Scooterotica

i ve wondered for years why we dont have power valves, some have said that they cant be controled but this is not true so why do tuners stay away from the power valve?

I think the main reasons are expense, stud spacing (lack of room) and demand, as well as the technical hurdle of getting the PV, fueling and ignition curve to complement each other.

This is probably why when you see it, the whole lot (cylinder, PV, ignition etc) is grafted on from something modern where a factory has already done all the hard work and development.

Ground clearance could be an issue, its got to fit in-between barrel and stub. It might only put an inch into the equation but they are close to the ground as they are... It would be a good addition to a Lambretta, giving some bottem end back to a peaky motor...

Broady did a one off barrel using one and gave up on it in the end. He tried various springs, fixing the valve at various positions and all sorts and was generally disappointed with the results.

I think heat (and it´s dissipation) is also a problem on aircooled cylinders on this position..

Ian Hepworth wrote:Broady did a one off barrel using one and gave up on it in the end. He tried various springs, fixing the valve at various positions and all sorts and was generally disappointed with the results.

Wasnt that one controled by exhaust pressure rather that a servo?

i believe someone is looking at the this modification as we talk