Advice on header connections.

[utopia]

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"

:spin:

[Nickj]

All of my pukka competition bikes (2T enduro's) has this kind of fitting for the headers and most didn't leak gas or even seep oil. It was also a just a bit easier to get the pipes off for the very frequent ring changes.
I don't see that it should be a problem.

[Mr Gazza]

Mate! You seem to be fighting a head wind!
I'm sure that the 750 Paso used a 2-1 system that would bolt straight on yours, maybe with just a bit of jiggery pokery to get a silencer mated.
I saw a second hand one advertised somewhere fairly recently for not a lot of gold. I'll have a bit of a look for it.
Or come to think of it a bespoke collector for that RoadRacing system that was for sale on here would do the trick?

[utopia]

Hmm .. yes I thought I remembered seeing the springy system used to retain expansion chamber exhausts on racing 2 strokes.
Although it does seem to me that relying on the springs (which can stretch/weaken etc) to provide an even sealing pressure around the joint , is a little haphazard.
I'm fine with spring connections where two pipe sections join but I'm less than convinced that it is ideal at the exhaust ports.
On the other hand, if the spring connections do work adequately it would save a bit of modding work and would also mean that I could fire her up with the new system on in the very near future, to see how it sounds.
Thanks for the reply, Nick.

ps. Did your bikes use the std, fairly rigid gaskets ?

[utopia]

Yes, I do tend to fight headwinds.

Did I mention that the Sil Motor is a hi-level system ?
I began by considering fitting the low-level single can system from the 600SS but then I discovered that their header/collector pipes were plain steel, not stainless .. and most rotted away years ago.
Somebody on a Ducati stand once told me that stainless aftermarket systems used to be available for the 600SS, but I've never found one .. and they're low level too.
Dunno about the Paso but again, I suspect only low-level systems were available (and probably would require more mods needed to fit a monster than my Sil system might need).

It will be a headwind though ... I didn't mention how battered (and crudely shortened) the carbon can is, did I ? Only the end-caps will be useable, I reckon.
But the whole system is sitting on the bike now (albeit with the front header sawn in half) and it just looks the dog's.
I even have a bit of a fetish going about the little "Sil Motor" engraving on the silencer end-cap.
I think its going to have to be a labour of love .. in a headwind.

[Jez900ie]

I have a Sil Moto stainless 2 into 1 on my bike, though it bolts on and has a low level can. Like you you I think the unbalanced look is great, and it certainly sounds the part.

My Suzuki 185 Blue stroke exhaust is held in place with a spring and regular looking exhaust gaskets. It doesn't leak at all.

[Mr Gazza]

Paso would definitely only be low level with all that bodywork on the tail.
Sorry I can't help! Good luck... Hope the wind eases.. :mand:

[Dukedesmo]

Both my M900 and 916 have spring connected exhausts throughout.

The M900 as it is an aftermarket setup and 916 are like that from the factory. The benefits IMO are that there is room for movement/expansion.

As an example my old Guzzi has fixed into the heads exhausts and the left side was made slightly out of alignment - it fits but is under tension when fitted. The combination of heat & vibrations have caused the flange to split off twice; the first time I thought it was just bad luck/poor manufacture so I welded it back properly (only had minimal welding originally) but it pulled off again.

I then realised the alignment wasn't quite right (the curve of the pipe is not quite enough) so welded a new (thicker) flange on at a slight angle to compensate and whilst its' still not perfectly aligned (if it breaks again I'll look at bending it more) it is better and has lasted thus far.

My point being that spring fittings would allow for alignment/expansion/vibration and would never have broken in the first instance.

Also the Guzzi exhaust is mild steel whereas the Ducatis are stainless and I'm pretty sure stainless generally expands more with heat and is less flexible/more brittle so potentially the movement could be more of a problem?

Neither of my Ducatis have any leaking/sealing issues at the joints (at least not once warmed up) so I'd say the sealing is fine, on that I'd go with springs and flexibility given the choice.

[utopia]

... Hope the wind eases.. :mand:

Parp !

My preference for a hi-level system is partly because it makes the rear wheel more accessible for, eg brake, chain, tyre maintenance.
Apart from liking the looks, the other reason that I think I favour a longer pipe is because when I originally fitted the hi-level termi system, I thought it felt like it had improved low down engine response .. which I think also ties in with accepted theory.

