Advice on header connections.

[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]

Originally Posted by 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.

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.

[Dukedesmo]

Originally Posted by utopia

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]

Originally Posted by Dukedesmo

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.



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.







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

Hope that helps.

[Dukedesmo]

Originally Posted by utopia

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.











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.