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Premium Member
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Discussion Starter · #1 ·
I had to cut mine to fit my JE airbox on.Also what you have to do per instructions for the Breathless one.I used their directions and cut 1.5" off each one.What adverse affects would this give me if any?
 

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WHATEVER
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Now you need to curt off 1.5" of each headpipe :hidesbeh:

How does the seat of the pants feel?
 

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myvrodrocks
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air will not flow in as smoothly. Velocity stacks are rounded at the top like a funnel for a reason...you might as well toss them in the trash and not use them at all...

I learned about this when tuning Bass boxes for car stereos. You would be surprised what difference the shape of the opening can make
 

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Dilligaf
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Slammed Rod said:
I had to cut mine to fit my JE airbox on.Also what you have to do per instructions for the Breathless one.I used their directions and cut 1.5" off each one.What adverse affects would this give me if any?
Does the airbox include a shorter filter element? I don't see why you would have to trim the stacks unless you are running without an element or at the minimum a shoreter element. Either way it can't be good for the performance of the bike.
 

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The Hawk
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Velocity stack length is tuned to the engine characteristics to provide the best flow over the rpm range of the intended use. Stack length is affected by engine size, cam shaft design, exhaust design and length, and intake port size and length of the heads. There are a couple of web sites that have velocity stack calculators where you enter data and it spits out velocity stack length parameters. For my 1350 with the megacycle cams, SE heads, tuning for the 3rd wave it requires about a 10.5" or 11" intake length to the intake valve at the peak HP rpm of 8500- 9000. Interesting stuff but not to sure it appies to a setup with no plenum to reflect wave impulses.

Mike
 

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Discussion Starter · #6 ·
The Breathless and JE air box cover has a recess in the middle and when I went to put it on the stock filter cover hit the underside.When I put the flat cover I made to clear ,it was touching the longer stack ,completely covering it off.I looked up breathless's install instuctions and they said to cut 1.5" off each one to get it to fit.If I would have put the flat one on it would have sealed against the cover not letting any air in at all.
 

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Discussion Starter · #7 ·
DTHDOC said:
Now you need to curt off 1.5" of each headpipe :hidesbeh:

How does the seat of the pants feel?
Well before I had my overheating problem,it was runnig like a raped ape!The flat cover came off while I was riding and my bike went way lean really fast.I shut it down ASAP.Only went about 3 mile and had to hitch a ride in my buddies truck.I'm goin to re-thread the rod that goes in the T-body so I can get the cover on securely this time.
 

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Vmod sells the shorter stack(rear I think) as a separate item. I read in acouple places that one way to get back a little of the power lost when putting on the Rinehart 2-2 pipes was to replace the longer one with another short one. You can only use two of the bolts to hold it down and I have no idea if it really did any good but I have it in place anyway. If I had to shorten the stacks I would try to cut a section out oft the middle and epoxy the two ends back together to keep the ropunded top end in place.
 

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Discussion Starter · #9 ·
I'm going to replace the whole thing with shortened Stacks and individual filters.
 

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WHATEVER
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Slammed Rod said:
I'm going to replace the whole thing with shortened Stacks and individual filters.
Did you do this yet, if so how's it working out?
 

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Chrome is king!!!
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I've had the BP airbox with cut stacks for almost two years and haven't had any problems. I recently had my bike retuned and it's running like a champ. Here is my dyno sheet.

 
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