Exhaust Stub End Conversion

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Cav
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In another thread a reference was made to the Avanti exbox exhaust. I like the look of it but it seems a tad expensive for me, especially with the international postage costs. It got me thinking about converting an existing exhaust into a stub end arrangement. I have an old AF Rayspeed box which is in good nick. Looking at it closely I reckon it wouldn't take much to cut the u bend back a bit and weld on a new piece near the removed flange end, then fabricate a new stub end connector. Wondering if anyone has a had an attempt at doing this? Or can one buy a stub end? I could then match the older converted u bend connection to the bought stub .Any thoughts out there?
Cav
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Ok so I've just found a stub end for sale from SIP. There are a couple of others out there too. Looks like this is a realistic option
Warkton Tornado No.1
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Apart from one occasion when Ancilotti 50 mm exhausts were marketed briefly in the 70's, I have always made my own version of a 'clubman' exhaust.

That way you can get what you want. The 'U' pipe can be short, the front cone Spring mounted with a slip joint, the side of the box can be cut for ground clearance (if you are not afraid to corner properly) & the rear can have a cone of the long type.

The bleed should be large enough which may mean adding a silencer.

The last version I made was even discretely fully rubber mounted.

Go for it!
gaz_powell
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I did it with an AF Fresco on a TS1.

Which I think is the same u bend as a clubman

Used a JL stub, cut the flange off the u bend. Modified u bend and put spring loop on it
I kept the same u bend to pipe joint but used a SLJ thick alloy clamp ( not a car u clamp)

I wish I'd gone a bit further and made the main chain case bracket demountable.
Cav
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Thanks for the responses guys. I'm keen to explore the 50mm rote as I have find a local (ish) fella who can pull very tight bends and produces 50mm exhaust elbows as a standard range, He makes exhaust components mainly for custom cars and hot rods, so I'm looking into what we can do with 50mm but he can also do diameters. I like the JL stub/manifold and they are quite cheap. I'll keep you posted.
Warkton Tornado No.1
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Although I mentioned 50 mm in respect of Ancilotti, it pays to get the best size for the motor.

What we set out to do when modifying/making an exhaust is to aim for the optimum whilst accepting there will be compromises.

For a start, these days we all know that a parallel 'U' tube is bound to be a worse choice than a tapered header. You might want to bear that in mind. Rather than have a 50 mm pipe formed, if you start with something smaller, you may be able to slit it & weld into a taper @ a later date. This was my intention with my last experiment @ only 38 mm but I never got around to it as the exhaust performed far better than I thought it would. No doubt there may be further gains to be had, but I intend on doing another version from scratch.
Cav
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I bought an orange Ancilotti in 1975 from Len Turners Scooters and had it on my early Jet 200 with a 30mm Del'O, standard 200 iron barrel, points and coil, and it went very well. A bit of points bounce at top speed but electronci kits were not really an option then. This exhaust and carb combo is an old school formula that I've more or less stuck with for years. That exhaust was 42mm but I've always been fascinated by the idea of a 50mm. I'm exploring the option of using reducers instead of a fabricated and welded taper. I'm thinking about a 42mm manifold, a 42mm to 50mm reducer (reversed) into a 50mm u bend with a modified connection to the Clubman box. I have laid it out and it's feasible Just wondering whether the step up in the reducer is too sudden instead of the gradual flow from a tapered arrangement. It's interesting stuff and having looked at the extensive work Mark Broadhurst as done on this subject I may be clutching at straws, but we shall see.
Warkton Tornado No.1
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Cav wrote: Fri Feb 12, 2021 9:46 am I bought an orange Ancilotti in 1975 from Len Turners Scooters and had it on my early Jet 200 with a 30mm Del'O, standard 200 iron barrel, points and coil, and it went very well. A bit of points bounce at top speed but electronci kits were not really an option then. This exhaust and carb combo is an old school formula that I've more or less stuck with for years. That exhaust was 42mm but I've always been fascinated by the idea of a 50mm. I'm exploring the option of using reducers instead of a fabricated and welded taper. I'm thinking about a 42mm manifold, a 42mm to 50mm reducer (reversed) into a 50mm u bend with a modified connection to the Clubman box. I have laid it out and it's feasible Just wondering whether the step up in the reducer is too sudden instead of the gradual flow from a tapered arrangement. It's interesting stuff and having looked at the extensive work Mark Broadhurst as done on this subject I may be clutching at straws, but we shall see.
Ancillotti's first mass produced exhausts based upon the OEM SIII were a crude multi-taper if the one I have in my garage is typical. Subsequently there was a production run of non-tapered 'U' pipes of 50 mm diameter. I also own one of those.

I think that it is generally agreed that a multi-taper section between the port & the 'box is beneficial.

Probably the easiest way to get what is desired is to acquire an exhaust from a 'crosser that will be multi-tapered & also quite 'complex'* in it's shape, which can be cut & shut to fit. The cones tend to be steep but can be made shallower with the addition of wedges. An alternative might be a 210 Villiers kart pipe.

The modification of secondhand expansion chambers is one method I have used which has the bonus of the sections being of a good grade of steel more suitable for two strokes than might otherwise be selected.

It's @ the opposite end where the 'reverse cone' needs to be thought through. Unlike the AF Rayspeeds, I have found that a much longer, shallower cone is far better which then creates issues with the kickstart being in the way. That said, adding a back cone is really worthwhile IMO.

Much depends upon how far you wish to emulate the advantages of a proper expansion chamber whilst maintaining the body section of an OEM exhaust.


* lots of bends routing the pipe from barrel to main chamber.
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