Exhaust Twin

For all the Twins except the SFC, there have been three basic exhaust systems. The first type consisted of two down pipes and two 'cut-off' silencers — the second type consisted of two down pipes and two 'cut-off' silencers with a balance pipe just below the exhaust ports and the third type was the 'big, quiet' one with two down pipes, a balance chamber under the gearbox and two silencers.

Whatever type of system is fitted, it is absolutely necessary that the system fits, is undamaged, and does not touch any part of the machine except the exhaust ports and the silencer/balance chamber mountings. Gas tightness is essential too — without it, the machine will vibrate more than it should and some performance could be lost.

Starting at the exhaust ports, make sure that the exhaust stubs sit on new and uncompressed copper-asbestos seals. Everytime you remove the header pipes, replace the copper seals. Do up the cast alloy exhaust clamps evenly and progressively. Use the proper nuts and washers too. Do not be. afraid to use graphited grease on their threads to aid tightening. At the same time do not overtighten — you could strip the stud threads.

When fitting an exhaust system, offer each part up separately, grease the joints lightly and fix them loosely. Assemble the whole thing before you start tightening and adjusting. Use only the proper factory clamps and mounting brushes. Use of the wrong silencer rubber bushes can lead to exhaust fracture.

Tighten the system starting at the front, at the exhaust ports. The less complicated systems are obviously the easier ones to fit. There is little to worry about with the two earliest systems. The last 'big' system requires careful balancing of components side to side. Once you are happy the whole thing is 'up tight', start the engine and check for leaks and vibration. Places to look for are in the silencer to down pipe/balance chamber.

The early systems were lighter and less restrictive especially that fitted to the 750S. They were withdrawn because of the change in legislation in Italy; hence the 'big' system was introduced. Although the early systems are still available they are not factory supplied items. Apart from noise, the only disadvantage, the earlier systems are lighter, 'faster' and less prone to internal rusting, and provide more side cornering clearance. In the UK, you should expect the conical, Laverda-stamped silencers to rust through from the inside after about twenty months. It's the balance chamber which hits the road first with the 'big' exhaust machines! The second and third systems are interchangeable, but only as complete systems and not piecemeal.

Several two-into-one systems have been offered for sale for the Laverda Twin. No one replacement system performs as well as the factory fitted systems, although they are obviously cheaper. The Slater, Ricky Racer and Marving systems all require carburation changes. It is not possible to fit an SFC system to other Twins because of the difference in their frames. Do not use any other proprietary exhaust.

The SFC has been offered with a two-into-one megaphone and a twin silencer system. The twin silencer system using two short down pipes, a four-way cross-over balance and two kinked (Jota shape) silencers can just about be used on the road. It's noisy in the extreme. The two-into-one megaphone system uses two down pipes and a two-into-one megaphone is for racing only. Most SFC systems were "dull chrome' although proper chrome silencers were available.

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