Lambretta AF Rayspeed TS1
This is going to be a learning experience for me as I have never tuned an engine before although I have been building them for years. I just received my kit along with a new crank and reprofiled head from Taffspeed Racing in Wales.
The kit includes:
I ordered the kit directly from Taffspeed for 2 reasons. First - their site was very technical and explained things in a way that made sense to me and seemed very honest. Second - they provide a doweling process to align the head with the barrel so that neither the head or base gasket is needed. You can see the two small holes diagonally across from each other in the picture of the head above.
The kit is cast aluminum and is so much lighter than a standard barrel. The main differences in the layout is in the transfers and ports, exhaust port, and a huge difference in the air/gasoline mixture intake. The new intake is shown below and uses a reed valve to allow gasoline into the crankcase for primary compression. Typically Lambrettas are piston ported - when the piston passes towards top dead center the piston skirt passes an intake opening in the barrel and allows air/gasoline into the crankcase. The vacuum of the piston traveling up in the barrel sucks gasoline in below it. There is a small point where the intake is still open and the piston passes top dead center and starts to move towards bottom dead center after the spark plug fires. At this point the inlet is still open and gasoline can be blown back through the carburetor until the inlet closes by the piston skirt traveling towards the crank. While this happens very quickly if you look at a Lambretta running without the air filter tube it will be very apparent.
The reed valve is supposed to stop this by allowing air/gasoline to pass in only one direction. Once the vacuum changes to pressure as the piston travels down, the reed shuts and allows the full charge to remain in the crankcase. Below is a shot through the large reed valve intake into the barrel.
The piston is also very different and has a different series of cut outs to open the transfers at the correct time. There are also two smaller cut outs in the top of the cylinder which allows a "boost port" to suck gasoline directly off the carb when the intake into the crankcase is shut. The rings are deeper but not L shaped like a standard Lambretta.
Some work needs to be done to the casing end of the main transfers to take advantage of the kit. The shot below shows the casing transfer (green arrow) not lining up with the larger barrel transfer (red arrow). I asked about this on the BBS and decided not to fully remove it, but to blend it in to where it meets the barrel. It is very close to the cylinder stud hole and could weaken it if I remove too much metal. I'll post a step by step installation of this kit once I start doing the work.
As I move ahead with the installation I'll add pages to this section . Click the "next section" below for port matching