical explanation...you can google it for free....

TRUMPNUT
04-04-2012, 6:12 PM
Stacks straighten air flow . They work in all RPM's . Rember the guy is asking a question on Amals not some fixxed venturi carb like a S&S . If you open up a modern day sport bike stock air box you will see velocity stacks built in . If you care about debri hurting your top end rember these old bikes need new top ends at 10,000 miles so what if you only get 7,000 or so .

blackout
04-04-2012, 6:16 PM
i have stacks on my 91 shadow and it run like a champ. its all in the tuning. took some time to find the right air/fule mixture and jet sizes but when i got it all figured out haven't had any running problems.

Torch
04-04-2012, 9:32 PM
I prefer the look of velocity stacks,..... but then I make a living doing Triumph rebuilds...

Trevor04
04-06-2012, 7:37 AM
i honestly like the look of the flatter stock side covers that the aftermarket ones. but once i get rid of the air box i will have to attach them a different way. has anyone done this.

Speedfiend
04-06-2012, 5:36 PM
I made a set of side covers for my 71 BSA,(same frame as your triumph) I wanted to keep the flat boxey shape, but loose the air boxes. to go with the anglular shape of the tank, seat and front fender. I used the originl air boxes as a buck, added a piece of card board, rounded off the edges, smeared with vasoline and hand laid some fiber glass.
They mount like those after market covers.

http://i305.photobucket.com/albums/nn211/lamoreuxh/100_0168-1.jpg

http://i305.photobucket.com/albums/nn211/lamoreuxh/100_0627-1.jpg

And notice- a velocity stack!
No problems yet.

GreaserMike
04-06-2012, 6:49 PM
I made a set of side covers for my 71 BSA,(same frame as your triumph) I wanted to keep the flat boxey shape, but loose the air boxes. to go with the anglular shape of the tank, seat and front fender. I used the originl air boxes as a buck, added a piece of card board, rounded off the edges, smeared with vasoline and hand laid some fiber glass.
They mount like those after market covers.

http://i305.photobucket.com/albums/nn211/lamoreuxh/100_0168-1.jpg

http://i305.photobucket.com/albums/nn211/lamoreuxh/100_0627-1.jpg

And notice- a velocity stack!
No problems yet.

That looks like a million bucks! I think the shape works so well with the tank and dirt track tail...much better than if you had went with the rounded aftermarket side covers.

Torch
04-06-2012, 8:05 PM
Speedfiend... I've never been much of a purple guy (thanks to that little fagot Prince) and I'm not a big BSA fan but that is one good looking purple BSA. Nice job!.

Speedfiend
04-06-2012, 8:29 PM
Thanks guys. Yeah, nobody loves the purple, 'cept my daughter. I've been thinking about painting it black. I don't know... I can't leave anything alone.

starwolf
04-07-2012, 5:40 AM
...an alternative to black, .... Midnight Blue. Used to know a guy who had an old panel van(gutted out old ambulance) , it was Midnight Blue, though it looked black until your eye caught it in just the right light, then you realized it was blue, not black.

signal9
04-07-2012, 9:35 AM
Back to the stacks, suppose there's some cool filter alternative to try? Throw a sock over the stack, or tie a bandana over them? Something new to be adopted, overdone and ultimately bashed here on the forum?

robweeve
05-25-2018, 5:51 AM
" Also with the carbs pointing towards the rear of the bike when you are riding in high wind they don't get enough air. "

are you serious? LOL, if so then practically every bike with rear positioned airboxes/pod filters are starving for air. doesn't anyone around here monitor/edit statements like that?

Tattooo
05-25-2018, 6:29 AM
" Also with the carbs pointing towards the rear of the bike when you are riding in high wind they don't get enough air. "

are you serious? LOL, if so then practically every bike with rear positioned airboxes/pod filters are starving for air. doesn't anyone around here monitor/edit statements like that?

