The head on the GT200 is the GT Porcupine.
The head has its fins radiating from the centre of the head which helps to transfer heat from the combustion chamber more efficiently than the conventional Lambretta head design.
The head also has two options for spark plug placement, centre or side. Which ever option you choose there is a plug for the other hole.
Porcupine head, pictured below:
The reed block is pictured below showing the replacable reed petals:
The Inlet manifolds pictured below:
The GT200 Piston is the same piston used in the Yamaha 350 LC Power valve engines. There are 9 piston over-sizes for complete kit longevity!
The first prototype kit was fitted to Mik’s GP200, it was an un-bridged barrel and was first tried with an AF big bore box exhaust and a 25mm Delorto Carb.
Mik was instructed not to “run it in” to see how it would be if poorly looked after from new. It was also decided not to blueprint any of the ports and to just bolt it on.
It pulled from low down really well due to the reed and revved on nicely even though it was running a big bore exhaust. The exhaust was a few years old and the extra power soon finished it off. After trying an old JL4 for a while his new Franspeed race exhaust arrived. The “Fran Race” transformed the performance as you would expect, it still pulled extremely well at low revs but now revved out and had a nice kick as it hit the power band. It clocked 82.7mph on gps and still didn’t have more than 200 miles on the barrel. his gearing was 4.8 final drive.