2-1 Exhaust IDEAS/ADVICE Help!!!

J

jachana

Been Around the Block
I am going to build a 2-1 setup on my CM400. I currently have 1.5" outside diameter exhaust tubing from the head and into the 2-1 collector. My question is should I run a 1.5" or 1.25" pipe on the other side of the collector to the universal reverse cone muffler? Any help would be great, i just want to make sure I am building up enough back pressure. Sorry for the gross drawing but you get the idea.

Thanks
 
hi there

nice drawing

the pipe after the collector should be bigger than the down pipes (headers).

I'm just building an exhaust aswell and have been through this aswell.
 
I feel the same way as you on the larger size after the collector, I am just worried that by using the larger pipe I will lose needed back pressure. How did yours turn out?
 
the pipe after the collector is always larger.
if you put a silencer into the exhaust you will get your back pressure.
but in any case you will have to rejet your carbs.

my bike I'm just building is a XS750 2D which will be a cafe racer so I have a 3 - 1 system.
 
I agree with the larger pipe and the baffle in the muffler. Is the reverse cone muffler pre-made or are you making that yourself? If it's pre-made is it a straight through?
 
I'm building the whole exhaust myself out of stainless pipe.
it will be noisy and good.
I will send some pics soon.
 
Do a google search on exhaust design.
There are dozens of books and websites out there that can help. You will need a slightly larger rear pipe, but just packing stuff into a homemade muffler doesnt mean youre exhaust will work correctly.
There are pretty specific constraints that need to be held to or the bike will never run to its potential.
 
As the guys have already commented, the rear pipe after the collector should be larger than the primaries (headers) and BTW, loud is NOT good.

Noisier than stock may be OK under teh right circumstances, but we don't need noisy pipes which do not save lives as has been proven before.

The right sounds is good and that may be slightly louder, but noisy is gunna hurt one way or the other.
 
teazer said:
As the guys have already commented, the rear pipe after the collector should be larger than the primaries (headers) and BTW, loud is NOT good.

Noisier than stock may be OK under teh right circumstances, but we don't need noisy pipes which do not save lives as has been proven before.

The right sounds is good and that may be slightly louder, but noisy is gunna hurt one way or the other.
Click to expand...

you are right it shouldn't be too noisy and there is a sience behind them exhausts.

whatever exhaust I build it will have to conform to the laws of that country and it will also have to be designed so that it works (but it would be nice if it spits a bit of fire).
 
I just want to add that the internal diameter of stock headers is usually smaller than it appears. If I'm not mistaken, the majority are double walled to prevent bluing of the chrome.

Anybody able to confirm this?
 
that's right again.
using a single wall down pipe with the same diameter should let the engine breath better, so a potential of more power if the carbs are set up correctly.
 
i hate to be the negative nancy here but if you're building "back pressure" into your exhaust system, you're doing it wrong from the start. a properly designed exhaust will cause the exhaust valve to open into a partial vacuum within the tuned range of the exhaust...
 
my exhaust is a 3(38mm) into 1(58mm) into 3(40mm) exhaust and it will be strait through.
at the MOT I will nick the hearing aid of my MOT tester.
it should be a doddle.
 
no, I don't. I'm just building it when I have a bit of time.
I will have to say that I had to modify the frame to get the exhaust in and it took a while and it's not comlpeeted jet.
I could send more pics later.
once the bike is done you could theoreticly lean it over further than the tires alow.
 
midnightcafe said:
NEED MOAR PICTURES!!! I have a pair of XS850's that I want to make into a cafe build. Do you have a build thread for the XS750??
Click to expand...

do you like the look of that?

I have 4 of them xs750's, they are great souding bikes
 
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