Also, now that it is semi-fitted, I must admit that some of the scrapes look kinda cool.
They don't really matter functionally, as the pipe is stainless and corrosion isn't an issue.
I might not bother cutting out all the damaged sections .. just the badly dinged bit underneath .. and simply polish around the scrapes.
Patina, ain't it ?

[utopia]

Both my M900 and 916 have spring connected exhausts throughout.

The M900 as it is an aftermarket setup and 916 are like that from the factory. The benefits IMO are that there is room for movement/expansion.




Yes, I thought I remembered seeing it on at least one of your bikes.
Do they both use the same (relatively hard) copper/asbestos gaskets as the clamped-up system ?
And do the pipes have a flange at the end or is the joint at the heads made using just the square-cut pipe ends ?
Tbh, the ends of the Sil headers didn't look to be cut entirely square, against my engineer's set-square.

Not quite sure on the movement/expansion thing.
I see what you're saying but I'm not sure whether flexibility .. at the heads .. is the way to go.
I think I might prefer to focus on flexibility in the rearmost sections of the pipe, rather than the front.
Also, having seen the deteriorated state of the used springs which came with the system (which had stretched and bent their hooks) I'm not sure that I would rate springs as a reliable way of providing consistent "clamping force" at the head gasket.

Thanks for the reply .. all very useful stuff and definitely food for thought.

[350TSS]

My experience with spring retained exhausts is all with 2 strokes, 350 TSS Bultaco and TD3 250cc and TZ350 Yamsels. If I can remember correctly the expansion chamber fitted over about a 30/40mm long stub either cast into the barrel or, bolted onto a flange.
On the Bultaco when you revved it you could watch the header/expansion chamber pushing out about 10mm from the barrel against the retention springs. No gasket was used and it never seemed to leak exhaust gas. The one piece expansion chamber /header pipe was a good sliding fit to the barrel stub but I suspect the exhaust was really located/held in place by the Mini exhaust isolation mount under the foot rest.
On the TD/TZs similarly no gaskets used and again no issues with leakage. Longevity was not a concern as the maintenance schedule if you wanted the bike to stay competitive was:
150 miles change piston rings
300 miles change pistons, rings and small end bearings
450 miles change piston rings
600 miles change barrels, pistons rings and small end bearings
Repeat sequence every 150 miles until
1200 miles change crankshaft.
On my Monster I have a fabricated (MADASL) SS exhaust retained by springs into the exhaust ports in the head, the exhaust flange is about 8mm SS and is a snug but sliding fit over the 1mm wall SS tubular header. I think it is much more likely to leak exhaust gas because the pipe does not fit over a stub if the retention spring is deflected there will be a gap between the aluminium port and the SS header pipe. Mark Lumb (MADASL) did not recommend that gaskets should be used but I, like you, worry a bit about the end of the header pipe over time fretting the step, cast or machined (?) into the head.
If you want /need to make up your own can try these people
http://www.pjengineering.co.uk/categories.php?cat=9

[utopia]

Now that you mention it, I think I must have seen the "twangy" 2-stroke exhaust stubs in action .. possibly in a paddock somewhere, in the 70s, or maybe at a trials event.

And .. funny how you forget the most obvious stuff sometimes .. I once had occasion to test the performance of "washer-form" gaskets made out of alternate, concentric wraps of thin stainless foil and an asbestos-like material. The foil had a wibble in it too, which gave the gasket springiness.
They might be a tad softer.
As I type, I'm trying to summon a trade name. I do remember their works being in Heckmondwike .. well you would, wouldn't you.

Yes, I thought the MADASL systems used the spring method. Dukedesmo's is one of theirs, I believe.
And from your description, my Sil Motor system is exactly the same.

The Sil headers measure up at about 42.5mm bore, 44.5mm OD, so the wall thickness is only 1mm.

Twiddling with the Sil system, a realised that I didn't much rate the fact that there are only two springs at the header joints.
Even clamping pressure all round would seem to need the three legged stool principle to be considered .. ie a third spring.
But that would be too messy.
And then again, there are only two studs anyway .. but nevertheless I feel that either clamps or a third spring would seem adequate whereas just the two springs seems intuitively borderline.
On top of that, the springs on the front header of the Sil system both go to the same side of the anchor ring thingy .. which seems unnecessarily lop-sided.

