Everyone has experienced it: The disc valve has given up and the engine isn't working any more (especially when idling). Putting a defective disc valve sealing surface back in order is so costly, however, that the only sensible option is a radical conversion to reed valve control. In this area, repair kits offer a more straightforward solution.
The WORB5 kit consists of an LML reed valve manifold with a shortened end stop, a CNC milled adapter plate, a modified reed valve with 0.3mm carbon-petals and an M7 set of screws. It is fitted externally between the crankcase and the carburettor box. The reed valve then takes control of the opening and closing of the defective disc valve intake. To this end no (and/or minimal) work is necessary on the engine block and the total construction height (approx. 16mm higher) does not provide any problems on the frame. It is possible to continue using the original crankshaft and the SI carburettor. On engines with a small sealing surface on the crankcase these may have to be extended somewhat with external welding or 2 component metal.
Italian tuning experts DRT also offers a repair module for defective largeframe disc valves. The intake manifold is fitted with a high performance 3-valve reed valve and also has a big intake cross section. It is possible to continue using the original SI carburettor and thanks to the offset hole pattern for attaching the carburettor casing / carburettor there is no space problem in the frame. Together with a disc valve intake manifold from POLINI/MALOSSI/SCOOTRS which you can attach to the DRT intake manifold as a 'connecting piece' bigger tuning carburettors can also be used with it. To install the DRT kit, extensive modifications are necessary to the crankcase. On Lusso models, the components also have to be welded.
MAMO from Vincenza, produce a simple and cheap variety of disc valve repair as part of the SERIE PRO range. A rubber coated steel plate with a 0.3mm carbon fibre reed is simply placed between the carburettor box and the crankcase without modification to the inlet itself, plug and play!
Conclusion: The perfect solution on a defective disc valve!
SIP-TIP: Combined with the POLINI intake manifold disc valve (part no 21501100) the DRT intake manifold can also be ridden with carburettors of up to 30mm.