Tipo head on an 80.5mm bore might be an issue, depending on which head you have.
Stock tipo that uses the 39.5mm intake valve is from an engine with an 86.4mm bore, and the combustion chamber is approx 86mm across the centreline of the valves, obviously this wont work mounted onto an 80.5mm bore as the fire ring won't have a surface to seal on....
There is also a tipo 1372 that uses a suitable head, that comes fitted with 37.5/33.4 valve sizes standard, the combustion chamber is approx 80mm across the centreline of the valves, so made to suit the smaller bore engines and might in fact be a more suitable choice for your build.
37.5mm intake will handle a seat throat size of 34mm easily, stock is about 32mm
39.5 valves fitted to an "narrow" combustion chamber just doesn't work very well flow wise, the periphery of the valve is severely shrouded as it is too close to the combustion chamber wall.
Your choice of intake manifold and carburettor is "interesting"... that style of manifold doesn't flow particularly well, and the carby also leaves a lot to be desired from a performance perspective, both are primarily designed for economy and trying to maximise torque.
SteveC