350 Yamsel, eh ?
That makes the pulse quicken.

ps.
Maybe the ooomph in a 2-stroke exhaust is not so powerful .. and maybe the pressure at the stubs is lower than you might expect due to the "suck" from the spannies ....?
... so to speak.

[Yorkie]

I have a MADASL exhaust on my Monster and have a custom single side one being made for my SS Cafe Racer.

The fittings work really well and I have had no issues with leaking:

https://farm5.staticflickr.com/4556/38438948961_f2303f3d86_b.jpg (https://flic.kr/p/21yHEkk)photo_44_zpsff54c6f8 (https://flic.kr/p/21yHEkk)

They are lovely bits of kit.

Yorkie

[Dukedesmo]

Yes, I thought I remembered seeing it on at least one of your bikes.
Do they both use the same (relatively hard) copper/asbestos gaskets as the clamped-up system ?
And do the pipes have a flange at the end or is the joint at the heads made using just the square-cut pipe ends ?


My Monster setup utilises a short pipe inside the head, held on by the plate. This pipe seats against the existing surface so I use a conventional Monster gasket, this pipe has an ID to suit the OD of the exhaust (45mm) into it and has a small internal seating flange for the pipe to butt up against and the springs pull the pipe up to it.

916 uses a different manifold design (like an intake manifold) and has a flat metallic gasket between head and manifold, the pipe then sits onto the manifold pipe using springs, as per the joins on the Monster pipework.

Mine on the Monster is from Madasl so as per the pic in Yorkies post but if you want any pics of anything I can take them it is currently all off the bike because I've got the cylinders/heads off at the moment for bore replating.

[utopia]

Mine on the Monster is from Madasl so as per the pic in Yorkies post but if you want any pics of anything I can take them it is currently all off the bike because I've got the cylinders/heads off at the moment for bore replating.

Yes please, that would be spot on.
I think I can visualise the stubs and how they're clamped from your description but a pic or two would definitely be helpful.

I'm beginning to think that some sort of clamped up stubs with spring attachments might be the best way to go.
Possibly with tapered bores to smooth the transition twixt port and pipe.
The stubs would also eliminate the aforementioned tendency for uneven clamping via the springs .. they would now just be retaining a slip-joint, which sounds much more sensible.

I'm also starting to wonder whether my Sil system should have such stubs anyway, but I didn't receive them.
That might account for the minimal shortening that seems to be necessary to make the 900 system fit my 750.

Much food for thought though.
Its starting to make more sense now.
Thanks everybody.

[Luddite]

I found some pictures of Sil 900SS headers, which might have the same fixing method as yours.

https://i.postimg.cc/D0BFm2BN/Photo-Note-silmotor-900ss-exhaust-9505.jpg (https://postimages.org/)

These seem to have a small collar with the same ID as the OD of the header held within the exhaust port by the flange (just like Dukedesmo describes). The flange has two holes for the springs to hook onto.

These pictures show the collars and flanges in place on the headers and it looks like both loops for the two flange springs are on the same side, like you describe.

https://i.postimg.cc/B6fJV7jm/Photo-Note-Ducati-Silmotor-Exhaust-For-900-Ss-sl-1992-1997-8188.jpg (https://postimg.cc/CZJyZNH8)

https://i.postimg.cc/FztkGxvv/Ducati-Silmotor-Exhaust-For-900-Ss-sl-1992-1997-57.jpg (https://postimg.cc/7GVLZ0bt)

https://i.postimg.cc/mD1FQ50V/Ducati-Silmotor-Exhaust-For-900-Ss-sl-1992-1997-57-2.jpg (https://postimg.cc/dkv1F4QT)

So it sounds like your suspicion that you may have some pieces missing might be correct.

Hope that helps. :thumbsup:

[utopia]

Thanks for that, mate.
Helpful and informative, as ever.

Yep, that 900SS system is exactly like mine is at the engine end.
The loops for the springs are in exactly those positions.
So it does seem that I am missing a pair of stubs.
Well, who'd have thought it.
When I started this thread I had no idea that my system was incomplete.
I guess there's something (beyond the obvious) in the saying .. "you don't know what you don't know".