LOL So you believe that everything on the internet has to be true because it's on the internet??? WOW

datadavid
05-25-2018, 3:22 PM
Strong cross winds are actually noticeable(barely) when running pods or stacks. Not so that it hurts the engine though. I put foam socks on my stacks just because i got a fresh top end on it. Runs slightly richer and looks ugly as fuck but works great.

Tricky13
06-08-2018, 5:48 AM
I have both on my T160 but then i have the room.
https://i.imgur.com/OVGYL1j.jpg

hillcat
06-08-2018, 6:34 AM
" Also with the carbs pointing towards the rear of the bike when you are riding in high wind they don't get enough air. "

are you serious? LOL, if so then practically every bike with rear positioned airboxes/pod filters are starving for air. doesn't anyone around here monitor/edit statements like that?

No, we depend on people like yourself to correct. Not the Mods.
This is a very old post to be digging up. Maybe keep the corrections to more current posts.
I agree with your statement on "stern" mounted carbs.
That purple BSA will catch your eye.

Nanonevol
06-08-2018, 11:50 AM
Speedfiend... I've never been much of a purple guy (thanks to that little fagot Prince) and I'm not a big BSA fan but that is one good looking purple BSA. Nice job!.

"little fagot" huh? Nice talk. Prince liked girls far as I know - what's that say about you? How many people bought your records?

Dougtheinternetannoyance123
06-08-2018, 2:53 PM
"little fagot" huh? Nice talk. Prince liked girls far as I know - what's that say about you? How many people bought your records?

I have used often House of Kolor "Kandy Burple" which is a pretty amazing color and changes to a degree depending on lighting. From almost black to a Bright Bluish Purple. Had a shop customer tell me
"aint no way I will have fag purple on my bike!" But truth is, I sold a number of bikes with it, as well as shop customers picked it. Nobody complains and several said the color/paint job sold the bike.

Dodge makes a modern Challenger with a new updated version of their Plum Purple. Pretty bad ass car. While my favorite is the Orange and black layout I sure would have ZERO problems with a Purple Challenger. One sweet ride!

We are painting my wifes 69 Chevelle in Purple. Thats a given, but we are arguing about the rally stripes. I want a cream/alaskan white and she wants black rally stripes. I think she should defer to the painters expert opinion. (ME) She says "Do you want to keep living here?" so pretty much how thats going to work out. Unless you want your ass kicked by a girl, I wouldnt make fun of her Purple Chevelle.

Nanonevol
06-08-2018, 5:26 PM
Sure, it can be a good color. I never heard it was associated with a lifestyle. Sadly some people are still living in the Dark Ages or something. Now if you paint the bike in rainbows, you're making a statement!
https://i.imgur.com/bk8U61Km.jpg
https://i.imgur.com/5oE8SJfm.jpg

farmall
06-08-2018, 5:58 PM
We are painting my wifes 69 Chevelle in Purple. Thats a given, but we are arguing about the rally stripes. I want a cream/alaskan white and she wants black rally stripes. I think she should defer to the painters expert opinion. (ME) She says "Do you want to keep living here?" so pretty much how thats going to work out. Unless you want your ass kicked by a girl, I wouldnt make fun of her Purple Chevelle.

Black vanishes and doesn't make the purple "pop" while showing every speck of dust, but as they say "you can be right, or you can be happy". Go for happy, shoot it black and avoid the asskicking.

Stacks vs. pods? Pods flow worse (there's good reason for the elaborate stock Jap airbox designs on their modern machines) but on a chopper who gives a fuck? It ain't a racer and pods are convenient for maintenance.

What velocity stacks do not do is stop backfires from igniting extra fuel which may result from flooding. I won't run them on the street but I'm ruthlessly practical. Putting out a couple of customer bikes reminded me why I roll like that. I keep a soaking wet t-shirt handy when tuning a bike with stacks. I've a fire extinguisher too of course but who wants to clean dry chem off an engine?

They don't stop dust and sand either but if you ride on clean paved roads that's no big deal.