vespa pks 136 cutdown in pieces
vespa pk 130 yard bike in pieces
on reflection, Max can't be Italian, as he no longer agrees with the following:
<every scooter could do with a pk/px horncover & yankee seat>
Just out of interest now,why did you go for a reedvalve now and just not use rotory valve if not wanting to go that fast?
Rotaries do work really well. I know that Tony's Gp4 makes excellent power over an impressive rev-range, but I think I have worked out how Tony has done this, and it sounds like a lot of work. It also requires a lot of experimenting. Whilst a rotary valve has some characteristics of a disc-valve, with optimised opening and closing times, it does take some effort to find the best port timings. This can be expensive and we needed to fit to a budget. Rotary valves port size is dictated by the width of the crank web, which makes ports narrow and somewhat restrictive.
The advantage of the reed valve is that the port can be opened up beyond the width of the crank web, improving flow into the crankcase. Futhermore, where the rotary valve has to open and close at fixed points on the rotation of the crank, the reed induction system can deliver fuel on demand. If the exhaust is well suited to the engine's pumping action, it can suck fuel/air into the top end of the barrel directly through the engine. This boost of fuel aids the power band significantly. The engine can only do this at certain rev-ranges, and only because the reed is free to open as soon as there is a drop of pressure within the engine loop.
The aim to make this scooter go fast, but also to learn from, and enjoy the development.
Get some more popcorn, cos there'll be more tales from the homestead soon.
So I modified the exhaust last night. The wheel can now be fitted with the header pipe in situ, which is good news. I altered the bracket as well and the exhaust is secure. I have given it some more paint. The exhaust comes rather close to the wiring for the voltage regulator, so we might extend the loom by a couple of inches to stop any risk of chaffing. That was at midnight last night.
A club meeting has stopped us playing tonight, and Will has been cramming from some exams tomorrow.
Perhaps Thursday night we will have the scooter fully together, as long as the carb sits comfortably in the frame.
Did I mention that we are installing the engine while the whole scoot is upside down? It seemed like a good idea, until I got to thinking about how we are going to get it the right way up. Still, the installation of the control cables was a doddle.