Restricted exhaust as standard???

[Big J]

Has anyone else noticed that when you remove RH can and link piece, take a look down main pipe to front cylinder and you may notice that Mr Honda set up the square cut pipes for welding---welded them up---but not bothered to trim off the 25% of open pipe area blocking the exaust!!!???
Well I spotted it and I,ve just attacked it with a die grinder so I,m inticipating a power hike over the Easter holidays!!
John.

[Kev L]

Have a search of exhaust restrictor in the search facility to see how others have dealt with this over the years.
And welcome to the forum

[lloydie]

You won't gain power you'll lose it .
That is there for a reason .

[baycat]

You won't gain power you'll lose it .
That is there for a reason .

is it there to balance back pressure, please tell us o wise one.

[lloydie]

You won't gain power you'll lose it .
That is there for a reason .

is it there to balance back pressure, please tell us o wise one.

Correct .
The only restriction in a standard headers is the welds where they meat the engine .

[Big J]

I will give full report of any changes to sound, performance, fuel consumption and spark plug colour after the Easter holiday I promise. Meantime it starts and sounds great as per normal Firestorm.
John.

[Big J]

Easter now gone for another year....
Well, having rattled up over 400 miles last week 2-up, when I rode up the west coast road from Lochcarron to Kinlochbervie in mostly dry fine conditions, I,d say full marks for my little mod.
The way I see it, I could get by with a wodge of cotton wool stuck up one nostrel fairly well. However, with no restriction I can do everything better and easier and faster, (I,m sure its about 25% of diameter getting in the way!) Thats a LOT.
Same goes for my Firestorm!
My exhaust had a restriction due to the methods of mass production. Not a designed in restrictor.
I recon it runs better now.
I have not tried out top speed yet so you,ll need to wait a bit for that report.
Fabulous road by the way. Anyone needing advice on highland travels, just ask. Have lived up here for 33years.Crossed Trans-Canada Highway in 1984.
John

[VTRDark]

My exhaust had a restriction due to the methods of mass production.

So you have not considered that Honda put this in place for a reason then. If you had the one exhaust then this mod would be OK but you have two. If you done a before and after dyno you would see that you have most likely lost power at lower revs..but hey if it feels better then all is good. So now you have lost that restriction maybe, just maybe, less will be scavenged back into the combustion chamber. If it feels better now then maybe your carb tuning and valve timing / clearances is not precise so when you correct that you may notice a loss then and want the restriction back in place. What you have to remember is that when you adjusts / change something it then has a knock on effect elsewhere.

[tony.mon]

I always cleaned mine up.
The other side is completely open and so any additional back pressure would be minimal.
The scavenging pulse is triggered at the final exit exit point, isn't it?
If this restriction made (much or any) difference fitting end cans would also lose power, and they don't.
I think that it's just a price compromise- they have to cut corners somewhere to end up at an acceptable price point for the market.

[VTRDark]

We're talking about the half moon restriction in the splitter not the welds around the circumference of the pipes at the ends tony.

[tony.mon]

We're talking about the half moon restriction in the splitter not the welds around the circumference of the pipes at the ends tony.

I was aware of that....

[bertye]

I have looked careful at the supposed restrict. I am an engineer so look at thing different to most, and into this part as to how it would of been made. It is clear that it is not a simple quick way of making the junction and being lazy in not cutting the parts so the the hole is the same size as the pipe coming of. looking closely at the piece of pipe down stream, it is not just a cut tube but is bent inwards, which would of taken an extra manufacturing process to make. Why do that? Making a round hole in a tube is a simple to do and much simpler to do that welding multiple parts together. Others have shown the difference vie dyno testing, and has shown cleaning it out has affected the power carve, and not for the good. If it has worked out fine for you, then that is good, but most will wish they had not and hard to undo once cut out.

[chris freckle]

Clearly this is an old thread now but I will throw my thoughts in ! The piece that is blocking the the RH exit is the same size as the large crease in the LH standard silencer which is there to clear the chain, this allows the exhaust sound & flow to be equal on both sides of the bike.

[fabiostar]

i have both types. one standard and one with the welds smoothed and that extra bit trimmed off... if it makes a difference either way iv tried both and it must either make no difference or such a small one that my seat of the pants dyno cant detect it....

but each bike is different i suppose.

[VTRDark]

Think of it like a rudimentary EXUP valve which creates backpressuere at lower RPM's giving you more torque To see another example with twin exhausts and how they do it, yes it's a Harley but the principle is the same Harley Davidson Dynamic Exhaust System Patent but this is exhaust design / theory so there is no right or wrong way to a degree unless you are good at maths and understand flow dynamics and have a computer brain that can create simulations in your head etc during the design process.

Fabio you probably riding your bikes like your in the Grand National.