A while back I bought a slightly battered Sil Motor 2-1 exhaust system off ebay.
It has been badly grounded underneath such that the front header is scraped, dented and somewhat flattened, and there are other scrape marks on the 2-1 collector, but its the only system like it that I have ever seen for sale .. and as a bonus it was fairly cheap.
I have always considered that the second can is just unnecessary weight and complexity.
I also rather like the unbalanced look of a single can exhaust.
This system was designed originally for a 900, so I will have to shorten the headers and generally tweek the pipework to fit my 750 .. and in so doing I will also cut out and replace the damaged sections.
It sounds like a rigmarole but the design of the exhaust fits my vision for the bike far better than anything else I have ever seen.
One "problem" though is that it is a big bore system.
I wouldn't particularly have chosen big bore headers on performance grounds (I'm more keen to improve torque and low speed grunt than top end performance) but I'm prepared to suck it and see. I can always consider replacing the header sections with smaller bore tube at a later date, once the general fitting has been established (and if that happens, I would be looking at titanium rather than stainless .. but that's for the future).
Anyway for now, I am looking to just reduce the headers down to std diameter at the exhaust port connections, leaving the full length of big bore header pipe in place for now.
The connections at the cylinder head on the Sil Motor system are not bolted via ring clamps and half-rings as per std but are held in with a pair of springs attached to dummy clamps on the exhaust studs .. as I have casually observed on other systems over the years.
I am unsure whether to stick with this method of attachment or instead to weld in short stubs cut from std headers in order to reduce the dia down to std at the heads, and retain the std, bolted up fixing.
The latter might be favourable as it makes the process of adaptation to 750 dimensions a little easier.
It also blends the exhaust port to pipe diameter step favourably, in my judgement.
But, I was just wondering how those folk that have used systems with spring retaining attachment to the heads have found them to work in practice.
Do they seal adequately/properly ?
Do they use the same gaskets (which are presumably asbestos-filled copper rings) ?
Also, it appears that there is no end flange on the Sil Motor headers .. they just end in plain pipe. Is this how such systems seal against the exhaust port gaskets or am I missing some bits from my system ?
I can see that a thin pipe would give greater pressure on the gaskets and may therefore seal adequately ... but it just looks a bit dodgy to me.
Would I perhaps need different (softer ?) gaskets in such a system ?
Like I said, I probably favour converting to the std, bolted up arrangement anyway, particularly for a road bike where a reliable connection in the long term will outweigh the ease with which the spring-retained headers can be quickly detached for maintenance etc. That system seems more appropriate to a race bike than a roadster.
But before taking the plunge, I thought it sensible to canvass opinion from those with experience of the springy type.
Thanks in anticipation.
ps. I've weighed both systems and it looks like the new system will save around 4kg against my current one, which is std headers with link pipes to a pair of hi-level titanium termis.
With the new system, the total weight of the bike will then be on the cusp of dropping into the 150kg bracket (ie it may just scrape in at 159.9 kg).
Ok, the numerical barrier is only a psychological goal but I fancy breaking it nevertheless.
Right, I'm off to machine some temporary adaptor pieces out of an extremely rusty length of old scaffold tube that I dragged out of the bottom of a local hedgerow.
"Overground, underground, wombling free"