[Darren69]

A bolted up stub with springs would be the best option IMHO. Both of my 4 Valvers use that and Ive never have any leak issues and there is some inherent flexibliity to get things lined up easier.

If you've ever had to fit a 3 or 4 cyl inline system to a bike with just the bolted up headers with half rings you will know where I'm coming from! Getting them to all line to the collector up is a right skinned knuckles pain.

[Dukedesmo]

Yes please, that would be spot on.
I think I can visualise the stubs and how they're clamped from your description but a pic or two would definitely be helpful.



The system appears identical to Luddite's pics above.

https://www.ducatiforum.co.uk/data/photos/l/9/9695-1548591126-49dd012302d3f439eb1f3edb32ae6809.jpg

https://www.ducatiforum.co.uk/data/photos/l/9/9696-1548591137-20e984895db53e796aa6be56fa91fb10.jpg

https://www.ducatiforum.co.uk/data/photos/l/9/9697-1548591150-ab755c45c35ce0e8a82d93c00da55985.jpg

https://www.ducatiforum.co.uk/data/photos/l/9/9699-1548591169-bdbc52a4a1134966df98e95b4ad0fadf.jpg

https://www.ducatiforum.co.uk/data/photos/l/9/9698-1548591159-32f48254f0c3cc8be7d9837dbfe34408.jpg

As you can see the short pipe bolts solidly into the head with a gasket and the pipe slips in to be held in place by the springs. This allows some movement for heat, vibration etc, it also makes it easier to remove as you only need to unhook the springs and the pipe pulls out - OK rear exhaust is a bit tricky due to access issues but the principle is good.

If you want any measurements let me know or if you want to get your eyes or hands on it for any inspiration, you know where I am. :thumbsup:

[utopia]

Brilliant, mate. Thanks a lot.

So, it seems that I need to make some stubs.
I'm still uncertain whether to make these to be welded on to the system and bolted to the heads in the std manner, or whether to use springs .. but the springs are gaining ground as the likely option.
One issue that concerns me somewhat is the change in diameter from the exhaust ports themselves (around 38mm) to the 42.5mm bore of the header pipes.
I would like to arrange for the bore of the stubs to be tapered, to smooth this transition.
I don't yet know whether this will be possible while still being able to use springs.
I may have to design stubs that will fit inside the header tubes rather than outside .. and this may require the stubs to be welded to the headers. I dunno yet.
Maybe it can be done by just using some tapered reducers welded into the bore of the headers, and then simply copying the MADASL /SilMotor system.
Or better still, I might be able to take account of the reducing function in the design of the stubs and avoid the need for any welding at all (in that area at least).

I have now got my eye on an offcut of 316 stainless round bar on ebay.
Its 45mm dia ,, which I reckon is probably just big enough to machine some stubs from.
It might be useful to know the outside dia and overall length of your stubs Tim.
I can probably work out what's required, but some dims would clear the fog a little more.

[Darren69]

That MADASL system looks sweet. If I had a 2V thats what I'd be fitting. The issue with 2 into 1 systems is that you may lose some midrange, high level may get some back as the twin hi level does appear to improve the midrange torque.

I was reading recently some article or other that when Ducati used a 2 into 1 on the 999/749 bikes they experimented with pipe diameter on the rear cylinder to get the same tuned length on both. IIRC I think they ended up with 50mm front and 57mm rear in order to achieve the same tuned lenght for the Desmo valves to work at they're optimum. Food for thought, maybe?

[Dukedesmo]

It might be useful to know the outside dia and overall length of your stubs Tim.
I can probably work out what's required, but some dims would clear the fog a little more.

Stubs are 20mm long whilst the exhaust port 'hole' in the 900 head is 18mm deep and gaskets are around 2.5mm so the stub sits 4 - 4.5mm proud of the port.

OD of the stub is 48mm as is the ID of the port (give or take for loose fit clearance) and stub ID is 45mm - same as the OD of the pipe so that it sits nicely inside.

Original Ducati pipework is 40mm OD and the ID of my 45mm pipe is 40mm so perhaps if the Sil is the same you could use that to help with a 'slip' fit using a combination of parts from the Sil and standard exhaust?

