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velocity stack
Topic Started: Apr 23 2013, 12:09 PM (458 Views)
koban
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Prince
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I'm trying to decide whether to fit a velocity stack or not. The one's from Allen's performance need the carb machining which is not a problem. But if i don't like it then it might be. Some of the ones on eBay look like a cut coke tin. Porter bro's and bare bones both use them and my tuner rates them. The thing that puts me off is air filtration I've got holes in the air box and it can get dirty in there quite quick. So I thought I'd see what you chaps think.
Edited by koban, Apr 23 2013, 02:19 PM.
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jonny h
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this is how i roll!
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first off Allens performance are not the same company from 2yrs ago since the owner died. they are now a bunch of lieing peices of shit when it comes to any sort of machining work and i wouldnt trust them or anything they say ever again.

if your going to run stacks you should really ditch the air filter box so they can pull all that lovely air in.

for days when your on the road and not a lovley clean track have a look at these: http://ramair-filters.co.uk/ms-sock-filters/ms-007-motorcycle-sock-air-filters.html

there is a few on that page with different sizes (as in spacing between the hole centers).

i think you can get funny little filter end caps for stacks as well , but that ramair is the best choice.

hth

ps. did i mention not to touch Allens (im a wanker) performance
Edited by jonny h, Apr 23 2013, 05:29 PM.
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koban
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Prince
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Thanks Jonny you always come up with a good idea. I wouldn't let them machine anything. I spoke to one of them when I bought the carb didn't like his attitude or price and went elsewhere.
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stevenfuture
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I bodged one on my Mikuni VM44 for a while just to see, I put some photos up in this section, I used a 70mm id tube of aluminium put a flare on the end with a tea strainer to stop big chunks getting in, but not really sure what the best length is, so after a lot of runs changing jets a lot! I went back to a foam filter I didn't see any advantage in the power or feel of it, but the sucking sounded nice, maybe on a dyno if you can get the length correct then maybe you will see a small power increase but for the road is it worth it? for me not. easy to clean the filter for me as I've not got that air box any more, & would it work so well inside a box even if it has all the sides cut away?
Testiculos habet ingens et bene sedeant
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RB636
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Potato Farmer
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Ive found a stack to fit the VM44 with a bit of fettling as porter brother say you need one to see the 65rwhp, been too bust either working or riding though, might give it a go still!
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stevenfuture
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Go for it young man, & let is know what kind of results you get I'm sticking with what I've got for now, but I'm interested go know how it goes for you.
Testiculos habet ingens et bene sedeant
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koban
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Prince
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I've put the idea back a bit as I want to get the bike on the road. I found a formula to work out the correct length it was to measure the distance from the valves to the end of the carb to get the ideal length. The one I found for the carb was a set length. I have a spare carb and its had the venturi turned down to fit one.
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RB636
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Potato Farmer
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Will do, not holding my breath though!
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koban
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Prince
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The one I found had an added length of 25mm. how long was the porter brothers stack.
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RB636
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Potato Farmer
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No idea.. just read their 'stages' blurb and it said use a trumpet... Messed with a calculator a while ago to get the length I need for peak power.
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stevenfuture
King
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Having looked into this 'stack idea' I had a go, but from what I remember from the old days the length has a math's formula that's hard to fathom, but the old fashioned rule was : roughly the length from the valve seat to the engine side of the slide for max rev's/bhp & the longer it got the less rev's/bhp & more torque it gave, leaving the air jet open to atmosphric pressure rather than inside the tube of fast rushing air in the stack/bell mouth, but this is 1960's 2 valve motors tec, but after trying it I found no difference, but the downside of dirty gritty air will get sucked in & leaky valve seats will occur sooner than with an air filter, so back to a nice easy to clean foam air filter for me, you pay's your money & lap in your valve seats more often, so good luck with your efforts
Testiculos habet ingens et bene sedeant
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