K2 4 into 2 exhaust (DIY)

[El__burro]

i am going crazy with the idea of "transforming" the 4-1 in the pics below to a 4-2.
I am trying to see whether or not anyone has attempted this and with what result?
Eventually i would need a 2 into 1 and a couple of muffler too.

I would consider part exchange

Regards
el__burro

[Johnwebley]

I would suggest a 4-2 system should be cylinders 1-4 and 2-3 on paired pipes,

 

 

[El__burro]

so its almost impossible as 1&4 wouldn't end up on the same side as they are short.
What about 1-2 and 3-4.

[matthewmosse]

I have a set of cb550 4 into 2 pipes, not yet got around to fitting them, I could possibly dig them out to photograph to give you an idea how it has been done though it will not get fitted for a while and the 550 isnt reallly the same in any case..... I think its made to do 1&2, 3&4 as pairs.

[El__burro]

That may be helpful.
 Thanks
El__burro

[Chris400F]

Here's a thought ....
Where does the collector box for your system sit relative to the centreline of the bike i.e. is it about in the middle or offset to one side?
If it is roughly central would it be possible to modify the collector box to add another outlet pipe on the other side to the existing one?
This would give you a 4-1-2 system which could then be fitted with the twin silencers (or mufflers) you presumably desire.
From the pic of a collection of parts it is difficult to visualise how the complete system would look when fitted to the bike.

[El__burro]

Good thinking Chris.
I guess it's time to fit it and see.
El__burro

[Rob.b (Rob Birkett - RIP)]

HI,

It's a pound to a penny bet that your collector is going to exit on the right hand side of your bike.  I think it is going to be really difficult to adapt the collector so that it can accommodate a 4 into 2 system.  However, having looked at the collector it seems to have a wide and roughly symmetrical layout for receiving the 'down pipes', so for what its worth here is my suggestion; Don't bother with the collector and cobble up something using your set of 'downpipes' and off the self parts, I have added a photograph of what I managed to make at home using my own 'downpipes' and parts from:

http://www.classicbikeshop.co.uk/

It took quite a bit of head scratching but I'm happy with the result. Not Cheap though I spent about £225 on it.

here is my 500

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Rob

[El__burro]

most probably you are right about the collector being located on the centre-right of the bike, I am trying to see if the downpipes I have can be diverted to 2 per side  without much struggle.
Your bike looks great and this is exactly what I am trying to achieve. (4-4) Just thought it will be easier getting to a 4-2.
Thanks for your suggestions,
please keep them coming.

el__burro

[matthewmosse]

I think 4 into 4 would actually be easier but cost more - 4 silencers not 2. I would think probably the 2 left pipes would need cutting and welding, or bending ( probably with heat ) to point over the other way, and I'd anticipate them having a bit of extra length needing trimming off that side as the'd no longer cross the bike. Then there is the issue of getting it chromed or painting or avoiding chrome dammage when bending. Not inpossible - I think I would start by trying to clamp the engine end of the right hand pipes in a massively strong vise using substancial and shaped to suit soft jaws made of a hardwood like oak then inserting a tight fitting bar or pipe with plenty of length and swinging on it . This was something I had thought about doing in the past and I might well revist over winter or spring if I embark on a cb500 project. My starting point would be a motad 4 into 1 system with a rotten silencer. The 'fun' bit will be measureing the length of all the downpipes and angles when on the bike to see how much bending or cutting and welding is needed.

[Chris400F]

The downpipes in the pic all look to be about the same length and the collector exit pipe has quite a bend in it, which is what suggested to me that the collector may be located centrally(ish) under the engine and that it may be possible to add another exit pipe and a second silencer. You still have the issue of fabricating suitable changes to the collector box and bending an exit pipe, but not impossible and working with what you have.

If you want to go down the 4 pipe route DK have listed in their online spares shop something described as 'Honda CB750 CB 750 SOHC 4x Finned Exhaust Collars & Header Exhaust Inserts ', see http://www.dkmotorcycles.com/used-spares/headers,_manifolds_and_studs_1/243128/. The accompanying picture shows a set of downpipes; if these are for a four pipe system then that would seem to be a good starting point for a 4-2 or 4-4 system.
 

[El__burro]

Today I've managed to set the 4 pipes to see if this "job" can be done.
To this stage I am concerned with how little floor clearance there is.
Is that ok?
By looking at other set up I think its  too low.

Thanks
el__burro

[Rob.b (Rob Birkett - RIP)]

Afternoon,

Yes they look too low, they are going to ground. I reckon that  it's going to be far too much hassle to make them work.  Best bet is to follow the advice of Chris400f and buy a set of standard four into four down pipes to use as a basis. You can sell your four into one setup to offset the cost.

Go for it.   

Rob

[El__burro]

Yeah, I thought so.
rather than spending over £100 for the pipes, I am thinking of trying to make them myself.
I found some material on ebay and some tutorials on YouTube.
I have worked out that (if successful) I will be spending less than £100,
learn something new in the process and eventually make some more to sell later on.
Has anyone ever tried to do this?
Thanks
el__burro
https://youtu.be/utkQf454ibQ

[royhall]

That guys a real expert. I have tried that technique a few times (not exhaust pipes though) and it takes expertise to not have the pipe necking down and making it oval. For what I was doing the ovality wasn't important, but it would look a mess on a bike. If you can find a local company with a mandrel bender, that's the way to go.