Regarding a tapered system, with Desmoquattro Ducati it is generally considered the done thing to start out small and go larger down the pipework rather than fitting larger headers: Hence the 45mm - 50mm system on my 916, as large headers kill the back pressure and lose power, at least in the lower/mid rev range which is where Ducatis are tradionally strong.

As such big systems are normally only used in race conditions where top end is more important - everything else being equal 54mm systems make less power on the older bikes.

Presumably similar applies to the 2v and that maybe why most aftermarket systems for them appear to be no more than 45mm?

Also smaller displacement engines might suffer more from 'over-exhausting'? That said going to a single outlet may well redress the balance? Don't know how much research has been done into the pros/cons of size vs. number of pipes on 2v Ducatis?

[utopia]

Brilliant.
I have all the info I need for now .. now.

I was off out to the shed to have a further tinker but I had a slight distraction.
The high winds had blown two collared dove chicks and their nest clean out of the overgrown leylandii which towers over my sheds.
Yes, thats right .. two chicks in january.
Damn near fully fledged too .. they must've been born around christmas (sorry Gazza .. solstice) time.
Randy buggers, those collared doves.
Anyhow, out with the ladders and I managed to wedge the nest back in what seemed like a suitable position and replaced the chicks, still nice and warm, therein.
Fingers crossed.

Anyway, yes I agree with much of that thought on header design.
Though equally, I'm not sure exactly which way it cuts in my particular situation.
I was wary of the big bore headers and I was considering (and still can) fitting std size headers and blending to the bigger bore further along the system.
I may still do that in the end but, once I had the system in my hand, it seemed sensible to do minimum cutting on it for now, thus leaving maximum potential for later on.
Kind of "suck it and see while burning the fewest bridges".
In practice, it turns out that's the easiest way of adapting the overall dimensions of the system to fit my 750 anyway.

I'm gradually becoming convinced that, whatever the theory, there is a lot more than just theory involved in exhaust design.
Packaging on the bike is obviously one serious constraint.
Aesthetics is another, for the manufacturers at least, and in my case also (although I tend strongly towards the idea of form following function).
I've already mentioned issues around ease of maintenance.
Another thought might be that, given the 4kg weight saving by losing one of the cans, the overall performance of the bike might be increased despite the engine making less than its maximum performance potential.
Either way, the lighter system will score in the handling dept and also wins in the simplicity stakes.

The plan is to dyno test the first design and take it from there.
Tbh, I might start by refitting the Termis and dyno testing that as a benchmark.
Then after the exhaust is done the FCRs will go on .. so more dyno testing will be needed for those.
Its tempting to do exhaust and carbs at the same time but, although it would cost a lot more, I will learn a lot more from testing it at each stage.

[Flip]

Jeff, I 're have a pre-Ducati Performance system made by Gia.Co.Moto and that too is all held together with springs using little stubs that bolt into the head in the normal way with the remaining sections spring linked.

It's off my bike at the moment so if you want me to send you up the stubs to use as a pattern you're more than welcome.

https://i.postimg.cc/BvWbRCtY/IMG-3648.jpg (https://postimg.cc/4Y5X9V6V)

https://i.postimg.cc/5NR6SJJM/IMG_3650.jpg (https://postimg.cc/zVTzq93d)

https://i.postimg.cc/0N6G0nFV/Spaghetti-Header.jpg (https://postimages.org/)

https://i.postimg.cc/5yPM1fg9/IMG_4054.jpg (https://postimg.cc/QKWzJGvv)

https://i.postimg.cc/fW5sYvs4/IMG_4053.jpg (https://postimg.cc/z3L4rK3p)

I did think a while back about using it as a pattern to get a couple of systems made up to sell if there was enough interest.

Oh and what you might possibly loose by using the 2 into 1 system I think you will gain back by doing away with the restrictive squashed 'X' collector. By doing away with that on a 900 motor it certainly feels more peppy in the mid range and can apparently add around 5bhp .

[utopia]

Excellent stuff, Flip.
And thanks very much for the offer.
I'll see how things go.

