SLUK has heard rumours about a forthcoming BGM kit with built-in reedvalve for a while but this spy shot is the first time we’ve seen it in the flesh.
Sticky – author of the Complete Spanner’s Lambretta Kit Book – reads the tea leaves to make some ‘Mystic Smeg’ predictions…
From the ribbed texture, these look like prototypes made using 3d-printed sand moulds. They are un-machined but you can still tell quite a lot just from one photo:
- The numbers cast inside the reed housing (65 and what looks like 70) suggest the piston sizes for both small block 195cc and large block 225cc versions
- The inside of the bore shows a boost exhaust port above one of the transfers
- Triple exhaust ports permit greater exhaust area than a single port, offering a route to increase power output without increasing operating rpm
- The reedvalve inlet looks like it uses a relatively compact reed positioned away from the piston like the ever-popular reedvalve conversions to piston-ported kits like the RT and Mugello. In this sense, it’s closer to a Quattrini M210 than a TS1 or RB on layout as the carb is on the flywheel side.
- Looking inside the inlet it suggests there may be at least one ‘Boyesen port’ feeding from the inlet direct into the transfer feeds
- The angle of the carburettor appears to be at 90 degrees to the frame tube. Hopefully, this will maximise clearance between the carb mouth and the panel sufficient to fit some form of hose and filter, at least on S1 and S2 machines
- The exhaust outlet is clearly angled back towards the wheel like that of an RB. Presumably, this was to allow sufficient length in the port for the exhaust boost ports to blend in. The upside is improved power potential. The downside is that you can’t swap an old RT kit for this one and keep the same exhaust. My expectation is that BGM would provide an alternative exhaust manifold to work with the BGM BigBox. Without that it will require a dedicated exhaust system
- The bad news is that the un-machined, unplated state of the prototypes suggests that they are still a long way from production because test and development will still take some time. I’d be surprised if these are available to buy before 2024
We’ll bring you more information as we get it…
Sticky
It might be an optical illusion (and we only have one photo), but are the reed valves at different positions? It looks like one sits North/South and the other East/West.
I can’t think of a good reason for this, so perhaps I should go to Specsavers (the one in Bishop Aukland is very good, I hear)