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Discussion Starter · #1 ·
Does anyone have experience with velocity stacks for amal carbs, specifically the longer ones with the mesh screen like on the lowbrow site? I have heard and read that they really arent the best for bikes used for 'regular' purposes and are really meant for racing. Any truth to this? Are they hard to tune for as it relates to going from a stock airbox (idle, mid range , etc.). I am asking for a brit bike but i dont think that really matters. Thank you
 

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This has been discussed before...Yes they are supposed to be used for race applications (without the screens), but I have several older bikes that have never had them fitted even from the factory. I have run one of my bikes with velocity stacks and twin carbs for the past 30 years and haven't had to overhaul it since 1986, and it's always been a cinch to tune....of course around here, the weather varies from swampy to somewhat less than arid and I avoid dirt roads like the black syphilis. If you live in a dry or even mildly dusty area, you ought to stick to air filters...the performance difference is practically unnoticeable anyhow, for us street riders, its really more about looks, or in some cases, originality.
 

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about 50% of the bike we work on have velocity stacks on them, there is nothing more to tuning them than there is to other type inlets, Most of the times it's all about the looks of the stacks. they look great so people run them.
 

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I like the way they look but was wondering if has made set that has a better filter than a screen? I want to keep my engine clean, but hate the way big air filters look.
 

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Discussion Starter · #6 ·
The velocity stacks that came with the bike stick out from the carb mouth (389 monoblock), at most, 1 inch. The ones from lowbrow for instance are certainly longer and are actually a 'stack'. I am wondering if the little ones I have are not really doing anything and inhibiting my tuning. I would think without the stock airbox (Norton Atlas) that the carbs would run lean so I have up jet some of the settings. I went up one setting on the idle as the bike was racing when at at standstill at a light and that helped, but the slide wanted to go leaner and the needle stay the same. I am fouling plugs now and it doesnt make sense and there is a 'dead' spot right off of the idle circuit when I go to roll on the throttle to take off from a light (sometimes it will cause a stall). This is why I ask about true velocity stacks which are longer than the short ones I have. It's a stock bike and the Norton carbs run side by side and not out at an angle like the bonny heads do, so individual filters aren't going to work like the ones from benchmark unfortuately. Thanks for the replys so far.
 

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In the past I have cheated a bit, wanting the look of a stack with some kind of filtration...what I did in that case was to stuff half an oiled stainless steel pot scrubber into the stack and wire it to the screen so it wouldn't get sucked into the carb throats...tuning was basically unaffected at all. Eliminates the 'real' reason for having a VS in the first place, but looks the part.
 

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If your going to run stacks, you really need atleast a foam and screen mesh on the ends. Running wide open stacks isn't a good idea no matter where you live. The screens alone are only going to keep out large debris, but they will still let all kinds of dust, bugs, gravel, etc... in there.

I run stacks on a dual throat Dellorto, but I have the foam filter screens on the ends. I'm sure they don't "filter" like a K&N, but the foam is just as thick as what comes on the "bugeye" filters. You retain the look of the stacks, but avoid the debris being scuked into the engine.

Sixball
 

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For years many expensive vintage motorcycles came from the factory with velocity stacks on them and back then many roads were unpaved.
If a Vincent was doing 60 MPH down a highway a bug or a rock would have to be flying at least 70 to make it into the rear facing carbs. at idle the slide is almost closed and not a lot of suction is going on.
Putting air filters on a Vincent or a Goldstar in like putting whitewall tires on a funnycar.
 
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