Your system is interesting actually.
Am I seeing it right ? ... It looks like your stubs fit INSIDE the headers rather than outside .....?
That's the direction that my thoughts are going at the moment.
In fact I'm currently having a bash at machining up some adaptor sleeves that will enable me to do a mock-up assembly using internal-fitting stubs which are basically the cut-off ends from std headers (with further sleeves to adapt their 40mm OD to the 42.5mm bore of the Sil headers).
These are being made from the aforementioned rusty scaffold tube.
With any luck, using these I might even be able to fire up the motor briefly with the system reasonably securely fitted.

If your stubs are fitted inside the headers, could you measure the bore for me please ?
I'm wondering if they've attempted to blend the diameters of exhaust port and pipe as I mentioned before.

And yes, I think you have a point about the benefit of losing the X collector.
I'd forgotten about that.
Putting it all together, I reckon I would be unlucky to end up with a worse system than my current one .. which leaves the weight loss and simplicity benefits as gains.
Best case scenario might even be a few more bhp and better mid-range torque .. but tbh, my holy grail is only a meagre 70 bhp.
That's enough on the right roads .. but I do like light weight and a nimble chassis.

Where's the fingers crossed smiley face ??

[Mr Gazza]

Flip, we talked about your exhaust system quite a while back and you mentioned making a few sets then. Just to say I'm still interested if I am flush when you are ready to have some made. They look just the ticket, but I'm wondering why they are made in sections? surely they could be fitted in one piece, especially the front pipe.

Jeff, It might be useful to know about Every Exhaust Part, they might have some get out of jail free cards for your project? http://www.everyexhaustpart.com/cart/tube-and-exhaust-bends-and-elbows

[utopia]

Thanks, Gazza.
Though they were already on my radar.

Well, a 100mm long offcut of 50mm dia stainless steel popped up on ebay this morning.
That gives me a bit more room to play with, so I've nabbed that to machine some stubs from.

Last night I successfully machined one temporary adaptor stub from the rusty scaffold tube.
That's on the bike now, all clamped up to the head and with the header installed on springs.
Its fairly pukka.
Today I will attempt a slightly more ambitious version which will include the tapered blending between port and pipe diameters.

Turns out that the same rusty scaffold tube will also yield some temporary connector sleeves to reunite the system where I have cut it in half, to deal with the damage.
Furthermore, said damaged section turns out to have the same bend angle (and pipe dia/gauge) as one of the old link pipes that came from Capo's S4R .. so that will probably be drafted in. Thanks again, mate.

This is turning out to be a proper, forum based project now.
Which makes it even nicer.

[BigOz]

If your going for the weld on stubs it would be worth thinking about where they are going to be welded. If you weld around the back of the stub you could compromise the area the flange/clamp clamps down on and that could give uneven pressure on the sealing face.
Welding round the inside should be possible though tricky if the weld is too far up the tube.

Oh and 316 from your e-bay find to unknown possibly 304 tubing you want to specify ER309 or ER312 filler for that, if it is known 304 then go for ER316 filler.

[utopia]

Thanks, Oz.
For the moment, it looks like it'll be spring-fit stubs, at least for the first build and probably the final one too.
If I do go for welded stubs, they'll possibly be made from stubs cut from std monster headers, then sleeved (ie telescoped) up to full dia using a short, bridging tube of interim dimensions.
This will require two welds, but the end one will still be around 20mm from the flange, so hopefully far enough away.
And with luck, although I don't know exactly what material the tubing is, it should hopefully be all the same .. and weldable using normal exhaust-welding kit.

The ebay offcut is actually described as F51 grade, which is apparently a "duplex, 50/50 ferritic/austenitic grade.
Bit of a new one on me, that.
I'm not expecting to have to weld it though, as I plan to use it for the spring-fit stubs.
But I may change my mind. Do you know if this stuff is easily weldable ?

[BigOz]

Google tells me F51 is "UNS S31803 F51" and it is "readily weldable" looking at the composition it is similar to 2205 for which information is quite widely available but mostly covers it being welded to the same grade.

Welding to austenitic stainless such as 304 I have found no references yet so if I had to go blind I'd recommend Hastelloy W or Inconel 625 as a filler as these are good mismatched or unknown steel/stainless metal fillers. The issue with those is you really don't want to pay for either of them in small diameter filler, the price is excruciatingly high and they are difficult to get in small quantities in the UK.

