What did you do today? Cobba's rebuild

[Kenny]

Could I get the full 2-1-2 data for the Over system please Brian?

[cobbadiggabuddyblooo]

Header length is 500mm and I.D. Is 39mm. Measured Centre of pipe
Material is 1.5mm stainless.
The headers slot into the collector and has an open area length of 200mm inside before splitting back into 2
Link pipes have an I.D. Of 47.5mm and 600mm long centre of pipe.
The collector is the main thing you need to try and emulate with the pipe dimensions .



Here is all the plumbing but if you can, you should try to take a look at the way Over has made their collector.

[Kenny]

Thanks Brian
So they have parallel headers and link pipes?

[cobbadiggabuddyblooo]

The link pipes to the mufflers and collector are all 1 piece like a wishbone as in the 1st photo.
The other small drawing on that photo is the shape of the bend on the link pipes rising up past the swing arm.

The 2nd photo is a template of the header pipes.
Just remember your choice of exhaust should compliment cam timing and overlap.

I reason why changing the exhaust on a 1970's motorcycle didn't do much as they had very little overlap and most aftermarket systems of the time where really a waste of money.

[cobbadiggabuddyblooo]

Yes I made up a few templates of the Over, Nojima and Akra systems including dimensions and sizes.

Would you send me the dims fr the Akra?

The Akra system will be hard to explain with it's shape , taper , balance pipe and bends but I'll put up some basic measurements shortly.

[Kenny]

Brian when I meant parallel I mean no tapers so they start and finish the same diameters ie Headers 39mm start and 39mm finish.

[cobbadiggabuddyblooo]

http://www.bikeland.org/board/viewthrea ... 2778&FID=1

Who was I chatting to the other week chasing info on this???
All my bookmarks are still locked away in the dead computer and I haven't bought a new one yet.
But I found this which was 1 of the bookmarked sites.
It re enforces what I touched on in our chat earlier about valve overlap and resonant frequency of your air box.
Another plus with having the carbies enclosed into the chamber too is that your fuel bowl pressure will stay constant with the intake pressure and make for a more constant mixture.

[cobbadiggabuddyblooo]

Brian when I meant parallel I mean no tapers so they start and finish the same diameters ie Headers 39mm start and 39mm finish.

Yes that's correct 39mm I.D. With no taper or step in size on the header pipe.

[cobbadiggabuddyblooo]

Here is an outline of the Akra system.
Header length 800mm
450mm from start of header to the balance pipe ( 16mm I.D. )
Header Starts with a 35mm I.D. Which is 135mm long then
There is a Taper length of 75mm to a 42.5mm I.D.


The 2-1 link pipe is 400mm long with an O.D. of 52mm ( note outside diameter )

[coxylaad]

Just putting it out there I don't think paper is the ideal choice of material for an exhaust cobba

[cobbadiggabuddyblooo]

But it's easier to bend into shape than cardboard...

[Rich]

Thanks Cobba, paper or card is good for me, the bends may not look as good as stainless but at least I don't have to purge it for taping up

I assume it spring clips onto header stubs, can you let me know the length and ID of those as they are not clear enough to read in the photo.
Cheers

[cobbadiggabuddyblooo]

Ok the 46mm is the OD of the section that slides into the exhaust port and is 7mm long it then drops down to The 42mm OD of the main body.
The I.D. Obviously is 38mm and when the exhaust header is fitted into it , it butts up to the 7mm long section with a 35mm I.D. That sits inside the exhaust port.

So that 7mm section is wider on the outside ( to fit the port ) and smaller on the inside (35mm same as ID of header )
The flange plate has a tiny recess so the sleeve locates into it.

Or you can easily just do a flange with a sleeve like the Over and std trx set up.

Best to just measure the exhaust port and use the info above as a general guide. I find with the Akra system I currently have fitted I need to run 2 exhaust gaskets in each port otherwise you'll need to place a spacer on the stud between the nut and flange.

[Rich]

Ok thanks, stepped internally to match headers +7mm onto header length, OD for clamps and port.

[cobbadiggabuddyblooo]

Finished off the 220mm rear caliper set up today. GSXR caliper mount was sleeved down to accommodate the smaller 20mm TRX axle.
Might see if I can fit the speedo sensor under the swing arm on the front caliper mount bolt to tidy it up a bit.