Just checked 1lb packs are available in the US.

[Yorkie]

My single sided headers are nearly done:

https://farm5.staticflickr.com/4854/31968604357_1df55f8d09_b.jpg (https://flic.kr/p/QGXsiK)

https://farm8.staticflickr.com/7873/33034383368_22cd42b4b3_b.jpg (https://flic.kr/p/Sk8RgW)

Yorkie

[utopia]

Hmm .. having once again taken the hacksaw to my system, those neat welds are making me twitch.

Glad you've sorted that though ... I never was a fan of exhaust wrap, so I'm happy that it was only temporary.
That's quite a neat bit of pipery at the junction.

[utopia]

So, last night I finished the second (temporary) adaptor stub with the tapered bore.
Worked a treat.
I also found that I can fine tune the fit of the system by adjusting the effective length of the stubs.
This will be very handy, particularly as my first attempt at shortening the headers for the 750 (by removing 10mm from the rear one) had been a tad ambitious.

I then took the plunge and hacked off all of the damaged section from the front header.
I also hacked Capo's old link pipe (actually from an S4RS, it turns out) into a suitable length to replace the removed section.
As a happy accident, the connector sleeves on the end of said S4RS link pipes were cut off to yield a pair of close-fitting external sleeves which will enable me to temporarily join the pipes together during the initial re-fitting process, prior to welding.
With any luck I will also be able to use them, along with clamps, to hold the mating sections together during tack-welding (which will have to be done off the bike). I'll just drill three holes in the sleeves, to access the welds.

So, I'm off to the shed now with a collection of bits of pipe, hacksaw, file and cuppa.
And a bit of a grin.

A few days ago I was thinking that I might get this system modded and welded, ready to use by late spring.
The Weekender was a loose deadline.
I now rather fancy that I might phone the welder as early as later this week.
I love it when jobs go smoothly. Its often the other way round.

[Mr Gazza]

The wind's changed then?... :D

[Flip]

Flip, we talked about your exhaust system quite a while back and you mentioned making a few sets then. Just to say I'm still interested if I am flush when you are ready to have some made. They look just the ticket, but I'm wondering why they are made in sections? surely they could be fitted in one piece, especially the front pipe.[/url]

I can only think that being made in several pieces it gives the system some 'wiggle room' when fitting along with being much smaller to package but I too have got to thinking it might look better it is was a one piece front pipe like the original and the system Mark has made for Yorkie.

Mark at MADASL also did a Spaghetti system which currently he is not making but he might if there was enough interest so I am trying to get some comparative costs of copying my system by the people who made my little race bikes' exhaust and that from Mark.

[Flip]

Excellent stuff, Flip.
And thanks very much for the offer.
I'll see how things go.

Your system is interesting actually.
Am I seeing it right ? ... It looks like your stubs fit INSIDE the headers rather than outside .....?
That's the direction that my thoughts are going at the moment.
In fact I'm currently having a bash at machining up some adaptor sleeves that will enable me to do a mock-up assembly using internal-fitting stubs which are basically the cut-off ends from std headers (with further sleeves to adapt their 40mm OD to the 42.5mm bore of the Sil headers).
These are being made from the aforementioned rusty scaffold tube.
With any luck, using these I might even be able to fire up the motor briefly with the system reasonably securely fitted.

If your stubs are fitted inside the headers, could you measure the bore for me please ?
I'm wondering if they've attempted to blend the diameters of exhaust port and pipe as I mentioned before.

And yes, I think you have a point about the benefit of losing the X collector.
I'd forgotten about that.
Putting it all together, I reckon I would be unlucky to end up with a worse system than my current one .. which leaves the weight loss and simplicity benefits as gains.
Best case scenario might even be a few more bhp and better mid-range torque .. but tbh, my holy grail is only a meagre 70 bhp.
That's enough on the right roads .. but I do like light weight and a nimble chassis.

Where's the fingers crossed smiley face ??

Jeff, apologies but I haven't had much time to get in the garage this week- do you still want the measurements etc?

Let me know and I will dig out the box of pipes and get the vernier at the ready.

[utopia]

No worries, Flip.
I think I've sussed how your system works now.
It looks like the flanges are captive, in that they are held between the two end welds on the short terminal sections closest to the heads.
Thus the first short section of header tube is bolted to the heads, with subsequent sections connected to each other via spring retained slip joints.
This is a different set-up to the others which have a short, straight, machined stub bolted in via loose-fit flanges, with the first proper header section being retained to those by springs which connect directly to the flanges.
..... if that makes any sense.

I'm still curious as to whether there is a step where the headers abutt the exhaust ports on your system but its academic really so I don't think there's any need to go rummaging with the vernier .... but thanks.

[utopia]

Bit of an update ...

I've made the connector stubs.
The design includes a short section where the bore tapers from the 750 exhaust port dia to the big bore pipe dia, over about a 10mm length.
It looks "right" at least ... time will tell as to how well it functions.

I had a bit of a setback with the welding.
Last time I needed some welding done (beyond my personal skill level) I found a brilliant guy to do the job.
He actually had the exhaust from Michael Dunlop's TT BMW on the bench when I first went there, so I knew I had the right guy for the job.
But, 12 months later I find that he's packed up shop and gone to earn better money welding for Rolls Royce.
Bugger.
So, long story short, I've just got back from the car exhaust place down the road, clutching my newly welded system.
Actually its not fully welded yet .. I've left one joint just tacked so that I can do a trial fit and check that nothing has moved before getting the final joint welded.
I had to settle for mig rather than tig but the welder is a biker himself so at least he had the right kind of empathy.
The finished welds aren't too snotty and should dress up quite neatly.
As soon as I've finished my coffee and my bacon and brie panini, I'll be heading nervously out to the shed to try it for fit.
Wish me luck.

[utopia]

Update, part two ...

The trial fitting (before welding the last joint) went very well indeed.
In fact, I could detect no movement during welding whatsoever.
So, I've nipped back down the road and had the final joint finish welded.
And ....
It still fits like it grew there.
In fact, although the headers are a very close, sliding fit in the stubs, if I remove the retaining springs from the front header, it will slide smoothly in its stub if you tug it gently.
So everything must be pretty much aligned.
Whoopee !

Just two more hurdles to go now.
1) Does it leak at the stubs ?
2) How does it perform ?

I was going to do the valve clearances before I roll the bike out again but I might just have to start it ... and answer the other question which now (of course) occurs to me, namely ..
How does it sound ?

[Mr Gazza]

Sounds like you're getting there with it now. But you know the rules on here... Pictures or it didn't happen.. :D

Hope the sound is as good as your expectations.

[bigredduke]

Well done Jeff!

You must be exhausted.

[BigOz]

I had to settle for mig rather than tig but the welder is a biker himself so at least he had the right kind of empathy.


I'm hoping he used Stainless wire?

I've fixed a couple of jobs where normal/carbon steel wire was used on stainless it works and will hold, sometimes for quite a while but along with quickly rusting it will eventually crack along the toes of the weld.

If your going to be blending out the welds use clean fresh abrasives. Using abrasives that have been used on other steels can smear grains of the other steels from the abrasives into the surface of your stainless leaving you with stainless with rust spots after a while.

[utopia]

Well to be perfectly honest I don't remember asking, but that was because I was pretty sure that it would be stainless wire ... he only deals with stainless exhaust fabrication.

And yes, I have blended the welds (well 90% anyway).
I used a flap wheel that I have only previously used on ally.

Tbh, I feel a bit disappointed that I wasn't able to get some of your own welding work on the bike, for sentiment as much as quality, but the logistics of clamping it all up and then getting it down south without it moving precluded that, sadly.
The guy who did it works within walking distance of my house.

This has all got me motivated to buy myself a little tig machine and have a go myself in future.
Welding has always been one of those engineering skills that I have lacked (though I did dip my toe in the mig pool last year).

Latest news is that I fired the bike up in the shed and, on first impressions, it is "illegitimately" loud.
So I made up a little db killer type of baffle using a cone of Capo's left over perforated (stainless) core tube and nipped down the road to get it welded up.
Seems to work quite well and although it may not be a permanent fixture, it gives me options.

The sound is just as I had hoped .. not so much a harsh "brapp" but more of a bass "bwop" if you see what I mean.

A few pics will hopefully follow, once I've sorted out the "postimage" thing.